chore: update version number to 0.1.82

VERSION

@@ -1 +1 @@
-0.1.79
+0.1.82

android/app/src/main/java/com/anonymous/bulwarkmobile/BulwarkFcmPackage.kt

@@ -15,6 +15,7 @@ class BulwarkFcmPackage : ReactPackage {
             add(BulwarkClientCertModule(reactContext))
             add(BulwarkDeviceSyncModule(reactContext))
             add(BulwarkWidgetsModule(reactContext))
+            add(BulwarkPdfModule(reactContext))
             // The bridge registers React Native's own module under this name.
             if (ReactNativeNewArchitectureFeatureFlags.enableBridgelessArchitecture()) {
                 add(BulwarkHeadlessJsTaskSupportModule(reactContext))

android/app/src/main/java/com/anonymous/bulwarkmobile/BulwarkPdfModule.kt

@@ -0,0 +1,143 @@
+package com.anonymous.bulwarkmobile
+
+import android.graphics.Bitmap
+import android.graphics.Color
+import android.graphics.pdf.PdfRenderer
+import android.net.Uri
+import android.os.ParcelFileDescriptor
+import com.facebook.react.bridge.Arguments
+import com.facebook.react.bridge.Promise
+import com.facebook.react.bridge.ReactApplicationContext
+import com.facebook.react.bridge.ReactContextBaseJavaModule
+import com.facebook.react.bridge.ReactMethod
+import java.io.File
+import java.io.FileOutputStream
+import java.util.concurrent.Executors
+
+/**
+ * Renders PDF pages to PNG files for the in-app file preview, with the
+ * platform's own PdfRenderer: Android has no PDF view, and its WebView
+ * doesn't show PDFs either. The preview draws the pages in a WebView of
+ * its own so they zoom, asking for each page as it scrolls into view.
+ *
+ * PdfRenderer is not thread-safe and allows one open page at a time, so
+ * every call runs on one background thread, and the open document is kept
+ * between calls for the file the preview shows.
+ */
+class BulwarkPdfModule(reactContext: ReactApplicationContext) : ReactContextBaseJavaModule(reactContext) {
+
+    private val worker = Executors.newSingleThreadExecutor { r -> Thread(r, "BulwarkPdf").apply { isDaemon = true } }
+    private var openPath: String? = null
+    private var descriptor: ParcelFileDescriptor? = null
+    private var renderer: PdfRenderer? = null
+
+    override fun getName(): String = "BulwarkPdf"
+
+    override fun invalidate() {
+        worker.execute { closeDocument() }
+        worker.shutdown()
+        super.invalidate()
+    }
+
+    /** Page count and each page's size in points: `{ pages: [{ width, height }] }`. */
+    @ReactMethod
+    fun open(fileUri: String, promise: Promise) {
+        worker.execute {
+            try {
+                val doc = document(fileUri)
+                val pages = Arguments.createArray()
+                for (i in 0 until doc.pageCount) {
+                    doc.openPage(i).use { page ->
+                        pages.pushMap(Arguments.createMap().apply {
+                            putInt("width", page.width)
+                            putInt("height", page.height)
+                        })
+                    }
+                }
+                promise.resolve(Arguments.createMap().apply { putArray("pages", pages) })
+            } catch (e: SecurityException) {
+                // Password-protected; PdfRenderer can't open those.
+                closeDocument()
+                promise.reject("E_PDF_PROTECTED", e.message, e)
+            } catch (e: Throwable) {
+                closeDocument()
+                promise.reject("E_PDF_OPEN", e.message, e)
+            }
+        }
+    }
+
+    /** Render one page `width` pixels wide into `outUri` (a PNG). Resolves with the file URI. */
+    @ReactMethod
+    fun renderPage(fileUri: String, index: Int, width: Int, outUri: String, promise: Promise) {
+        worker.execute {
+            try {
+                val doc = document(fileUri)
+                if (index < 0 || index >= doc.pageCount) throw IndexOutOfBoundsException("page $index")
+                doc.openPage(index).use { page ->
+                    val w = width.coerceIn(1, MAX_PAGE_PX)
+                    val h = (w.toLong() * page.height / page.width.coerceAtLeast(1)).toInt().coerceIn(1, MAX_PAGE_PX * 2)
+                    val bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888)
+                    try {
+                        // Pages are transparent where nothing is drawn.
+                        bitmap.eraseColor(Color.WHITE)
+                        page.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY)
+                        val out = fileOf(outUri)
+                        // The preview's folder is gone once it closed; a page
+                        // still queued then must not bring it back.
+                        if (out.parentFile?.isDirectory != true) throw IllegalStateException("preview closed")
+                        FileOutputStream(out).use { stream -> bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream) }
+                    } finally {
+                        bitmap.recycle()
+                    }
+                }
+                promise.resolve(outUri)
+            } catch (e: Throwable) {
+                promise.reject("E_PDF_RENDER", e.message, e)
+            }
+        }
+    }
+
+    /** Close the document the preview showed. */
+    @ReactMethod
+    fun close(fileUri: String, promise: Promise) {
+        worker.execute {
+            if (openPath == fileOf(fileUri).absolutePath) closeDocument()
+            promise.resolve(null)
+        }
+    }
+
+    private fun document(fileUri: String): PdfRenderer {
+        val path = fileOf(fileUri).absolutePath
+        renderer?.let { if (openPath == path) return it }
+        closeDocument()
+        val fd = ParcelFileDescriptor.open(File(path), ParcelFileDescriptor.MODE_READ_ONLY)
+        try {
+            val doc = PdfRenderer(fd)
+            descriptor = fd
+            renderer = doc
+            openPath = path
+            return doc
+        } catch (e: Throwable) {
+            fd.close()
+            throw e
+        }
+    }
+
+    private fun closeDocument() {
+        try { renderer?.close() } catch (_: Throwable) {}
+        try { descriptor?.close() } catch (_: Throwable) {}
+        renderer = null
+        descriptor = null
+        openPath = null
+    }
+
+    private fun fileOf(uri: String): File {
+        val path = if (uri.startsWith("file:")) Uri.parse(uri).path else uri
+        return File(path ?: throw IllegalArgumentException("not a file: $uri"))
+    }
+
+    companion object {
+        // A 4096 px page bitmap is 64 MB; keep well below.
+        private const val MAX_PAGE_PX = 2480
+    }
+}

docs/parity/03-email-viewer.md

@@ -175,7 +175,7 @@ RN has a solid single-message reader (WebView body with CSP, shrink-to-fit + pin
   - What RN does: single tap follows the global `mailAttachmentAction`; `jszip` is already a dependency (`package.json:36`) but unused for mail.
   - Fix hint: long-press sheet with "Open / Save / Share"; a "Download all" entry building the zip with `jszip` into `Paths.cache` then sharing.
 
-- [x] **In-app attachment preview (images, PDF, text, audio/video) is absent; iOS "Preview" is just the share sheet — fixed in d2ed27f** — `P3` — `partial`
+- [x] **In-app attachment preview (images, PDF, text, audio/video) is absent; iOS "Preview" is just the share sheet — fixed in d2ed27f; audio/video, HTML, Markdown, SVG, Android PDFs and ZIPs since 0.1.80-0.1.82** — `P3` — `partial`
   - What WEB does: `FilePreviewModal` for images/PDF (bytes handed to pdf.js, #871)/text/markdown/audio/video/eml, script-bearing types forced to download (`components/mail/mail-app.tsx:2887-2935`, `lib/file-preview.ts:29-92`).
   - What RN does: Android hands the file to an external viewer via `ACTION_VIEW`, iOS opens the share sheet (`src/lib/email-export.ts:64-79`, `115-141`); nothing is previewed inside the app.
   - Fix hint: for images/PDF/text open a modal `WebView` on the cached `file://` (or use `expo-file-system`'s `File.uri` with a QuickLook bridge on iOS); keep the external-viewer path as fallback.

docs/parity/07-filters-vacation-files.md

@@ -110,7 +110,7 @@ Filters: RN carries a byte-for-byte port of WEB's Sieve parser/generator/tests a
   - What RN does: `getDocumentAsync({ multiple: false })` (`src/screens/FilesScreen.tsx:357-360`); uploading the same name twice creates two nodes with the same name.
   - Fix hint: `multiple: true` + sequential upload loop; reuse WEB's `getUniqueName` against `visibleFiles`.
 
-- [x] **No in-app preview (image/text/markdown/PDF/audio/video/eml)** — `P2` — `missing` — done in 409cdb1 (images, text and source files, `.eml`, and PDFs on iOS open in the reader's preview; PDFs on Android, audio, video, HTML and Markdown still go to another app)
+- [x] **No in-app preview (image/text/markdown/PDF/audio/video/eml)** — `P2` — `missing` — done in 409cdb1 (images, text and source files, `.eml`, and PDFs on iOS open in the reader's preview); since 0.1.80/0.1.81 also audio, video, SVG/ICO, HTML, Markdown, PDFs on Android (native `PdfRenderer`) and ZIP listings, through the one preview the reader, list, Files and compose share (`src/components/email/use-file-preview.ts`)
   - What WEB does: `ImagePreviewModal` and `FilePreviewModal` (text, markdown, PDF incl. mobile pdf.js viewer, audio, video, EML) chosen via `getFilePreviewKind` (`lib/file-preview.ts:29-68`; `components/files/file-preview-modal.tsx`, `image-preview-modal.tsx`, `pdf-mobile-viewer.tsx`; `files-app.tsx:487-495`, `690-708`).
   - What RN does: tapping a file calls `shareAttachment` which downloads to cache and hands off to the OS share/viewer sheet (`src/screens/FilesScreen.tsx:248-258`; `src/lib/email-export.ts` "preview" variant). Works but there is no inline viewer and no "recent files" tracking.
   - Fix hint: reuse whatever attachment viewer the mail area has (image modal / WebView for text+PDF); N/A if the team decides the OS viewer is the mobile answer - then close this item.

locales/rn/ar.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "فتح في تطبيق",
       "pdf_external": "تُفتح ملفات PDF في عارض PDF على هذا الجهاز.",
-      "unsupported": "لا توجد معاينة لهذا النوع من الملفات."
+      "unsupported": "لا توجد معاينة لهذا النوع من الملفات.",
+      "media_unsupported": "لا يمكن تشغيل هذا الملف هنا.",
+      "pdf_protected": "ملف PDF هذا محمي بكلمة مرور. افتحه في تطبيق آخر لإدخال كلمة المرور.",
+      "pdf_unreadable": "لا يمكن عرض ملف PDF هذا هنا.",
+      "archive_files": "{count, plural, zero {لا ملفات} one {ملف واحد} two {ملفان} few {# ملفات} many {# ملفًا} other {# ملف}}",
+      "archive_first_files": "أول {count} ملف",
+      "archive_protected": "هذا الأرشيف محمي بكلمة مرور. افتحه في تطبيق آخر لإدخال كلمة المرور.",
+      "archive_unreadable": "لا يمكن فتح هذا الأرشيف هنا."
     },
     "received_via": "إلى {name}",
     "remove_color": "إزالة الوسم",

locales/rn/ca.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Obre en una aplicació",
       "pdf_external": "Els PDF s'obren amb el visualitzador de PDF d'aquest dispositiu.",
-      "unsupported": "No hi ha previsualització per a aquest tipus de fitxer."
+      "unsupported": "No hi ha previsualització per a aquest tipus de fitxer.",
+      "media_unsupported": "Aquest fitxer no es pot reproduir aquí.",
+      "pdf_protected": "Aquest PDF està protegit amb contrasenya. Obre'l en una altra aplicació per introduir-la.",
+      "pdf_unreadable": "Aquest PDF no es pot mostrar aquí.",
+      "archive_files": "{count, plural, one {# fitxer} other {# fitxers}}",
+      "archive_first_files": "Els primers {count} fitxers",
+      "archive_protected": "Aquest arxiu està protegit amb contrasenya. Obre'l en una altra aplicació per introduir-la.",
+      "archive_unreadable": "Aquest arxiu no es pot obrir aquí."
     },
     "received_via": "per a {name}",
     "remove_color": "Elimina l'etiqueta",

locales/rn/cs.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Otevřít v aplikaci",
       "pdf_external": "Soubory PDF se otevírají v prohlížeči PDF na tomto zařízení.",
-      "unsupported": "Pro tento typ souboru není náhled k dispozici."
+      "unsupported": "Pro tento typ souboru není náhled k dispozici.",
+      "media_unsupported": "Tento soubor zde nelze přehrát.",
+      "pdf_protected": "Toto PDF je chráněné heslem. Otevřete ho v jiné aplikaci a zadejte heslo.",
+      "pdf_unreadable": "Toto PDF zde nelze zobrazit.",
+      "archive_files": "{count, plural, one {# soubor} few {# soubory} many {# souboru} other {# souborů}}",
+      "archive_first_files": "Prvních {count} souborů",
+      "archive_protected": "Tento archiv je chráněný heslem. Otevřete ho v jiné aplikaci a zadejte heslo.",
+      "archive_unreadable": "Tento archiv zde nelze otevřít."
     },
     "received_via": "pro {name}",
     "remove_color": "Odebrat štítek",

locales/rn/da.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Åbn i app",
       "pdf_external": "PDF'er åbnes i din PDF-fremviser på denne enhed.",
-      "unsupported": "Ingen forhåndsvisning for denne filtype."
+      "unsupported": "Ingen forhåndsvisning for denne filtype.",
+      "media_unsupported": "Denne fil kan ikke afspilles her.",
+      "pdf_protected": "Denne PDF er beskyttet med adgangskode. Åbn den i en anden app for at indtaste adgangskoden.",
+      "pdf_unreadable": "Denne PDF kan ikke vises her.",
+      "archive_files": "{count, plural, one {# fil} other {# filer}}",
+      "archive_first_files": "De første {count} filer",
+      "archive_protected": "Dette arkiv er beskyttet med adgangskode. Åbn det i en anden app for at indtaste adgangskoden.",
+      "archive_unreadable": "Dette arkiv kan ikke åbnes her."
     },
     "received_via": "til {name}",
     "remove_color": "Fjern tag",

locales/rn/de.json

@@ -413,7 +413,14 @@
     "preview": {
       "open_external": "In App öffnen",
       "pdf_external": "PDFs werden in Ihrem PDF-Viewer auf diesem Gerät geöffnet.",
-      "unsupported": "Keine Vorschau für diesen Dateityp."
+      "unsupported": "Keine Vorschau für diesen Dateityp.",
+      "media_unsupported": "Diese Datei kann hier nicht abgespielt werden.",
+      "pdf_protected": "Diese PDF ist passwortgeschützt. Öffne sie in einer anderen App, um das Passwort einzugeben.",
+      "pdf_unreadable": "Diese PDF kann hier nicht angezeigt werden.",
+      "archive_files": "{count, plural, one {# Datei} other {# Dateien}}",
+      "archive_first_files": "Die ersten {count} Dateien",
+      "archive_protected": "Dieses Archiv ist passwortgeschützt. Öffne es in einer anderen App, um das Passwort einzugeben.",
+      "archive_unreadable": "Dieses Archiv kann hier nicht geöffnet werden."
     },
     "received_via": "an {name}",
     "remove_color": "Label entfernen",

locales/rn/en.json

@@ -424,7 +424,14 @@
     "preview": {
       "open_external": "Open in app",
       "pdf_external": "PDFs open in your PDF viewer on this device.",
-      "unsupported": "No preview for this file type."
+      "unsupported": "No preview for this file type.",
+      "media_unsupported": "This file can't be played here.",
+      "pdf_protected": "This PDF is password-protected. Open it in another app to enter the password.",
+      "pdf_unreadable": "This PDF can't be shown here.",
+      "archive_files": "{count, plural, one {# file} other {# files}}",
+      "archive_first_files": "The first {count} files",
+      "archive_protected": "This archive is password-protected. Open it in another app to enter the password.",
+      "archive_unreadable": "This archive can't be opened here."
     },
     "received_via": "to {name}",
     "remove_color": "Remove tag",

locales/rn/es.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Abrir en una app",
       "pdf_external": "Los PDF se abren en el visor de PDF de este dispositivo.",
-      "unsupported": "No hay vista previa para este tipo de archivo."
+      "unsupported": "No hay vista previa para este tipo de archivo.",
+      "media_unsupported": "Este archivo no se puede reproducir aquí.",
+      "pdf_protected": "Este PDF está protegido con contraseña. Ábrelo en otra aplicación para introducirla.",
+      "pdf_unreadable": "Este PDF no se puede mostrar aquí.",
+      "archive_files": "{count, plural, one {# archivo} other {# archivos}}",
+      "archive_first_files": "Los primeros {count} archivos",
+      "archive_protected": "Este archivo comprimido está protegido con contraseña. Ábrelo en otra aplicación para introducirla.",
+      "archive_unreadable": "Este archivo comprimido no se puede abrir aquí."
     },
     "received_via": "para {name}",
     "remove_color": "Eliminar etiqueta",

locales/rn/fa.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "باز کردن در برنامه",
       "pdf_external": "فایل‌های PDF در نمایشگر PDF این دستگاه باز می‌شوند.",
-      "unsupported": "برای این نوع فایل پیش‌نمایشی وجود ندارد."
+      "unsupported": "برای این نوع فایل پیش‌نمایشی وجود ندارد.",
+      "media_unsupported": "این فایل اینجا پخش نمی‌شود.",
+      "pdf_protected": "این PDF با رمز عبور محافظت شده است. برای وارد کردن رمز، آن را در برنامهٔ دیگری باز کنید.",
+      "pdf_unreadable": "این PDF اینجا نمایش داده نمی‌شود.",
+      "archive_files": "{count, plural, one {# فایل} other {# فایل}}",
+      "archive_first_files": "{count} فایل نخست",
+      "archive_protected": "این بایگانی با رمز عبور محافظت شده است. برای وارد کردن رمز، آن را در برنامهٔ دیگری باز کنید.",
+      "archive_unreadable": "این بایگانی اینجا باز نمی‌شود."
     },
     "received_via": "به {name}",
     "remove_color": "حذف برچسب",

locales/rn/fr.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Ouvrir dans une app",
       "pdf_external": "Les PDF s'ouvrent dans votre lecteur PDF sur cet appareil.",
-      "unsupported": "Aucun aperçu pour ce type de fichier."
+      "unsupported": "Aucun aperçu pour ce type de fichier.",
+      "media_unsupported": "Ce fichier ne peut pas être lu ici.",
+      "pdf_protected": "Ce PDF est protégé par un mot de passe. Ouvrez-le dans une autre application pour le saisir.",
+      "pdf_unreadable": "Ce PDF ne peut pas être affiché ici.",
+      "archive_files": "{count, plural, one {# fichier} other {# fichiers}}",
+      "archive_first_files": "Les {count} premiers fichiers",
+      "archive_protected": "Cette archive est protégée par un mot de passe. Ouvrez-la dans une autre application pour le saisir.",
+      "archive_unreadable": "Cette archive ne peut pas être ouverte ici."
     },
     "received_via": "à {name}",
     "remove_color": "Retirer l'étiquette",

locales/rn/he.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "פתח באפליקציה",
       "pdf_external": "קובצי PDF נפתחים במציג ה-PDF במכשיר זה.",
-      "unsupported": "אין תצוגה מקדימה לסוג קובץ זה."
+      "unsupported": "אין תצוגה מקדימה לסוג קובץ זה.",
+      "media_unsupported": "לא ניתן להפעיל את הקובץ הזה כאן.",
+      "pdf_protected": "קובץ ה-PDF הזה מוגן בסיסמה. פתחו אותו באפליקציה אחרת כדי להזין את הסיסמה.",
+      "pdf_unreadable": "לא ניתן להציג את קובץ ה-PDF הזה כאן.",
+      "archive_files": "{count, plural, one {קובץ אחד} two {שני קבצים} other {# קבצים}}",
+      "archive_first_files": "{count} הקבצים הראשונים",
+      "archive_protected": "הארכיון הזה מוגן בסיסמה. פתחו אותו באפליקציה אחרת כדי להזין את הסיסמה.",
+      "archive_unreadable": "לא ניתן לפתוח את הארכיון הזה כאן."
     },
     "received_via": "אל {name}",
     "remove_color": "הסר תג",

locales/rn/hu.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Megnyitás alkalmazásban",
       "pdf_external": "A PDF-fájlok az eszköz PDF-megjelenítőjében nyílnak meg.",
-      "unsupported": "Ehhez a fájltípushoz nincs előnézet."
+      "unsupported": "Ehhez a fájltípushoz nincs előnézet.",
+      "media_unsupported": "Ez a fájl itt nem játszható le.",
+      "pdf_protected": "Ez a PDF jelszóval védett. Nyisd meg egy másik alkalmazásban a jelszó megadásához.",
+      "pdf_unreadable": "Ez a PDF itt nem jeleníthető meg.",
+      "archive_files": "{count, plural, one {# fájl} other {# fájl}}",
+      "archive_first_files": "Az első {count} fájl",
+      "archive_protected": "Ez az archívum jelszóval védett. Nyisd meg egy másik alkalmazásban a jelszó megadásához.",
+      "archive_unreadable": "Ez az archívum itt nem nyitható meg."
     },
     "received_via": "címzett: {name}",
     "remove_color": "Címke eltávolítása",

locales/rn/it.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Apri in un'app",
       "pdf_external": "I PDF si aprono nel lettore PDF di questo dispositivo.",
-      "unsupported": "Nessuna anteprima per questo tipo di file."
+      "unsupported": "Nessuna anteprima per questo tipo di file.",
+      "media_unsupported": "Questo file non può essere riprodotto qui.",
+      "pdf_protected": "Questo PDF è protetto da password. Aprilo in un'altra app per inserirla.",
+      "pdf_unreadable": "Questo PDF non può essere visualizzato qui.",
+      "archive_files": "{count, plural, one {# file} other {# file}}",
+      "archive_first_files": "I primi {count} file",
+      "archive_protected": "Questo archivio è protetto da password. Aprilo in un'altra app per inserirla.",
+      "archive_unreadable": "Questo archivio non può essere aperto qui."
     },
     "received_via": "a {name}",
     "remove_color": "Rimuovi etichetta",

locales/rn/ja.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "アプリで開く",
       "pdf_external": "PDF はこのデバイスの PDF ビューアーで開きます。",
-      "unsupported": "このファイル形式はプレビューできません。"
+      "unsupported": "このファイル形式はプレビューできません。",
+      "media_unsupported": "このファイルはここでは再生できません。",
+      "pdf_protected": "このPDFはパスワードで保護されています。パスワードを入力するには別のアプリで開いてください。",
+      "pdf_unreadable": "このPDFはここでは表示できません。",
+      "archive_files": "{count, plural, other {# 個のファイル}}",
+      "archive_first_files": "最初の {count} 個のファイル",
+      "archive_protected": "このアーカイブはパスワードで保護されています。パスワードを入力するには別のアプリで開いてください。",
+      "archive_unreadable": "このアーカイブはここでは開けません。"
     },
     "received_via": "{name}宛",
     "remove_color": "ラベルを削除",

locales/rn/ko.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "앱에서 열기",
       "pdf_external": "PDF는 이 기기의 PDF 뷰어에서 열려요.",
-      "unsupported": "이 파일 형식은 미리보기를 지원하지 않아요."
+      "unsupported": "이 파일 형식은 미리보기를 지원하지 않아요.",
+      "media_unsupported": "이 파일은 여기서 재생할 수 없습니다.",
+      "pdf_protected": "이 PDF는 암호로 보호되어 있습니다. 암호를 입력하려면 다른 앱에서 여세요.",
+      "pdf_unreadable": "이 PDF는 여기서 표시할 수 없습니다.",
+      "archive_files": "{count, plural, other {파일 #개}}",
+      "archive_first_files": "처음 {count}개 파일",
+      "archive_protected": "이 압축 파일은 암호로 보호되어 있습니다. 암호를 입력하려면 다른 앱에서 여세요.",
+      "archive_unreadable": "이 압축 파일은 여기서 열 수 없습니다."
     },
     "received_via": "받는 사람: {name}",
     "remove_color": "태그 제거",

locales/rn/lv.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Atvērt lietotnē",
       "pdf_external": "PDF faili tiek atvērti šīs ierīces PDF skatītājā.",
-      "unsupported": "Šim faila tipam nav priekšskatījuma."
+      "unsupported": "Šim faila tipam nav priekšskatījuma.",
+      "media_unsupported": "Šo failu šeit nevar atskaņot.",
+      "pdf_protected": "Šis PDF ir aizsargāts ar paroli. Atveriet to citā lietotnē, lai ievadītu paroli.",
+      "pdf_unreadable": "Šo PDF šeit nevar parādīt.",
+      "archive_files": "{count, plural, zero {# failu} one {# fails} other {# faili}}",
+      "archive_first_files": "Pirmie {count} faili",
+      "archive_protected": "Šis arhīvs ir aizsargāts ar paroli. Atveriet to citā lietotnē, lai ievadītu paroli.",
+      "archive_unreadable": "Šo arhīvu šeit nevar atvērt."
     },
     "received_via": "kam: {name}",
     "remove_color": "Noņemt tagu",

locales/rn/mn.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Апп-д нээх",
       "pdf_external": "PDF файлууд энэ төхөөрөмжийн PDF үзэгчид нээгдэнэ.",
-      "unsupported": "Энэ төрлийн файлыг урьдчилан харах боломжгүй."
+      "unsupported": "Энэ төрлийн файлыг урьдчилан харах боломжгүй.",
+      "media_unsupported": "Энэ файлыг энд тоглуулах боломжгүй.",
+      "pdf_protected": "Энэ PDF нууц үгээр хамгаалагдсан. Нууц үг оруулахын тулд өөр апп-аар нээнэ үү.",
+      "pdf_unreadable": "Энэ PDF-ийг энд харуулах боломжгүй.",
+      "archive_files": "{count, plural, one {# файл} other {# файл}}",
+      "archive_first_files": "Эхний {count} файл",
+      "archive_protected": "Энэ архив нууц үгээр хамгаалагдсан. Нууц үг оруулахын тулд өөр апп-аар нээнэ үү.",
+      "archive_unreadable": "Энэ архивыг энд нээх боломжгүй."
     },
     "received_via": "Хэнд: {name}",
     "remove_color": "Тагийг хасах",

locales/rn/nb.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Åpne i app",
       "pdf_external": "PDF-filer åpnes i PDF-leseren på denne enheten.",
-      "unsupported": "Ingen forhåndsvisning for denne filtypen."
+      "unsupported": "Ingen forhåndsvisning for denne filtypen.",
+      "media_unsupported": "Denne filen kan ikke spilles av her.",
+      "pdf_protected": "Denne PDF-en er passordbeskyttet. Åpne den i en annen app for å skrive inn passordet.",
+      "pdf_unreadable": "Denne PDF-en kan ikke vises her.",
+      "archive_files": "{count, plural, one {# fil} other {# filer}}",
+      "archive_first_files": "De første {count} filene",
+      "archive_protected": "Dette arkivet er passordbeskyttet. Åpne det i en annen app for å skrive inn passordet.",
+      "archive_unreadable": "Dette arkivet kan ikke åpnes her."
     },
     "received_via": "til {name}",
     "remove_color": "Fjern etiketten",

locales/rn/nl.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Openen in app",
       "pdf_external": "PDF's worden geopend in de PDF-viewer op dit apparaat.",
-      "unsupported": "Geen voorbeeld voor dit bestandstype."
+      "unsupported": "Geen voorbeeld voor dit bestandstype.",
+      "media_unsupported": "Dit bestand kan hier niet worden afgespeeld.",
+      "pdf_protected": "Deze pdf is beveiligd met een wachtwoord. Open hem in een andere app om het wachtwoord in te voeren.",
+      "pdf_unreadable": "Deze pdf kan hier niet worden weergegeven.",
+      "archive_files": "{count, plural, one {# bestand} other {# bestanden}}",
+      "archive_first_files": "De eerste {count} bestanden",
+      "archive_protected": "Dit archief is beveiligd met een wachtwoord. Open het in een andere app om het wachtwoord in te voeren.",
+      "archive_unreadable": "Dit archief kan hier niet worden geopend."
     },
     "received_via": "aan {name}",
     "remove_color": "Label verwijderen",

locales/rn/pl.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Otwórz w aplikacji",
       "pdf_external": "Pliki PDF otwierają się w przeglądarce PDF na tym urządzeniu.",
-      "unsupported": "Brak podglądu dla tego typu pliku."
+      "unsupported": "Brak podglądu dla tego typu pliku.",
+      "media_unsupported": "Tego pliku nie można tutaj odtworzyć.",
+      "pdf_protected": "Ten plik PDF jest chroniony hasłem. Otwórz go w innej aplikacji, aby wpisać hasło.",
+      "pdf_unreadable": "Tego pliku PDF nie można tutaj wyświetlić.",
+      "archive_files": "{count, plural, one {# plik} few {# pliki} many {# plików} other {# pliku}}",
+      "archive_first_files": "Pierwsze {count} plików",
+      "archive_protected": "To archiwum jest chronione hasłem. Otwórz je w innej aplikacji, aby wpisać hasło.",
+      "archive_unreadable": "Tego archiwum nie można tutaj otworzyć."
     },
     "received_via": "do {name}",
     "remove_color": "Usuń etykietę",

locales/rn/pt.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Abrir em outro app",
       "pdf_external": "PDFs são abertos no leitor de PDF deste dispositivo.",
-      "unsupported": "Sem pré-visualização para este tipo de arquivo."
+      "unsupported": "Sem pré-visualização para este tipo de arquivo.",
+      "media_unsupported": "Este ficheiro não pode ser reproduzido aqui.",
+      "pdf_protected": "Este PDF está protegido por palavra-passe. Abra-o noutra aplicação para a introduzir.",
+      "pdf_unreadable": "Este PDF não pode ser mostrado aqui.",
+      "archive_files": "{count, plural, one {# ficheiro} other {# ficheiros}}",
+      "archive_first_files": "Os primeiros {count} ficheiros",
+      "archive_protected": "Este arquivo está protegido por palavra-passe. Abra-o noutra aplicação para a introduzir.",
+      "archive_unreadable": "Este arquivo não pode ser aberto aqui."
     },
     "received_via": "para {name}",
     "remove_color": "Remover etiqueta",

locales/rn/ro.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Deschideți într-o aplicație",
       "pdf_external": "Fișierele PDF se deschid în vizualizatorul PDF de pe acest dispozitiv.",
-      "unsupported": "Nu există previzualizare pentru acest tip de fișier."
+      "unsupported": "Nu există previzualizare pentru acest tip de fișier.",
+      "media_unsupported": "Acest fișier nu poate fi redat aici.",
+      "pdf_protected": "Acest PDF este protejat cu parolă. Deschide-l în altă aplicație pentru a introduce parola.",
+      "pdf_unreadable": "Acest PDF nu poate fi afișat aici.",
+      "archive_files": "{count, plural, one {# fișier} few {# fișiere} other {# de fișiere}}",
+      "archive_first_files": "Primele {count} fișiere",
+      "archive_protected": "Această arhivă este protejată cu parolă. Deschide-o în altă aplicație pentru a introduce parola.",
+      "archive_unreadable": "Această arhivă nu poate fi deschisă aici."
     },
     "received_via": "către {name}",
     "remove_color": "Eliminați eticheta",

locales/rn/ru.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Открыть в приложении",
       "pdf_external": "PDF-файлы открываются в программе просмотра PDF на этом устройстве.",
-      "unsupported": "Для этого типа файлов нет предпросмотра."
+      "unsupported": "Для этого типа файлов нет предпросмотра.",
+      "media_unsupported": "Этот файл нельзя воспроизвести здесь.",
+      "pdf_protected": "Этот PDF защищён паролем. Откройте его в другом приложении, чтобы ввести пароль.",
+      "pdf_unreadable": "Этот PDF нельзя показать здесь.",
+      "archive_files": "{count, plural, one {# файл} few {# файла} many {# файлов} other {# файла}}",
+      "archive_first_files": "Первые {count} файлов",
+      "archive_protected": "Этот архив защищён паролем. Откройте его в другом приложении, чтобы ввести пароль.",
+      "archive_unreadable": "Этот архив нельзя открыть здесь."
     },
     "received_via": "на {name}",
     "remove_color": "Убрать тег",

locales/rn/sk.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Otvoriť v aplikácii",
       "pdf_external": "Súbory PDF sa otvárajú v prehliadači PDF na tomto zariadení.",
-      "unsupported": "Pre tento typ súboru nie je k dispozícii náhľad."
+      "unsupported": "Pre tento typ súboru nie je k dispozícii náhľad.",
+      "media_unsupported": "Tento súbor tu nie je možné prehrať.",
+      "pdf_protected": "Toto PDF je chránené heslom. Otvorte ho v inej aplikácii a zadajte heslo.",
+      "pdf_unreadable": "Toto PDF tu nie je možné zobraziť.",
+      "archive_files": "{count, plural, one {# súbor} few {# súbory} many {# súboru} other {# súborov}}",
+      "archive_first_files": "Prvých {count} súborov",
+      "archive_protected": "Tento archív je chránený heslom. Otvorte ho v inej aplikácii a zadajte heslo.",
+      "archive_unreadable": "Tento archív tu nie je možné otvoriť."
     },
     "received_via": "pre {name}",
     "remove_color": "Odstrániť štítok",

locales/rn/tr.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Uygulamada aç",
       "pdf_external": "PDF dosyaları bu cihazdaki PDF görüntüleyicide açılır.",
-      "unsupported": "Bu dosya türü için önizleme yok."
+      "unsupported": "Bu dosya türü için önizleme yok.",
+      "media_unsupported": "Bu dosya burada oynatılamıyor.",
+      "pdf_protected": "Bu PDF parola korumalı. Parolayı girmek için başka bir uygulamada açın.",
+      "pdf_unreadable": "Bu PDF burada gösterilemiyor.",
+      "archive_files": "{count, plural, one {# dosya} other {# dosya}}",
+      "archive_first_files": "İlk {count} dosya",
+      "archive_protected": "Bu arşiv parola korumalı. Parolayı girmek için başka bir uygulamada açın.",
+      "archive_unreadable": "Bu arşiv burada açılamıyor."
     },
     "received_via": "alıcı: {name}",
     "remove_color": "Etiketi kaldır",

locales/rn/uk.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "Відкрити в застосунку",
       "pdf_external": "PDF-файли відкриваються в переглядачі PDF на цьому пристрої.",
-      "unsupported": "Для цього типу файлів немає попереднього перегляду."
+      "unsupported": "Для цього типу файлів немає попереднього перегляду.",
+      "media_unsupported": "Цей файл не можна відтворити тут.",
+      "pdf_protected": "Цей PDF захищено паролем. Відкрийте його в іншому застосунку, щоб ввести пароль.",
+      "pdf_unreadable": "Цей PDF не можна показати тут.",
+      "archive_files": "{count, plural, one {# файл} few {# файли} many {# файлів} other {# файлу}}",
+      "archive_first_files": "Перші {count} файлів",
+      "archive_protected": "Цей архів захищено паролем. Відкрийте його в іншому застосунку, щоб ввести пароль.",
+      "archive_unreadable": "Цей архів не можна відкрити тут."
     },
     "received_via": "на {name}",
     "remove_color": "Прибрати тег",

locales/rn/zh-TW.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "在應用程式中開啟",
       "pdf_external": "PDF 會在此裝置的 PDF 檢視器中開啟。",
-      "unsupported": "無法預覽此檔案類型。"
+      "unsupported": "無法預覽此檔案類型。",
+      "media_unsupported": "無法在此播放這個檔案。",
+      "pdf_protected": "此 PDF 受密碼保護。請在其他應用程式中開啟以輸入密碼。",
+      "pdf_unreadable": "無法在此顯示這個 PDF。",
+      "archive_files": "{count, plural, other {# 個檔案}}",
+      "archive_first_files": "前 {count} 個檔案",
+      "archive_protected": "此壓縮檔受密碼保護。請在其他應用程式中開啟以輸入密碼。",
+      "archive_unreadable": "無法在此開啟這個壓縮檔。"
     },
     "received_via": "寄給 {name}",
     "remove_color": "移除標籤",

locales/rn/zh.json

@@ -407,7 +407,14 @@
     "preview": {
       "open_external": "在应用中打开",
       "pdf_external": "PDF 将在此设备的 PDF 查看器中打开。",
-      "unsupported": "无法预览此类文件。"
+      "unsupported": "无法预览此类文件。",
+      "media_unsupported": "无法在此播放该文件。",
+      "pdf_protected": "此 PDF 受密码保护。请在其他应用中打开以输入密码。",
+      "pdf_unreadable": "无法在此显示该 PDF。",
+      "archive_files": "{count, plural, other {# 个文件}}",
+      "archive_first_files": "前 {count} 个文件",
+      "archive_protected": "此压缩包受密码保护。请在其他应用中打开以输入密码。",
+      "archive_unreadable": "无法在此打开该压缩包。"
     },
     "received_via": "发给 {name}",
     "remove_color": "删除标签",

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "bulwark-mobile",
-  "version": "0.1.79",
+  "version": "0.1.82",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "bulwark-mobile",
-      "version": "0.1.79",
+      "version": "0.1.82",
       "hasInstallScript": true,
       "license": "AGPL-3.0-only",
       "dependencies": {

package.json

@@ -1,6 +1,6 @@
 {
   "name": "bulwark-mobile",
-  "version": "0.1.79",
+  "version": "0.1.82",
   "license": "AGPL-3.0-only",
   "main": "index.ts",
   "scripts": {

src/components/email/AttachmentPreviewModal.tsx

@@ -1,29 +1,44 @@
 import React from 'react';
 import {
-  View, Text, StyleSheet, Modal, Pressable, ScrollView, Image, ActivityIndicator, Platform, useWindowDimensions,
+  View, Text, StyleSheet, Modal, Pressable, ScrollView, Image, ActivityIndicator, Platform, PixelRatio, Alert,
+  useWindowDimensions,
 } from 'react-native';
 import { SafeAreaView } from 'react-native-safe-area-context';
-import { WebView } from 'react-native-webview';
+import { WebView, type WebViewMessageEvent } from 'react-native-webview';
 import { X, ExternalLink, Share2, Download } from '../icons';
 import type { Email } from '../../api/types';
 import { spacing, radius, typography, componentSizes, type ThemePalette } from '../../theme/tokens';
 import { useColors } from '../../theme/colors';
 import { useLocaleStore } from '../../stores/locale-store';
+import { useSettingsStore } from '../../stores/settings-store';
 import EmailBodyView from '../EmailBodyView';
-import type { PreviewKind } from '../../lib/attachment-display';
+import {
+  handoffMimeType, needsNativeImageDecoder, needsWebImageViewer, type PreviewKind,
+} from '../../lib/file-preview';
+import { pdfPageFileName, renderPdfPage } from '../../lib/pdf-pages';
+import type { ZipArchive } from '../../lib/zip-preview';
+import { formatFullDateTime } from '../../lib/email-date';
 import type { EmlPreview } from './use-body-override';
+import { useFilePreview } from './use-file-preview';
+import { ArchiveSummary, PreviewPartList, type PreviewPart } from './PreviewPartList';
 import { MODAL_ORIENTATIONS } from '../../lib/modal-orientations';
 
 export interface PreviewItem {
   kind: PreviewKind;
   name: string;
   mimeType: string;
-  /** Local file:// URI for images and PDFs. */
+  /** Local file:// URI of the downloaded copy (images, PDFs, media). */
   fileUri?: string;
+  /** The viewer page next to the file (images, video, audio, Android's PDFs); see preview-viewer-html. */
+  viewerUri?: string;
   /** Decoded text for text-like parts. */
   text?: string;
+  /** The document for HTML and Markdown files, shown through the mail sanitiser. */
+  html?: string;
   /** Parsed embedded message for .eml previews. */
   eml?: EmlPreview;
+  /** A ZIP's directory, for archive previews. */
+  archive?: ZipArchive;
   /** Replaces "No preview for this file type." on the fallback screen (e.g. the file is too large). */
   notice?: string;
 }
@@ -34,7 +49,7 @@ interface Props {
   /** Header title while the item is still loading. */
   title?: string;
   onClose: () => void;
-  /** Hand the file to an external app (PDF on Android, unsupported types, the header's Open button). */
+  /** Hand the file to another app (types without a preview, the header's Open button). */
   onOpenExternal: () => void;
   onShare: () => void;
   /** Save a copy; adds a Download button to the header. */
@@ -43,11 +58,93 @@ interface Props {
   docked?: boolean;
 }
 
+interface ViewerWebViewProps {
+  uri: string;
+  background: string;
+  onFailed: () => void;
+  /** Messages other than 'error'. */
+  onMessage?: (data: string) => void;
+  webRef?: React.Ref<WebView>;
+}
+
 /**
- * In-app preview for images, PDFs (iOS renders them in the WebView; Android
- * has no built-in PDF renderer, so it offers the external viewer), text and
- * embedded messages. Anything else goes to the external viewer / share sheet.
- * Used by the reader's attachment chips and the Files tab.
+ * A local page in a WebView that may read only its own folder: the image,
+ * media and PDF viewers. It posts 'error' when the file doesn't decode.
+ */
+function ViewerWebView({ uri, background, onFailed, onMessage, webRef }: ViewerWebViewProps) {
+  const folder = uri.slice(0, uri.lastIndexOf('/') + 1);
+  const handleMessage = (e: WebViewMessageEvent) => {
+    if (e.nativeEvent.data === 'error') onFailed();
+    else onMessage?.(e.nativeEvent.data);
+  };
+  return (
+    <WebView
+      ref={webRef}
+      source={{ uri }}
+      originWhitelist={['file://*']}
+      allowFileAccess
+      allowingReadAccessToURL={folder}
+      javaScriptEnabled
+      domStorageEnabled={false}
+      cacheEnabled={false}
+      incognito
+      allowsInlineMediaPlayback
+      mediaPlaybackRequiresUserAction={false}
+      allowsFullscreenVideo
+      allowsPictureInPictureMediaPlayback
+      allowsAirPlayForMediaPlayback
+      setSupportMultipleWindows={false}
+      setBuiltInZoomControls
+      setDisplayZoomControls={false}
+      overScrollMode="never"
+      bounces={false}
+      onShouldStartLoadWithRequest={(req) => req.url === uri}
+      onMessage={handleMessage}
+      onError={onFailed}
+      style={[viewerStyles.fill, { backgroundColor: background }]}
+      containerStyle={{ backgroundColor: background }}
+    />
+  );
+}
+
+// Pages are rendered half again as wide as the screen's pixels, so text stays
+// sharp at the first zoom step; PdfRenderer's bitmap is capped natively.
+const PDF_PAGE_OVERSAMPLE = 1.5;
+
+/**
+ * Android's PDF view: the viewer page asks for each page as it comes near
+ * the screen, and the page is rendered next to it by the platform's
+ * PdfRenderer (pdf-pages.ts).
+ */
+function PdfPagesView({ fileUri, viewerUri, background, onFailed }: {
+  fileUri: string;
+  viewerUri: string;
+  background: string;
+  onFailed: () => void;
+}) {
+  const ref = React.useRef<WebView>(null);
+  const { width } = useWindowDimensions();
+  const pagePx = PixelRatio.getPixelSizeForLayoutSize(Math.min(width, 1000)) * PDF_PAGE_OVERSAMPLE;
+  const folder = viewerUri.slice(0, viewerUri.lastIndexOf('/') + 1);
+  const onMessage = (data: string) => {
+    const m = /^page:(\d+)$/.exec(data);
+    if (!m) return;
+    const index = Number(m[1]);
+    const name = pdfPageFileName(index);
+    renderPdfPage(fileUri, index, pagePx, folder + name)
+      .then(() => ref.current?.injectJavaScript(`window.__pdfPage(${index}, ${JSON.stringify(name)});true;`))
+      .catch(() => undefined);
+  };
+  return <ViewerWebView webRef={ref} uri={viewerUri} background={background} onFailed={onFailed} onMessage={onMessage} />;
+}
+
+/**
+ * In-app preview for images, PDFs (iOS's WebView shows them, Android renders the pages), video
+ * and audio (the WebView's player), text, Markdown and HTML documents,
+ * embedded messages and ZIP archives. The files inside an archive or a
+ * message open in a preview of their own on top. Files that don't decode,
+ * and types without a preview, offer another app instead. Used by every
+ * place that opens a file.
  */
 export function AttachmentPreviewModal({
   item, loading, title, onClose, onOpenExternal, onShare, onDownload, docked = false,
@@ -55,32 +152,88 @@ export function AttachmentPreviewModal({
   const c = useColors();
   const styles = React.useMemo(() => makeStyles(c), [c]);
   const t = useLocaleStore((s) => s.t);
+  const locale = useLocaleStore((s) => s.locale);
+  const timeFormat = useSettingsStore((s) => s.timeFormat);
   const { width } = useWindowDimensions();
-  // An image the platform can't decode would stay blank; fall back to the
-  // external viewer instead. Keyed by URI so the next item starts clean.
-  const [failedImageUri, setFailedImageUri] = React.useState<string | null>(null);
+  // Files inside this one (archive entries, an .eml's attachments).
+  const nested = useFilePreview();
+  const { open: openNested } = nested;
+  const openPart = React.useCallback(async (part: PreviewPart) => {
+    try {
+      const bytes = await part.read();
+      await openNested({
+        from: 'bytes',
+        bytes,
+        name: part.name,
+        type: part.type || handoffMimeType(part.name, ''),
+        size: bytes.byteLength,
+      });
+    } catch (e) {
+      Alert.alert(t('email_viewer.attachment_failed', 'Could not open attachment'), e instanceof Error ? e.message : String(e));
+    }
+  }, [openNested, t]);
+  const archive = item?.kind === 'archive' ? item.archive : undefined;
+  const archiveParts = React.useMemo<PreviewPart[]>(() => {
+    if (!archive) return [];
+    return archive.entries.map((entry) => ({
+      key: entry.path,
+      name: entry.name,
+      folder: entry.folder,
+      size: entry.size,
+      read: () => archive.read(entry.path),
+    }));
+  }, [archive]);
+  const emlAttachments = item?.kind === 'eml' ? item.eml?.attachments : undefined;
+  const emlParts = React.useMemo<PreviewPart[]>(() => (emlAttachments ?? []).map((att, i) => ({
+    key: `${i}-${att.name}`,
+    name: att.name,
+    type: att.type,
+    size: att.size,
+    read: async () => att.bytes,
+  })), [emlAttachments]);
+  // Which viewers failed for the open file, keyed by its URI so the next one
+  // starts clean: React Native's Image falls back to the WebView viewer, and
+  // a WebView that can't decode the file falls back to another app.
+  const [failed, setFailed] = React.useState<{ uri: string; native?: boolean; web?: boolean } | null>(null);
+  const markFailed = React.useCallback((uri: string | undefined, which: 'native' | 'web') => {
+    if (!uri) return;
+    setFailed((prev) => ({ ...(prev?.uri === uri ? prev : {}), uri, [which]: true }));
+  }, []);
   // The image fits the area it is shown in (a pane, a landscape window),
   // not a box derived from the window width that ran past the screen.
   const [imageArea, setImageArea] = React.useState<{ width: number; height: number } | null>(null);
 
-  const emlEmail = React.useMemo<Email | null>(() => {
-    if (!item?.eml) return null;
+  const docEmail = React.useMemo<Email | null>(() => {
+    if (!item || (!item.eml && item.html == null)) return null;
     return {
-      id: `eml-preview-${item.name}`,
+      id: `file-preview-${item.kind}-${item.fileUri ?? item.name}`,
       threadId: '',
       mailboxIds: {},
       keywords: {},
       size: 0,
-      receivedAt: item.eml.date ?? new Date().toISOString(),
+      receivedAt: item.eml?.date ?? new Date().toISOString(),
       hasAttachment: false,
-      subject: item.eml.subject,
+      subject: item.eml?.subject ?? item.name,
     };
   }, [item]);
 
-  const imageFailed = item?.kind === 'image' && !!item.fileUri && failedImageUri === item.fileUri;
-  const pdfInline = item?.kind === 'pdf' && Platform.OS === 'ios' && !!item.fileUri;
+  const failure = item?.fileUri && failed?.uri === item.fileUri ? failed : null;
+  // Android's WebView zooms; React Native's Image there doesn't. iOS zooms
+  // the native image in its ScrollView. Each side's gaps go to the other.
+  const imageInWeb = item?.kind === 'image' && !!item.viewerUri && !failure?.web && (
+    failure?.native
+    || (Platform.OS === 'android' ? !needsNativeImageDecoder(item) : needsWebImageViewer(item))
+  );
+  const imageFailed = item?.kind === 'image' && (
+    !!failure?.web && (!!failure.native || !item.viewerUri || needsWebImageViewer(item))
+    || (!!failure?.native && !item.viewerUri)
+  );
+  const mediaFailed = (item?.kind === 'video' || item?.kind === 'audio') && !!failure?.web;
+  const pdfInline = item?.kind === 'pdf' && !!item.fileUri && (Platform.OS === 'ios' || !!item.viewerUri) && !failure?.web;
   // The fallback screen has its own Open button; the header adds one elsewhere.
-  const showsFallback = !!item && (item.kind === 'none' || (item.kind === 'pdf' && !pdfInline) || imageFailed);
+  const showsFallback = !!item && (
+    item.kind === 'none' || (item.kind === 'pdf' && !pdfInline) || imageFailed || mediaFailed
+  );
 
   const renderFallback = (message: string) => (
     <View style={styles.centered}>
@@ -92,6 +245,14 @@ export function AttachmentPreviewModal({
     </View>
   );
 
+  const renderDocument = (header?: React.ReactNode, footer?: React.ReactNode) => (
+    <ScrollView style={styles.flex}>
+      {header}
+      {docEmail && <EmailBodyView email={docEmail} bodyOverride={{ html: item?.html ?? item?.eml?.html, text: item?.eml?.text }} />}
+      {footer}
+    </ScrollView>
+  );
+
   const renderBody = () => {
     if (loading || !item) {
       return (
@@ -105,6 +266,16 @@ export function AttachmentPreviewModal({
         if (imageFailed) {
           return renderFallback(t('email_viewer.preview.unsupported', 'No preview for this file type.'));
         }
+        if (imageInWeb && item.viewerUri) {
+          return (
+            <ViewerWebView
+              key={item.viewerUri}
+              uri={item.viewerUri}
+              background={c.background}
+              onFailed={() => markFailed(item.fileUri, 'web')}
+            />
+          );
+        }
         return (
           <ScrollView
             style={styles.flex}
@@ -124,11 +295,35 @@ export function AttachmentPreviewModal({
                 : { width: width - spacing.lg * 2, height: width * 1.2 }}
               resizeMode="contain"
               accessibilityLabel={item.name}
-              onError={() => setFailedImageUri(item.fileUri ?? null)}
+              onError={() => markFailed(item.fileUri, 'native')}
             />
           </ScrollView>
         );
+      case 'video':
+      case 'audio':
+        if (mediaFailed || !item.viewerUri) {
+          return renderFallback(t('email_viewer.preview.media_unsupported', "This file can't be played here."));
+        }
+        return (
+          <ViewerWebView
+            key={item.viewerUri}
+            uri={item.viewerUri}
+            background={item.kind === 'video' ? '#000' : c.background}
+            onFailed={() => markFailed(item.fileUri, 'web')}
+          />
+        );
       case 'pdf':
+        if (pdfInline && item.fileUri && item.viewerUri) {
+          return (
+            <PdfPagesView
+              key={item.viewerUri}
+              fileUri={item.fileUri}
+              viewerUri={item.viewerUri}
+              background={c.surface}
+              onFailed={() => markFailed(item.fileUri, 'web')}
+            />
+          );
+        }
         if (pdfInline && item.fileUri) {
           return (
             <WebView
@@ -143,32 +338,45 @@ export function AttachmentPreviewModal({
             />
           );
         }
-        return renderFallback(t('email_viewer.preview.pdf_external', 'PDFs open in your PDF viewer on this device.'));
+        return renderFallback(t('email_viewer.preview.pdf_unreadable', "This PDF can't be shown here."));
       case 'text':
         return (
           <ScrollView style={styles.flex} contentContainerStyle={styles.textScroll}>
             <Text selectable style={styles.text}>{item.text ?? ''}</Text>
           </ScrollView>
         );
+      case 'html':
+      case 'markdown':
+        return renderDocument();
       case 'eml':
+        return renderDocument(
+          <View style={styles.emlHeader}>
+            <Text style={styles.emlSubject}>{item.eml?.subject || t('email_viewer.no_subject', '(No Subject)')}</Text>
+            {item.eml?.from ? <Text style={styles.emlMeta}>{item.eml.from}</Text> : null}
+            {item.eml?.date ? <Text style={styles.emlMeta}>{formatFullDateTime(item.eml.date, timeFormat, locale) || item.eml.date}</Text> : null}
+          </View>,
+          emlParts.length > 0 ? (
+            <PreviewPartList
+              inline
+              parts={emlParts}
+              onOpen={openPart}
+              header={<ArchiveSummary count={emlParts.length} truncated={false} />}
+            />
+          ) : null,
+        );
+      case 'archive':
+        if (!item.archive) break;
         return (
-          <ScrollView style={styles.flex}>
-            <View style={styles.emlHeader}>
-              <Text style={styles.emlSubject}>{item.eml?.subject || t('email_viewer.no_subject', '(No Subject)')}</Text>
-              {item.eml?.from ? <Text style={styles.emlMeta}>{item.eml.from}</Text> : null}
-              {item.eml?.date ? <Text style={styles.emlMeta}>{item.eml.date}</Text> : null}
-            </View>
-            {emlEmail && (
-              <EmailBodyView
-                email={emlEmail}
-                bodyOverride={{ html: item.eml?.html, text: item.eml?.text }}
-              />
-            )}
-          </ScrollView>
+          <PreviewPartList
+            parts={archiveParts}
+            onOpen={openPart}
+            header={<ArchiveSummary count={archiveParts.length} truncated={item.archive.truncated} />}
+          />
         );
       default:
-        return renderFallback(item.notice ?? t('email_viewer.preview.unsupported', 'No preview for this file type.'));
+        break;
     }
+    return renderFallback(item.notice ?? t('email_viewer.preview.unsupported', 'No preview for this file type.'));
   };
 
   const content = (
@@ -219,6 +427,7 @@ export function AttachmentPreviewModal({
           </Pressable>
         </View>
         {renderBody()}
+        {nested.modalProps.item || nested.modalProps.loading ? <AttachmentPreviewModal {...nested.modalProps} /> : null}
       </SafeAreaView>
   );
   if (docked) return item || loading ? content : null;
@@ -229,6 +438,8 @@ export function AttachmentPreviewModal({
   );
 }
 
+const viewerStyles = StyleSheet.create({ fill: { flex: 1 } });
+
 function makeStyles(c: ThemePalette) {
   return StyleSheet.create({
     container: { flex: 1, backgroundColor: c.background },

src/components/email/PreviewPartList.tsx

@@ -0,0 +1,152 @@
+import React from 'react';
+import { ActivityIndicator, FlatList, Pressable, StyleSheet, Text, View } from 'react-native';
+import {
+  File as FileIcon, FileArchive, FileAudio, FileImage, FileSpreadsheet, FileText, FileVideo,
+} from '../icons';
+import { formatSize } from '../../lib/attachment-display';
+import { filePreviewKind, handoffMimeType } from '../../lib/file-preview';
+import { spacing, radius, typography, type ThemePalette } from '../../theme/tokens';
+import { useColors } from '../../theme/colors';
+import { useLocaleStore } from '../../stores/locale-store';
+
+/** A file inside a file: an archive entry or an attachment of an .eml. */
+export interface PreviewPart {
+  key: string;
+  name: string;
+  /** Folder inside an archive, '' at the top. */
+  folder?: string;
+  type?: string;
+  size?: number;
+  read: () => Promise<Uint8Array>;
+}
+
+function iconFor(part: PreviewPart) {
+  const type = part.type || handoffMimeType(part.name, '');
+  if (/\.(xlsx?|ods|csv|tsv|numbers)$/i.test(part.name)) return FileSpreadsheet;
+  if (/\.(zip|7z|rar|gz|tgz|tar|bz2|xz)$/i.test(part.name)) return FileArchive;
+  // Platform-independent: the icon names the format, not what plays here.
+  switch (filePreviewKind({ name: part.name, type }, { platform: 'android' })) {
+    case 'image': return FileImage;
+    case 'video': return FileVideo;
+    case 'audio': return FileAudio;
+    case 'none': return /^(application\/(msword|vnd\.|rtf)|text\/)/.test(type) ? FileText : FileIcon;
+    default: return FileText;
+  }
+}
+
+interface Props {
+  parts: PreviewPart[];
+  /** Opens a part; the row shows a spinner until the promise settles. */
+  onOpen: (part: PreviewPart) => Promise<void>;
+  /** Above the rows (an .eml's body, an archive's summary). */
+  header?: React.ReactElement;
+  /** Renders as a plain column inside a parent ScrollView instead of a list of its own. */
+  inline?: boolean;
+}
+
+/**
+ * The files inside an archive or an embedded message, each opening in the
+ * file preview like any attachment.
+ */
+export function PreviewPartList({ parts, onOpen, header, inline = false }: Props) {
+  const c = useColors();
+  const styles = React.useMemo(() => makeStyles(c), [c]);
+  const [busy, setBusy] = React.useState<string | null>(null);
+
+  const open = (part: PreviewPart) => {
+    if (busy) return;
+    setBusy(part.key);
+    onOpen(part).finally(() => setBusy(null));
+  };
+
+  const renderRow = (part: PreviewPart) => {
+    const Icon = iconFor(part);
+    return (
+      <Pressable
+        key={part.key}
+        style={({ pressed }) => [styles.row, pressed && styles.rowPressed]}
+        onPress={() => open(part)}
+        disabled={!!busy}
+        accessibilityRole="button"
+        accessibilityLabel={part.name}
+      >
+        <View style={styles.icon}>
+          {busy === part.key ? <ActivityIndicator size="small" color={c.textMuted} /> : <Icon size={20} color={c.textMuted} />}
+        </View>
+        <View style={styles.text}>
+          <Text style={styles.name} numberOfLines={1}>{part.name}</Text>
+          {part.folder ? <Text style={styles.folder} numberOfLines={1}>{part.folder}</Text> : null}
+        </View>
+        {part.size != null ? <Text style={styles.size}>{formatSize(part.size) || '0 B'}</Text> : null}
+      </Pressable>
+    );
+  };
+
+  if (inline) {
+    return (
+      <View style={styles.inline}>
+        {header}
+        {parts.map(renderRow)}
+      </View>
+    );
+  }
+  return (
+    <FlatList
+      style={styles.list}
+      data={parts}
+      keyExtractor={(p) => p.key}
+      renderItem={({ item }) => renderRow(item)}
+      ListHeaderComponent={header}
+      initialNumToRender={30}
+    />
+  );
+}
+
+/** The summary line above an archive's entries. */
+export function ArchiveSummary({ count, truncated }: { count: number; truncated: boolean }) {
+  const c = useColors();
+  const styles = React.useMemo(() => makeStyles(c), [c]);
+  const t = useLocaleStore((s) => s.t);
+  return (
+    <Text style={styles.summary}>
+      {truncated
+        ? t('email_viewer.preview.archive_first_files', 'The first {count} files', { count })
+        : t('email_viewer.preview.archive_files', '{count, plural, one {# file} other {# files}}', { count })}
+    </Text>
+  );
+}
+
+function makeStyles(c: ThemePalette) {
+  return StyleSheet.create({
+    list: { flex: 1 },
+    inline: { paddingBottom: spacing.lg },
+    row: {
+      flexDirection: 'row',
+      alignItems: 'center',
+      gap: spacing.md,
+      paddingHorizontal: spacing.lg,
+      paddingVertical: spacing.sm,
+      minHeight: 52,
+    },
+    rowPressed: { backgroundColor: c.surfaceHover },
+    icon: {
+      width: 36,
+      height: 36,
+      borderRadius: radius.md,
+      backgroundColor: c.surface,
+      alignItems: 'center',
+      justifyContent: 'center',
+    },
+    text: { flex: 1, minWidth: 0 },
+    name: { ...typography.body, color: c.text },
+    folder: { ...typography.caption, color: c.textMuted },
+    size: { ...typography.caption, color: c.textMuted },
+    summary: {
+      ...typography.caption,
+      color: c.textMuted,
+      paddingHorizontal: spacing.lg,
+      paddingTop: spacing.md,
+      paddingBottom: spacing.xs,
+    },
+  });
+}

src/components/email/use-body-override.ts

@@ -60,16 +60,18 @@ export interface EmlPreview {
   date?: string;
   html: string | null;
   text: string | null;
+  /** The message's own attachments (not the images its body embeds). */
+  attachments: ExtractedAttachment[];
 }
 
 /** Parse a message once for the preview: its unwrapped body plus the header lines shown above it. */
 export async function emlPreviewFromBytes(bytes: Uint8Array): Promise<EmlPreview> {
   const parsed = await parseMessage(bytes);
-  const { html, text } = unwrapParsed(parsed);
+  const { html, text, attachments } = unwrapParsed(parsed);
   const from = parsed.from && 'address' in parsed.from
     ? `${parsed.from.name ? `${parsed.from.name} ` : ''}<${parsed.from.address}>`
     : parsed.from?.name;
-  return { subject: parsed.subject, from, date: parsed.date, html, text };
+  return { subject: parsed.subject, from, date: parsed.date, html, text, attachments };
 }
 
 function unwrapParsed(parsed: ParsedEmail): UnwrappedMessage {

src/components/email/use-file-preview.ts

@@ -1,6 +1,6 @@
 import React from 'react';
 import { Alert, Platform } from 'react-native';
-import type { File } from 'expo-file-system';
+import { File } from 'expo-file-system';
 import type { Email } from '../../api/types';
 import {
   cachePreviewFile, copyPreviewFile, discardPreviewFile, saveLocalFileCopy, shareAttachment,
@@ -9,12 +9,17 @@ import {
 import {
   exceedsPreviewLimit, inAppPreviewKind, type FilePreviewOptions,
 } from '../../lib/file-preview';
-import type { PreviewKind } from '../../lib/attachment-display';
+import type { PreviewKind } from '../../lib/file-preview';
+import { markdownToHtml } from '../../lib/markdown-html';
+import { imageViewerHtml, mediaViewerHtml, pdfViewerHtml, type ViewerColors } from '../../lib/preview-viewer-html';
+import { closePdfPages, openPdfPages, PdfOpenError } from '../../lib/pdf-pages';
+import { openZip, ZipEncryptedError } from '../../lib/zip-preview';
 import { useLocaleStore } from '../../stores/locale-store';
+import { useColors, useResolvedTheme } from '../../theme/colors';
 import type { PreviewItem } from './AttachmentPreviewModal';
 import { emlPreviewFromBytes } from './use-body-override';
 
-export const PREVIEW_OPTIONS: FilePreviewOptions = { inlinePdf: Platform.OS === 'ios' };
+export const PREVIEW_OPTIONS: FilePreviewOptions = { platform: Platform.OS === 'ios' ? 'ios' : 'android' };
 
 interface PreviewSourceBase {
   /** Display name, shown in the header and given to the cached copy. */
@@ -62,20 +67,64 @@ function handOff(source: PreviewSource): Promise<void> {
   }
 }
 
+// The viewer page sits next to the file it shows (see preview-viewer-html).
+function writeViewer(local: File, html: string): string {
+  const page = new File(local.parentDirectory, '__preview.html');
+  if (page.exists) page.delete();
+  page.create();
+  page.write(html);
+  return page.uri;
+}
+
+interface Notices {
+  tooLarge: string;
+  pdfProtected: string;
+  pdfUnreadable: string;
+  zipProtected: string;
+  zipUnreadable: string;
+}
+
 async function buildItem(
   kind: Exclude<PreviewKind, 'none'>,
   source: PreviewSource,
   local: File,
-  tooLarge: string,
+  notices: Notices,
+  colors: ViewerColors,
 ): Promise<PreviewItem> {
   const base = { name: source.name, mimeType: source.type };
   // The source may not know its size; the copy does.
-  if (exceedsPreviewLimit(kind, local.size)) return { ...base, kind: 'none', notice: tooLarge };
+  if (exceedsPreviewLimit(kind, local.size)) return { ...base, kind: 'none', notice: notices.tooLarge };
   switch (kind) {
     case 'text':
       return { ...base, kind, text: await local.text() };
+    case 'markdown':
+      return { ...base, kind, html: markdownToHtml(await local.text()) };
+    case 'html':
+      return { ...base, kind, html: await local.text() };
     case 'eml':
       return { ...base, kind, eml: await emlPreviewFromBytes(await local.bytes()) };
+    case 'archive':
+      try {
+        return { ...base, kind, archive: await openZip(await local.bytes()) };
+      } catch (e) {
+        return { ...base, kind: 'none', notice: e instanceof ZipEncryptedError ? notices.zipProtected : notices.zipUnreadable };
+      }
+    case 'image':
+      return { ...base, kind, fileUri: local.uri, viewerUri: writeViewer(local, imageViewerHtml(local.name, colors)) };
+    case 'video':
+    case 'audio':
+      return { ...base, kind, fileUri: local.uri, viewerUri: writeViewer(local, mediaViewerHtml(kind, local.name, colors)) };
+    case 'pdf': {
+      // iOS's WebView shows the PDF itself; Android renders its pages.
+      if (Platform.OS !== 'android') return { ...base, kind, fileUri: local.uri };
+      try {
+        const pages = await openPdfPages(local.uri);
+        return { ...base, kind, fileUri: local.uri, viewerUri: writeViewer(local, pdfViewerHtml(local.name, pages, colors)) };
+      } catch (e) {
+        const protectedPdf = e instanceof PdfOpenError && e.reason === 'protected';
+        return { ...base, kind: 'none', notice: protectedPdf ? notices.pdfProtected : notices.pdfUnreadable };
+      }
+    }
     default:
       return { ...base, kind, fileUri: local.uri };
   }
@@ -97,6 +146,12 @@ export function useFilePreview(opts: {
   onClose?: () => void;
 } = {}) {
   const t = useLocaleStore((s) => s.t);
+  const c = useColors();
+  const scheme = useResolvedTheme();
+  // Read when a preview is built; the viewer page keeps the theme it opened with.
+  const viewerColors: ViewerColors = { scheme, background: c.background, text: c.text, textMuted: c.textMuted, surface: c.surface };
+  const colors = React.useRef(viewerColors);
+  colors.current = viewerColors;
   const onCloseRef = React.useRef(opts.onClose);
   onCloseRef.current = opts.onClose;
   const [item, setItem] = React.useState<PreviewItem | null>(null);
@@ -113,7 +168,9 @@ export function useFilePreview(opts: {
     seq.current += 1;
     const open = session.current;
     session.current = null;
-    if (open && !open.handedOff) discardPreviewFile(open.file);
+    if (!open) return;
+    closePdfPages(open.file.uri);
+    if (!open.handedOff) discardPreviewFile(open.file);
   }, []);
   React.useEffect(() => end, [end]);
 
@@ -153,8 +210,22 @@ export function useFilePreview(opts: {
           return;
         }
         session.current = { file: local, handedOff: false };
-        const next = await buildItem(kind, src, local, t('files.preview_too_large', 'This file is too large to preview.'));
+        const next = await buildItem(kind, src, local, {
+          tooLarge: t('files.preview_too_large', 'This file is too large to preview.'),
+          pdfProtected: t(
+            'email_viewer.preview.pdf_protected',
+            'This PDF is password-protected. Open it in another app to enter the password.',
+          ),
+          pdfUnreadable: t('email_viewer.preview.pdf_unreadable', "This PDF can't be shown here."),
+          zipProtected: t(
+            'email_viewer.preview.archive_protected',
+            'This archive is password-protected. Open it in another app to enter the password.',
+          ),
+          zipUnreadable: t('email_viewer.preview.archive_unreadable', "This archive can't be opened here."),
+        }, colors.current);
         if (current()) setItem(next);
+        // Closed while the PDF was opening: end() ran before the document was.
+        else closePdfPages(local.uri);
       } catch (e) {
         if (!current()) return;
         close();

src/lib/__tests__/attachment-display.test.ts

@@ -1,6 +1,6 @@
 import { describe, it, expect } from 'vitest';
 import {
-  getAttachmentDisplayName, visibleAttachments, previewKindFor, isReportPart, isRfc822Attachment,
+  getAttachmentDisplayName, visibleAttachments, isReportPart, isRfc822Attachment,
   isEmbeddedInBody,
 } from '../attachment-display';
 import { buildForwardAsAttachmentPayload } from '../forward-as-attachment';
@@ -93,16 +93,8 @@ describe('isEmbeddedInBody', () => {
   });
 });
 
-describe('previewKindFor / classification', () => {
-  it('classifies previewable types and refuses script-bearing ones', () => {
-    expect(previewKindFor({ type: 'image/jpeg', name: 'a.jpg' })).toBe('image');
-    expect(previewKindFor({ type: 'application/pdf', name: 'a.pdf' })).toBe('pdf');
-    expect(previewKindFor({ type: 'text/plain', name: 'a.txt' })).toBe('text');
-    expect(previewKindFor({ type: 'application/octet-stream', name: 'notes.md' })).toBe('text');
-    expect(previewKindFor({ type: 'message/rfc822', name: 'fwd.eml' })).toBe('eml');
-    expect(previewKindFor({ type: 'text/html', name: 'a.html' })).toBe('none');
-    expect(previewKindFor({ type: 'image/svg+xml', name: 'a.svg' })).toBe('none');
-    expect(previewKindFor({ type: 'application/zip', name: 'a.zip' })).toBe('none');
+describe('report and embedded-message parts', () => {
+  it('recognises DSN reports and .eml parts', () => {
     expect(isReportPart('message/delivery-status')).toBe(true);
     expect(isRfc822Attachment({ type: 'application/octet-stream', name: 'x.eml' })).toBe(true);
   });

src/lib/__tests__/file-preview.test.ts

@@ -1,52 +1,80 @@
 import { describe, it, expect } from 'vitest';
 import {
   filePreviewKind, inAppPreviewKind, exceedsPreviewLimit, FILE_PREVIEW_MAX_BYTES,
+  needsNativeImageDecoder, needsWebImageViewer, handoffMimeType,
 } from '../file-preview';
 
-const IOS = { inlinePdf: true };
-const ANDROID = { inlinePdf: false };
+const IOS = { platform: 'ios' } as const;
+const ANDROID = { platform: 'android' } as const;
 
 describe('filePreviewKind', () => {
-  it('previews the images React Native decodes, by type or by extension', () => {
+  it('previews common images by type or by extension', () => {
     expect(filePreviewKind({ name: 'photo.jpg', type: 'image/jpeg' }, ANDROID)).toBe('image');
     expect(filePreviewKind({ name: 'scan.PNG', type: 'application/octet-stream' }, ANDROID)).toBe('image');
     expect(filePreviewKind({ name: 'IMG_0001', type: 'image/heic' }, ANDROID)).toBe('image');
     expect(filePreviewKind({ name: 'anim.webp', type: '' }, ANDROID)).toBe('image');
   });
 
-  it('hands images it cannot decode to another app', () => {
+  it('draws SVG and ICO images instead of handing them off', () => {
+    expect(filePreviewKind({ name: 'logo.svg', type: 'image/svg+xml' }, IOS)).toBe('image');
+    expect(filePreviewKind({ name: 'logo.svg', type: 'application/octet-stream' }, ANDROID)).toBe('image');
+    expect(filePreviewKind({ name: 'favicon.ico', type: 'image/x-icon' }, ANDROID)).toBe('image');
+    expect(filePreviewKind({ name: 'logo.svgz', type: 'image/svg+xml' }, IOS)).toBe('none');
+  });
+
+  it('shows TIFF only where the platform decodes it', () => {
+    expect(filePreviewKind({ name: 'fax.tiff', type: 'image/tiff' }, IOS)).toBe('image');
+    expect(filePreviewKind({ name: 'fax.tif', type: '' }, IOS)).toBe('image');
     expect(filePreviewKind({ name: 'fax.tiff', type: 'image/tiff' }, ANDROID)).toBe('none');
     expect(filePreviewKind({ name: 'raw.cr2', type: 'image/x-canon-cr2' }, ANDROID)).toBe('none');
   });
 
-  it('keeps script-bearing documents out of the preview', () => {
-    expect(filePreviewKind({ name: 'logo.svg', type: 'image/svg+xml' }, IOS)).toBe('none');
-    expect(filePreviewKind({ name: 'page.html', type: 'text/html' }, IOS)).toBe('none');
-    expect(filePreviewKind({ name: 'page.htm', type: 'application/octet-stream' }, IOS)).toBe('none');
-    expect(filePreviewKind({ name: 'doc', type: 'application/xhtml+xml' }, IOS)).toBe('none');
+  it('renders HTML and Markdown documents', () => {
+    expect(filePreviewKind({ name: 'page.html', type: 'text/html' }, IOS)).toBe('html');
+    expect(filePreviewKind({ name: 'page.htm', type: 'application/octet-stream' }, ANDROID)).toBe('html');
+    expect(filePreviewKind({ name: 'doc', type: 'application/xhtml+xml' }, IOS)).toBe('html');
+    expect(filePreviewKind({ name: 'README.md', type: 'application/octet-stream' }, ANDROID)).toBe('markdown');
+    expect(filePreviewKind({ name: 'notes', type: 'text/markdown' }, ANDROID)).toBe('markdown');
   });
 
-  it('shows PDFs in-app only where the platform renders them', () => {
+  it('shows PDFs in-app on both platforms', () => {
     expect(filePreviewKind({ name: 'report.pdf', type: 'application/pdf' }, IOS)).toBe('pdf');
     expect(filePreviewKind({ name: 'report.pdf', type: 'application/octet-stream' }, IOS)).toBe('pdf');
-    expect(filePreviewKind({ name: 'report.pdf', type: 'application/pdf' }, ANDROID)).toBe('none');
+    expect(filePreviewKind({ name: 'report.pdf', type: 'application/pdf' }, ANDROID)).toBe('pdf');
+    expect(filePreviewKind({ name: 'REPORT.PDF', type: '' }, ANDROID)).toBe('pdf');
   });
 
-  it('shows plain text, markdown and data files as text', () => {
+  it('plays the video formats each platform plays', () => {
+    expect(filePreviewKind({ name: 'clip.mp4', type: 'video/mp4' }, IOS)).toBe('video');
+    expect(filePreviewKind({ name: 'clip.mov', type: 'video/quicktime' }, IOS)).toBe('video');
+    expect(filePreviewKind({ name: 'clip.mp4', type: 'video/mp4' }, ANDROID)).toBe('video');
+    expect(filePreviewKind({ name: 'clip.webm', type: 'video/webm' }, ANDROID)).toBe('video');
+    expect(filePreviewKind({ name: 'clip.mkv', type: 'application/octet-stream' }, ANDROID)).toBe('video');
+    expect(filePreviewKind({ name: 'clip.webm', type: 'video/webm' }, IOS)).toBe('none');
+    expect(filePreviewKind({ name: 'old.avi', type: 'video/x-msvideo' }, ANDROID)).toBe('none');
+    expect(filePreviewKind({ name: 'old.wmv', type: 'video/x-ms-wmv' }, IOS)).toBe('none');
+  });
+
+  it('plays the audio formats each platform plays', () => {
+    expect(filePreviewKind({ name: 'song.mp3', type: 'audio/mpeg' }, IOS)).toBe('audio');
+    expect(filePreviewKind({ name: 'voice.m4a', type: '' }, IOS)).toBe('audio');
+    expect(filePreviewKind({ name: 'memo.ogg', type: 'audio/ogg' }, ANDROID)).toBe('audio');
+    expect(filePreviewKind({ name: 'memo.ogg', type: 'application/octet-stream' }, ANDROID)).toBe('audio');
+    expect(filePreviewKind({ name: 'memo.opus', type: 'audio/ogg' }, IOS)).toBe('none');
+    expect(filePreviewKind({ name: 'call.amr', type: 'audio/amr' }, ANDROID)).toBe('none');
+  });
+
+  it('shows plain text, data and source files as text', () => {
     expect(filePreviewKind({ name: 'notes.txt', type: 'text/plain' }, ANDROID)).toBe('text');
-    expect(filePreviewKind({ name: 'README.md', type: 'application/octet-stream' }, ANDROID)).toBe('text');
     expect(filePreviewKind({ name: 'data.csv', type: 'text/csv' }, ANDROID)).toBe('text');
     expect(filePreviewKind({ name: 'config', type: 'application/json' }, ANDROID)).toBe('text');
     expect(filePreviewKind({ name: 'feed', type: 'application/atom+xml' }, ANDROID)).toBe('text');
-  });
-
-  it('shows source code as text, including the script types the reader leaves out', () => {
     expect(filePreviewKind({ name: 'app.ts', type: 'application/octet-stream' }, ANDROID)).toBe('text');
     expect(filePreviewKind({ name: 'main.py', type: '' }, ANDROID)).toBe('text');
     expect(filePreviewKind({ name: 'build.sh', type: 'application/x-sh' }, ANDROID)).toBe('text');
     expect(filePreviewKind({ name: 'index.js', type: 'text/javascript' }, ANDROID)).toBe('text');
-    expect(filePreviewKind({ name: 'bundle', type: 'application/javascript' }, ANDROID)).toBe('text');
     expect(filePreviewKind({ name: 'Dockerfile', type: '' }, ANDROID)).toBe('text');
+    expect(filePreviewKind({ name: 'invite.ics', type: 'text/calendar' }, IOS)).toBe('text');
   });
 
   it('shows saved messages like the reader does', () => {
@@ -54,10 +82,29 @@ describe('filePreviewKind', () => {
     expect(filePreviewKind({ name: 'fwd', type: 'message/rfc822' }, ANDROID)).toBe('eml');
   });
 
-  it('leaves binaries and office documents to other apps', () => {
-    expect(filePreviewKind({ name: 'archive.zip', type: 'application/zip' }, IOS)).toBe('none');
+  it('goes by the name when the declared type is a catch-all', () => {
+    expect(filePreviewKind({ name: 'invoice.pdf', type: 'application/x-as400attachment' }, IOS)).toBe('pdf');
+    expect(filePreviewKind({ name: 'photo.jpg', type: 'application/x-as400attachment' }, ANDROID)).toBe('image');
+    expect(filePreviewKind({ name: 'download', type: 'image/png' }, ANDROID)).toBe('image');
+  });
+
+  it('lets a media type decide over the name', () => {
+    expect(filePreviewKind({ name: 'clip.avi', type: 'video/mp4' }, ANDROID)).toBe('video');
+    expect(filePreviewKind({ name: 'cover.mp3', type: 'image/jpeg' }, ANDROID)).toBe('image');
+  });
+
+  it('lists the files in a ZIP, but not in the formats built on ZIP', () => {
+    expect(filePreviewKind({ name: 'archive.zip', type: 'application/zip' }, IOS)).toBe('archive');
+    expect(filePreviewKind({ name: 'photos', type: 'application/x-zip-compressed' }, ANDROID)).toBe('archive');
+    expect(filePreviewKind({ name: 'Archive.ZIP', type: 'application/octet-stream' }, ANDROID)).toBe('archive');
+    expect(filePreviewKind({ name: 'app.apk', type: 'application/vnd.android.package-archive' }, ANDROID)).toBe('none');
+  });
+
+  it('leaves other archives, office documents and binaries to other apps', () => {
+    expect(filePreviewKind({ name: 'backup.7z', type: 'application/x-7z-compressed' }, IOS)).toBe('none');
+    expect(filePreviewKind({ name: 'logs.tar.gz', type: 'application/gzip' }, ANDROID)).toBe('none');
     expect(filePreviewKind({ name: 'sheet.xlsx', type: 'application/octet-stream' }, IOS)).toBe('none');
-    expect(filePreviewKind({ name: 'movie.mp4', type: 'video/mp4' }, IOS)).toBe('none');
+    expect(filePreviewKind({ name: 'contract.docx', type: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document' }, ANDROID)).toBe('none');
     expect(filePreviewKind({ name: 'data.bin', type: undefined }, IOS)).toBe('none');
   });
 
@@ -67,11 +114,26 @@ describe('filePreviewKind', () => {
   });
 });
 
+describe('image viewer choice', () => {
+  it('sends formats Chromium cannot decode to the native decoder', () => {
+    expect(needsNativeImageDecoder({ name: 'IMG.HEIC', type: '' })).toBe(true);
+    expect(needsNativeImageDecoder({ name: 'x', type: 'image/heif' })).toBe(true);
+    expect(needsNativeImageDecoder({ name: 'photo.jpg', type: 'image/jpeg' })).toBe(false);
+  });
+
+  it('sends formats React Native cannot draw to the WebView', () => {
+    expect(needsWebImageViewer({ name: 'logo.svg', type: '' })).toBe(true);
+    expect(needsWebImageViewer({ name: 'x', type: 'image/x-icon' })).toBe(true);
+    expect(needsWebImageViewer({ name: 'photo.jpg', type: 'image/jpeg' })).toBe(false);
+  });
+});
+
 describe('preview size limits', () => {
-  it('caps text far below images and PDFs', () => {
+  it('caps text far below images, PDFs and media', () => {
     expect(FILE_PREVIEW_MAX_BYTES.text).toBe(512 * 1024);
     expect(FILE_PREVIEW_MAX_BYTES.text).toBeLessThan(FILE_PREVIEW_MAX_BYTES.image);
     expect(FILE_PREVIEW_MAX_BYTES.image).toBeLessThan(FILE_PREVIEW_MAX_BYTES.pdf);
+    expect(FILE_PREVIEW_MAX_BYTES.pdf).toBeLessThan(FILE_PREVIEW_MAX_BYTES.video);
   });
 
   it('flags only known sizes over the cap', () => {
@@ -89,5 +151,27 @@ describe('preview size limits', () => {
     expect(inAppPreviewKind({ ...big, size: undefined }, ANDROID)).toBe('text');
     expect(inAppPreviewKind({ name: 'pano.jpg', type: 'image/jpeg', size: 40 * 1024 * 1024 }, ANDROID)).toBe('none');
     expect(inAppPreviewKind({ name: 'pano.jpg', type: 'image/jpeg', size: 4 * 1024 * 1024 }, ANDROID)).toBe('image');
+    expect(inAppPreviewKind({ name: 'film.mp4', type: 'video/mp4', size: 300 * 1024 * 1024 }, ANDROID)).toBe('video');
+  });
+});
+
+describe('handoffMimeType', () => {
+  it('keeps a real declared type', () => {
+    expect(handoffMimeType('a.pdf', 'application/pdf')).toBe('application/pdf');
+    expect(handoffMimeType('scan', 'image/png')).toBe('image/png');
+    expect(handoffMimeType('a.zip', 'application/x-zip-compressed')).toBe('application/zip');
+  });
+
+  it('names the format when the declared type does not, so Android finds a viewer', () => {
+    expect(handoffMimeType('contract.docx', 'application/octet-stream'))
+      .toBe('application/vnd.openxmlformats-officedocument.wordprocessingml.document');
+    expect(handoffMimeType('invoice.PDF', '')).toBe('application/pdf');
+    expect(handoffMimeType('invoice.pdf', 'application/x-as400attachment')).toBe('application/pdf');
+    expect(handoffMimeType('photo.jpg', 'application/x-unknown')).toBe('image/jpeg');
+  });
+
+  it('falls back to the declared type or octet-stream for unknown names', () => {
+    expect(handoffMimeType('data.bin', '')).toBe('application/octet-stream');
+    expect(handoffMimeType('data.xyz', 'application/x-foo')).toBe('application/x-foo');
   });
 });

src/lib/__tests__/markdown-html.test.ts

@@ -0,0 +1,70 @@
+import { describe, it, expect } from 'vitest';
+import { markdownToHtml, renderInline } from '../markdown-html';
+
+const body = (md: string) => {
+  const html = markdownToHtml(md);
+  return html.slice(html.indexOf('<body>') + 6, html.indexOf('</body>'));
+};
+
+describe('markdownToHtml', () => {
+  it('renders headings, paragraphs and rules', () => {
+    expect(body('# Title\n\nSome text\nwrapped.\n\n---\n\n### Small ###'))
+      .toBe('<h1>Title</h1>\n<p>Some text\nwrapped.</p>\n<hr>\n<h3>Small</h3>');
+    expect(body('Big\n===\n\nSmaller\n---')).toBe('<h1>Big</h1>\n<h2>Smaller</h2>');
+  });
+
+  it('renders nested and ordered lists and task items', () => {
+    expect(body('- one\n- two\n  - nested\n- three')).toBe(
+      '<ul><li>one</li><li>two\n<ul><li>nested</li></ul></li><li>three</li></ul>',
+    );
+    expect(body('3. c\n4. d')).toBe('<ol start="3"><li>c</li><li>d</li></ol>');
+    expect(body('- [x] done\n- [ ] open')).toBe('<ul><li class="task">\u2611 done</li><li class="task">\u2610 open</li></ul>');
+  });
+
+  it('keeps fenced and indented code verbatim and escaped', () => {
+    expect(body('```js\nconst a = "<b>";\n**not bold**\n```')).toBe(
+      '<pre><code class="language-js">const a = &quot;&lt;b&gt;&quot;;\n**not bold**</code></pre>',
+    );
+    expect(body('    x < 1')).toBe('<pre><code>x &lt; 1</code></pre>');
+  });
+
+  it('renders quotes and GFM tables with alignment', () => {
+    expect(body('> quoted\n> **text**')).toBe('<blockquote><p>quoted\n<strong>text</strong></p></blockquote>');
+    expect(body('| a | b |\n|:--|--:|\n| 1 | 2 |')).toBe(
+      '<table><thead><tr><th style="text-align:left">a</th><th style="text-align:right">b</th></tr></thead>'
+      + '<tbody><tr><td style="text-align:left">1</td><td style="text-align:right">2</td></tr></tbody></table>',
+    );
+  });
+
+  it('escapes raw HTML instead of passing it through', () => {
+    expect(body('<script>alert(1)</script>')).toBe('<p>&lt;script&gt;alert(1)&lt;/script&gt;</p>');
+    expect(body('<img src=x onerror=alert(1)>')).not.toContain('<img');
+  });
+});
+
+describe('renderInline', () => {
+  it('renders emphasis, code and strikethrough', () => {
+    expect(renderInline('**b** *i* _j_ `c*d*` ~~s~~')).toBe(
+      '<strong>b</strong> <em>i</em> <em>j</em> <code>c*d*</code> <del>s</del>',
+    );
+    expect(renderInline('snake_case_name stays')).toBe('snake_case_name stays');
+    expect(renderInline('\\*literal\\*')).toBe('*literal*');
+  });
+
+  it('links only to web and mail URLs', () => {
+    expect(renderInline('[site](https://example.org "T")')).toBe('<a href="https://example.org" title="T">site</a>');
+    expect(renderInline('[x](javascript:alert(1))')).toBe('x)');
+    expect(renderInline('[doc](./docs/a.md)')).toBe('doc');
+    expect(renderInline('see https://example.org/a.')).toBe('see <a href="https://example.org/a">https://example.org/a</a>.');
+    expect(renderInline('<mailto:a@b.c>')).toBe('<a href="mailto:a@b.c">mailto:a@b.c</a>');
+  });
+
+  it('keeps image URLs for the sanitiser and drops unsafe ones', () => {
+    expect(renderInline('![logo](https://example.org/l.png)')).toBe('<img src="https://example.org/l.png" alt="logo">');
+    expect(renderInline('![x](data:image/png;base64,AAA)')).toBe('x');
+  });
+
+  it('escapes attribute breakouts in link text and titles', () => {
+    expect(renderInline('[a"b](https://e.org "x\\" onmouseover=\\"y")')).not.toMatch(/onmouseover="/);
+  });
+});

src/lib/__tests__/pdf-pages.test.ts

@@ -0,0 +1,42 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { NativeModules } from 'react-native';
+import { openPdfPages, PdfOpenError, renderPdfPage, canRenderPdfPages } from '../pdf-pages';
+
+const modules = NativeModules as Record<string, unknown>;
+
+function nativeError(code: string, message: string): Error {
+  return Object.assign(new Error(message), { code });
+}
+
+describe('pdf-pages', () => {
+  afterEach(() => { delete modules.BulwarkPdf; });
+
+  it('reports the page sizes the renderer returns', async () => {
+    modules.BulwarkPdf = { open: vi.fn(async () => ({ pages: [{ width: 595, height: 842 }] })) };
+    await expect(openPdfPages('file:///x.pdf')).resolves.toEqual([{ width: 595, height: 842 }]);
+  });
+
+  it('tells a password-protected PDF from an unreadable one', async () => {
+    modules.BulwarkPdf = { open: vi.fn(async () => { throw nativeError('E_PDF_PROTECTED', 'password'); }) };
+    await expect(openPdfPages('file:///x.pdf')).rejects.toMatchObject({ reason: 'protected' });
+
+    modules.BulwarkPdf = { open: vi.fn(async () => { throw nativeError('E_PDF_OPEN', 'not a PDF'); }) };
+    await expect(openPdfPages('file:///x.pdf')).rejects.toMatchObject({ reason: 'unreadable' });
+
+    modules.BulwarkPdf = { open: vi.fn(async () => ({ pages: [] })) };
+    await expect(openPdfPages('file:///x.pdf')).rejects.toBeInstanceOf(PdfOpenError);
+  });
+
+  it('fails cleanly in a build without the renderer', async () => {
+    expect(canRenderPdfPages()).toBe(false);
+    await expect(openPdfPages('file:///x.pdf')).rejects.toMatchObject({ reason: 'unreadable' });
+    await expect(renderPdfPage('file:///x.pdf', 0, 100, 'file:///p.png')).rejects.toThrow();
+  });
+
+  it('renders at a whole pixel width', async () => {
+    const renderPage = vi.fn(async () => 'file:///p.png');
+    modules.BulwarkPdf = { renderPage };
+    await renderPdfPage('file:///x.pdf', 2, 1620.6, 'file:///p.png');
+    expect(renderPage).toHaveBeenCalledWith('file:///x.pdf', 2, 1621, 'file:///p.png');
+  });
+});

src/lib/__tests__/preview-viewer-html.test.ts

@@ -0,0 +1,43 @@
+import { describe, it, expect } from 'vitest';
+import { imageViewerHtml, mediaViewerHtml, relativeFileUrl, type ViewerColors } from '../preview-viewer-html';
+
+const COLORS: ViewerColors = { scheme: 'dark', background: '#111', text: '#eee', textMuted: '#999', surface: '#222' };
+const HOSTILE = `x"><script>alert(1)</script>'.png`;
+
+describe('relativeFileUrl', () => {
+  it('encodes everything a URL or an attribute could read as syntax', () => {
+    expect(relativeFileUrl('Scan 1 (final).PNG')).toBe('Scan%201%20%28final%29.PNG');
+    expect(relativeFileUrl('a#b?c%d.jpg')).toBe('a%23b%3Fc%25d.jpg');
+    expect(relativeFileUrl(HOSTILE)).not.toMatch(/["'<>]/);
+  });
+});
+
+describe('viewer pages', () => {
+  it('load the file by a relative URL next to the page', () => {
+    expect(imageViewerHtml('photo 1.jpg', COLORS)).toContain('src="photo%201.jpg"');
+    expect(mediaViewerHtml('video', 'clip.mp4', COLORS)).toContain('<video id="m" src="clip.mp4"');
+    expect(mediaViewerHtml('audio', 'song.mp3', COLORS)).toContain('<audio id="m" src="song.mp3"');
+  });
+
+  it('never put a file name into markup unescaped', () => {
+    for (const html of [
+      imageViewerHtml(HOSTILE, COLORS),
+      mediaViewerHtml('video', HOSTILE, COLORS),
+      mediaViewerHtml('audio', HOSTILE, COLORS),
+    ]) {
+      expect(html).not.toContain('<script>alert(1)');
+      expect(html.match(/<script>/g)).toHaveLength(1);
+    }
+  });
+
+  it('report a file that does not decode', () => {
+    expect(imageViewerHtml('a.svg', COLORS)).toContain("addEventListener('error'");
+    expect(mediaViewerHtml('audio', 'a.ogg', COLORS)).toContain("report('error')");
+  });
+
+  it('draw the WebView controls in the app theme, and video on black', () => {
+    expect(mediaViewerHtml('audio', 'a.mp3', COLORS)).toContain('color-scheme:dark');
+    expect(mediaViewerHtml('audio', 'a.mp3', { ...COLORS, scheme: 'light' })).toContain('color-scheme:light');
+    expect(mediaViewerHtml('video', 'a.mp4', { ...COLORS, scheme: 'light' })).toContain('color-scheme:dark');
+  });
+});

src/lib/__tests__/zip-preview.test.ts

@@ -0,0 +1,72 @@
+import { describe, it, expect } from 'vitest';
+import JSZip from 'jszip';
+import { openZip, isZipArchive, ZipEncryptedError, MAX_ZIP_ENTRIES } from '../zip-preview';
+
+async function makeZip(files: Record<string, string>): Promise<Uint8Array> {
+  const zip = new JSZip();
+  for (const [path, text] of Object.entries(files)) zip.file(path, text);
+  return zip.generateAsync({ type: 'uint8array', compression: 'DEFLATE' });
+}
+
+// Set the "encrypted" bit in every local and central header, as a
+// password-protected archive has it.
+function markEncrypted(bytes: Uint8Array): Uint8Array {
+  const out = bytes.slice();
+  const view = new DataView(out.buffer);
+  for (let i = 0; i + 4 <= out.length; i++) {
+    const sig = view.getUint32(i, true);
+    if (sig === 0x04034b50) view.setUint16(i + 6, view.getUint16(i + 6, true) | 1, true);
+    if (sig === 0x02014b50) view.setUint16(i + 8, view.getUint16(i + 8, true) | 1, true);
+  }
+  return out;
+}
+
+describe('openZip', () => {
+  it('lists the files by folder and name, without folders or OS metadata', async () => {
+    const archive = await openZip(await makeZip({
+      'b.txt': 'b',
+      'docs/z.md': '# z',
+      'a.txt': 'a',
+      'docs/inner/c.csv': '1,2',
+      '__MACOSX/docs/._z.md': 'junk',
+      '.DS_Store': 'junk',
+      'docs/Thumbs.db': 'junk',
+    }));
+    expect(archive.entries.map((e) => e.path)).toEqual(['a.txt', 'b.txt', 'docs/z.md', 'docs/inner/c.csv']);
+    expect(archive.entries[2]).toMatchObject({ name: 'z.md', folder: 'docs', size: 3 });
+    expect(archive.truncated).toBe(false);
+  });
+
+  it('reads an entry from the loaded archive', async () => {
+    const archive = await openZip(await makeZip({ 'docs/notes.txt': 'Grüße' }));
+    expect(new TextDecoder().decode(await archive.read('docs/notes.txt'))).toBe('Grüße');
+    await expect(archive.read('missing.txt')).rejects.toThrow(/not in the archive/);
+  });
+
+  it('stops listing at the cap', async () => {
+    const files: Record<string, string> = {};
+    for (let i = 0; i < MAX_ZIP_ENTRIES + 5; i++) files[`f${i}.txt`] = '';
+    const archive = await openZip(await makeZip(files));
+    expect(archive.entries).toHaveLength(MAX_ZIP_ENTRIES);
+    expect(archive.truncated).toBe(true);
+  });
+
+  it('says when an archive is password-protected', async () => {
+    const locked = markEncrypted(await makeZip({ 'secret.txt': 'x' }));
+    await expect(openZip(locked)).rejects.toBeInstanceOf(ZipEncryptedError);
+  });
+
+  it('rejects data that is not a ZIP', async () => {
+    await expect(openZip(new TextEncoder().encode('not a zip'))).rejects.not.toBeInstanceOf(ZipEncryptedError);
+  });
+});
+
+describe('isZipArchive', () => {
+  it('takes ZIPs by type or name, not the formats built on ZIP', () => {
+    expect(isZipArchive('a.zip', 'application/zip')).toBe(true);
+    expect(isZipArchive('bundle', 'application/x-zip-compressed')).toBe(true);
+    expect(isZipArchive('Archive.ZIP', 'application/octet-stream')).toBe(true);
+    expect(isZipArchive('contract.docx', 'application/vnd.openxmlformats-officedocument.wordprocessingml.document')).toBe(false);
+    expect(isZipArchive('app.apk', 'application/vnd.android.package-archive')).toBe(false);
+  });
+});

src/lib/attachment-display.ts

@@ -140,24 +140,6 @@ export function calendarBannerShownFor(email: Pick<Email, 'attachments'>, parsin
   return parsingEnabled && !!findCalendarAttachment(email);
 }
 
-export type PreviewKind = 'image' | 'pdf' | 'text' | 'eml' | 'none';
-
-const TEXT_EXT = /\.(txt|md|markdown|csv|log|json|xml|ics|vcf|yml|yaml|ini|conf|diff|patch)$/i;
-// Script-bearing types are never previewed inline (html/svg/js) - webmail lib/file-preview.ts.
-const SCRIPT_TYPES = /^(text\/html|image\/svg\+xml|application\/(x-)?javascript|text\/javascript|application\/xhtml\+xml)$/i;
-
-/** How the in-app preview should render a part, if at all. */
-export function previewKindFor(att: Pick<Attachment, 'name' | 'type'>): PreviewKind {
-  const base = (att.type || '').split(';')[0].trim().toLowerCase();
-  const name = att.name || '';
-  if (SCRIPT_TYPES.test(base) || /\.(html?|svg|js)$/i.test(name)) return 'none';
-  if (isRfc822Attachment(att)) return 'eml';
-  if (base.startsWith('image/') || /\.(png|jpe?g|gif|webp|bmp|heic|avif)$/i.test(name)) return 'image';
-  if (base === 'application/pdf' || /\.pdf$/i.test(name)) return 'pdf';
-  if (base.startsWith('text/') || base === 'application/json' || base === 'application/xml' || TEXT_EXT.test(name)) return 'text';
-  return 'none';
-}
-
 export function formatSize(bytes?: number): string {
   if (!bytes) return '';
   if (bytes < 1024) return `${bytes} B`;

src/lib/email-export.ts

@@ -14,6 +14,7 @@ import {
 } from './download-filename';
 import { getClientCertAlias, secureFetch } from './client-cert';
 import { sniffImageMime } from './email-html';
+import { handoffMimeType } from './file-preview';
 
 const RFC822 = 'message/rfc822';
 const FLAG_GRANT_READ_URI_PERMISSION = 0x00000001;
@@ -156,7 +157,7 @@ async function openWithViewer(file: File, mimeType: string): Promise<boolean> {
       // intent. Deliberately no FLAG_ACTIVITY_NEW_TASK: expo-intent-launcher
       // uses startActivityForResult, and a new task cancels that result.
       data: file.contentUri,
-      type: mimeType,
+      type: handoffMimeType(file.name, mimeType),
       flags: FLAG_GRANT_READ_URI_PERMISSION,
     });
     return true;
@@ -259,7 +260,7 @@ export async function shareAttachment(
   }
   try {
     await Sharing.shareAsync(downloaded.uri, {
-      mimeType,
+      mimeType: handoffMimeType(filename, mimeType),
       dialogTitle: filename,
     });
   } finally {
@@ -296,7 +297,7 @@ async function offerSavedFile(file: File, filename: string, mimeType: string): P
     throw new Error(t('files.share_unavailable', 'Sharing is not available on this device'));
   }
   await Sharing.shareAsync(file.uri, {
-    mimeType,
+    mimeType: handoffMimeType(filename, mimeType),
     dialogTitle: filename,
   });
 }
@@ -422,7 +423,7 @@ export async function shareLocalFile(
     throw new Error(t('files.share_unavailable', 'Sharing is not available on this device'));
   }
   try {
-    await Sharing.shareAsync(file.uri, { mimeType, dialogTitle: dialogTitle ?? file.name });
+    await Sharing.shareAsync(file.uri, { mimeType: handoffMimeType(file.name, mimeType), dialogTitle: dialogTitle ?? file.name });
   } finally {
     if (!opts.keep) scheduleTempCleanup(file);
   }

src/lib/file-preview.ts

@@ -1,19 +1,19 @@
-// Which Files-tab nodes open in the in-app preview, and how large they may be.
-// Builds on the reader's attachment classification (`previewKindFor`) so both
-// previews agree, and adds what a drive holds more often than mail: source
-// code and config files, shown as text. Port of the webmail's
-// `lib/file-preview.ts`, narrowed to what the native preview can render;
-// everything else keeps going to the OS "Open with" chooser.
+// Which files open in the in-app preview, how, and how large they may be.
+// One classification for every place that opens a file: the reader's and the
+// list's attachment chips, the Files tab and compose. Port of the webmail's
+// `lib/file-preview.ts`, narrowed to what each platform's viewers render;
+// everything else goes to the OS "Open with" chooser.
 
-import { previewKindFor, type PreviewKind } from './attachment-display';
+export type PreviewKind =
+  | 'image' | 'pdf' | 'text' | 'markdown' | 'html' | 'eml' | 'video' | 'audio' | 'archive' | 'none';
 
 export interface FilePreviewOptions {
   /**
-   * Whether this platform renders PDFs in-app. iOS does, in the WebView;
-   * Android has no built-in renderer, so a PDF there goes straight to the
-   * PDF viewer instead of a preview screen that can only offer that viewer.
+   * The platform's viewers decide what plays: video and audio play in the
+   * system WebView (Chromium on Android, WebKit on iOS), whose formats
+   * differ.
    */
-  inlinePdf: boolean;
+  platform: 'ios' | 'android';
 }
 
 interface PreviewableFile {
@@ -24,74 +24,137 @@ interface PreviewableFile {
 
 /**
  * Largest file each preview kind loads. Text is rendered in one selectable
- * `<Text>`, which gets slow to lay out past a few hundred KB; parsing an
- * .eml and decoding an image hold the whole file in memory; PDFs are paged by
- * the WebView. Larger files open in another app instead.
+ * `<Text>`, which gets slow to lay out past a few hundred KB; HTML and
+ * Markdown go through the mail sanitiser in JS; parsing an .eml and decoding
+ * an image hold the whole file in memory, and so does listing a ZIP. PDFs
+ * are paged by their viewer and media stream from the downloaded copy.
+ * Larger files open in another app.
  */
 export const FILE_PREVIEW_MAX_BYTES: Record<Exclude<PreviewKind, 'none'>, number> = {
   text: 512 * 1024,
+  markdown: 1024 * 1024,
+  html: 5 * 1024 * 1024,
   eml: 10 * 1024 * 1024,
+  archive: 50 * 1024 * 1024,
   image: 25 * 1024 * 1024,
-  pdf: 50 * 1024 * 1024,
+  pdf: 100 * 1024 * 1024,
+  audio: 500 * 1024 * 1024,
+  video: 1024 * 1024 * 1024,
 };
 
-// Script-bearing documents open in the browser, as in the reader. The webmail
-// renders HTML in a sandboxed iframe and SVG through <img>; neither has a safe
-// native equivalent here.
-const NEVER_INLINE_MIME = new Set(['text/html', 'application/xhtml+xml', 'image/svg+xml']);
-const NEVER_INLINE_EXT = /\.(html?|xht(ml)?|svgz?)$/i;
-
-// Formats React Native's Image decodes. Other image types (TIFF, RAW, PSD,
-// ICO) would render blank.
-const RENDERABLE_IMAGE_MIME = new Set([
-  'image/png', 'image/jpeg', 'image/jpg', 'image/pjpeg', 'image/gif', 'image/webp',
-  'image/bmp', 'image/x-ms-bmp', 'image/heic', 'image/heif', 'image/avif',
-]);
-const RENDERABLE_IMAGE_EXT = /\.(png|jpe?g|jfif|gif|webp|bmp|heic|heif|avif)$/i;
-
-// Source and config files the reader's list doesn't cover (it only sees mail
-// attachments). The webmail's TEXT_EXTENSIONS plus the languages the Files
-// tab already draws a code icon for.
-const CODE_EXT = new RegExp(
-  '\\.('
-  + 'text|tsv|toml|cfg|env|properties|sql|graphql|gql|css|scss|sass|less'
-  + '|js|mjs|cjs|jsx|ts|mts|cts|tsx|vue|svelte'
-  + '|py|rb|go|rs|java|kt|kts|swift|c|h|cc|cpp|hpp|cs|php|pl|lua|r|dart|scala|gradle'
-  + '|sh|bash|zsh|fish|ps1|bat|cmd'
-  + '|tex|rst|adoc|org|srt|vtt'
-  + ')$',
-  'i',
-);
-const CODE_FILE_NAMES = new Set(['dockerfile', 'makefile', 'readme', 'license', 'changelog', '.gitignore', '.editorconfig']);
-const TEXT_MIME = new Set([
-  'application/json', 'application/ld+json', 'application/xml', 'application/javascript',
-  'application/x-javascript', 'text/javascript', 'application/typescript', 'application/x-sh',
-  'application/x-yaml', 'application/yaml', 'application/toml', 'application/sql', 'application/graphql',
-]);
-
 function baseMime(type?: string | null): string {
   return (type || '').split(';')[0].trim().toLowerCase();
 }
 
+function extension(name: string): string {
+  const dot = name.lastIndexOf('.');
+  return dot > 0 ? name.slice(dot + 1).toLowerCase() : '';
+}
+
+// Generic types say nothing about the file; the name decides.
+const GENERIC_MIME = new Set(['', 'application/octet-stream', 'binary/octet-stream', 'application/unknown']);
+
+// Images React Native's Image decodes, plus SVG and ICO, which the preview
+// draws in a WebView. iOS decodes TIFF as well; Android's decoders don't.
+const IMAGE_EXT = new Set(['png', 'jpg', 'jpeg', 'jfif', 'pjpeg', 'gif', 'webp', 'bmp', 'heic', 'heif', 'avif', 'svg', 'ico']);
+const IMAGE_MIME = new Set([
+  'image/png', 'image/jpeg', 'image/jpg', 'image/pjpeg', 'image/gif', 'image/webp', 'image/bmp',
+  'image/x-ms-bmp', 'image/heic', 'image/heif', 'image/avif', 'image/svg+xml', 'image/x-icon',
+  'image/vnd.microsoft.icon', 'image/ico',
+]);
+const IOS_IMAGE_EXT = new Set(['tif', 'tiff']);
+const IOS_IMAGE_MIME = new Set(['image/tiff', 'image/tif']);
+
+// What the system WebView plays. Chromium handles the open formats and
+// Matroska; WebKit handles Apple's, and neither plays AVI, WMV or FLV.
+const MEDIA: Record<'video' | 'audio', Record<FilePreviewOptions['platform'], { ext: Set<string>; mime: Set<string> }>> = {
+  video: {
+    android: {
+      ext: new Set(['mp4', 'm4v', 'mov', 'webm', 'ogv', 'mkv', '3gp', '3g2']),
+      mime: new Set(['video/mp4', 'video/x-m4v', 'video/quicktime', 'video/webm', 'video/ogg', 'video/x-matroska', 'video/3gpp', 'video/3gpp2']),
+    },
+    ios: {
+      ext: new Set(['mp4', 'm4v', 'mov', '3gp', '3g2']),
+      mime: new Set(['video/mp4', 'video/x-m4v', 'video/quicktime', 'video/3gpp', 'video/3gpp2']),
+    },
+  },
+  audio: {
+    android: {
+      ext: new Set(['mp3', 'm4a', 'aac', 'wav', 'ogg', 'oga', 'opus', 'flac', 'weba']),
+      mime: new Set([
+        'audio/mpeg', 'audio/mp3', 'audio/mp4', 'audio/x-m4a', 'audio/aac', 'audio/wav', 'audio/x-wav', 'audio/wave',
+        'audio/ogg', 'audio/opus', 'audio/flac', 'audio/x-flac', 'audio/webm',
+      ]),
+    },
+    ios: {
+      ext: new Set(['mp3', 'm4a', 'aac', 'wav', 'flac', 'aif', 'aiff', 'caf']),
+      mime: new Set([
+        'audio/mpeg', 'audio/mp3', 'audio/mp4', 'audio/x-m4a', 'audio/aac', 'audio/wav', 'audio/x-wav', 'audio/wave',
+        'audio/flac', 'audio/x-flac', 'audio/aiff', 'audio/x-aiff', 'audio/x-caf',
+      ]),
+    },
+  },
+};
+
+const ZIP_MIME = new Set(['application/zip', 'application/x-zip-compressed', 'application/x-zip']);
+const HTML_MIME = new Set(['text/html', 'application/xhtml+xml']);
+const HTML_EXT = new Set(['html', 'htm', 'xhtml', 'xht']);
+const MARKDOWN_MIME = new Set(['text/markdown', 'text/x-markdown']);
+const MARKDOWN_EXT = new Set(['md', 'markdown', 'mdown', 'mkd', 'mkdn']);
+
+// Plain text and source files, shown as text. Script types are inert there.
+const TEXT_EXT = new Set([
+  'txt', 'text', 'log', 'csv', 'tsv', 'json', 'xml', 'ics', 'vcf', 'yml', 'yaml', 'ini', 'conf', 'cfg', 'env',
+  'properties', 'toml', 'diff', 'patch', 'sql', 'graphql', 'gql', 'css', 'scss', 'sass', 'less',
+  'js', 'mjs', 'cjs', 'jsx', 'ts', 'mts', 'cts', 'tsx', 'vue', 'svelte',
+  'py', 'rb', 'go', 'rs', 'java', 'kt', 'kts', 'swift', 'c', 'h', 'cc', 'cpp', 'hpp', 'cs', 'php', 'pl', 'lua', 'r',
+  'dart', 'scala', 'gradle', 'sh', 'bash', 'zsh', 'fish', 'ps1', 'bat', 'cmd',
+  'tex', 'rst', 'adoc', 'org', 'srt', 'vtt',
+]);
+const TEXT_FILE_NAMES = new Set(['dockerfile', 'makefile', 'readme', 'license', 'changelog', '.gitignore', '.editorconfig']);
+const TEXT_MIME = new Set([
+  'application/json', 'application/ld+json', 'application/xml', 'application/javascript',
+  'application/x-javascript', 'application/typescript', 'application/x-sh', 'application/x-yaml',
+  'application/yaml', 'application/toml', 'application/sql', 'application/graphql',
+  'application/ics', 'application/icalendar',
+]);
+
 /** How the in-app preview renders a file, or 'none' for the OS chooser. */
 export function filePreviewKind(file: Pick<PreviewableFile, 'name' | 'type'>, opts: FilePreviewOptions): PreviewKind {
-  const mime = baseMime(file.type);
+  const declared = baseMime(file.type);
+  const mime = GENERIC_MIME.has(declared) ? '' : declared;
   const name = file.name || '';
-  if (NEVER_INLINE_MIME.has(mime) || NEVER_INLINE_EXT.test(name)) return 'none';
-  const kind = previewKindFor({ name, type: mime });
-  switch (kind) {
-    case 'image':
-      return RENDERABLE_IMAGE_MIME.has(mime) || RENDERABLE_IMAGE_EXT.test(name) ? 'image' : 'none';
-    case 'pdf':
-      return opts.inlinePdf ? 'pdf' : 'none';
-    case 'none':
-      // The reader keeps .js and friends out; shown as source text they are inert.
-      if (CODE_EXT.test(name) || CODE_FILE_NAMES.has(name.toLowerCase())) return 'text';
-      if (TEXT_MIME.has(mime) || /\+(json|xml)$/.test(mime)) return 'text';
-      return 'none';
-    default:
-      return kind;
+  const ext = extension(name);
+  // An image, audio or video type decides the viewer. Any other type leaves
+  // it to the name: senders put catch-alls such as the
+  // application/x-as400attachment IBM i systems use on every part.
+  const media = /^(image|audio|video)\//.test(mime);
+
+  if (mime === 'message/rfc822' || ext === 'eml') return 'eml';
+  // ZIPs list their files; formats built on ZIP (docx, apk) are not ZIPs here.
+  if (ZIP_MIME.has(mime) || ((!mime || mime.startsWith('application/x-')) && ext === 'zip')) return 'archive';
+  if (HTML_MIME.has(mime) || HTML_EXT.has(ext)) return 'html';
+  if (MARKDOWN_MIME.has(mime) || MARKDOWN_EXT.has(ext)) return 'markdown';
+
+  if (mime.startsWith('image/') || (!media && (IMAGE_EXT.has(ext) || IOS_IMAGE_EXT.has(ext)))) {
+    // Compressed SVG needs a Content-Encoding a local file doesn't have.
+    if (ext === 'svgz') return 'none';
+    const ios = opts.platform === 'ios';
+    const shown = IMAGE_MIME.has(mime) || IMAGE_EXT.has(ext)
+      || (ios && (IOS_IMAGE_MIME.has(mime) || IOS_IMAGE_EXT.has(ext)));
+    return shown ? 'image' : 'none';
   }
+  // iOS's WebView shows PDFs; Android renders their pages (pdf-pages.ts).
+  if (mime === 'application/pdf' || (!media && ext === 'pdf')) return 'pdf';
+  for (const kind of ['video', 'audio'] as const) {
+    const formats = MEDIA[kind][opts.platform];
+    if (mime.startsWith(`${kind}/`)) return formats.mime.has(mime) || formats.ext.has(ext) ? kind : 'none';
+    if (!media && formats.ext.has(ext)) return kind;
+  }
+
+  if (mime.startsWith('text/') || TEXT_MIME.has(mime) || /\+(json|xml)$/.test(mime)) return 'text';
+  if (TEXT_EXT.has(ext) || TEXT_FILE_NAMES.has(name.toLowerCase())) return 'text';
+  return 'none';
 }
 
 /** True when a known size is over the preview cap for `kind`. Unknown sizes pass; the caller checks the download. */
@@ -102,9 +165,99 @@ export function exceedsPreviewLimit(kind: PreviewKind, size: number | null | und
 
 /**
  * The preview a tap on this file opens: its kind when the app can show it and
- * the file is within the cap, else 'none' (hand it to another app, as before).
+ * the file is within the cap, else 'none' (hand it to another app).
  */
 export function inAppPreviewKind(file: PreviewableFile, opts: FilePreviewOptions): PreviewKind {
   const kind = filePreviewKind(file, opts);
   return exceedsPreviewLimit(kind, file.size) ? 'none' : kind;
 }
+
+/** Images Android's WebView can't decode, which the preview draws with React Native's Image instead. */
+export function needsNativeImageDecoder(file: Pick<PreviewableFile, 'name' | 'type'>): boolean {
+  const mime = baseMime(file.type);
+  return /^image\/(heic|heif|tiff?)$/.test(mime) || /\.(heic|heif|tiff?)$/i.test(file.name);
+}
+
+/** Images React Native's Image can't draw, which go to the WebView viewer on iOS too. */
+export function needsWebImageViewer(file: Pick<PreviewableFile, 'name' | 'type'>): boolean {
+  const mime = baseMime(file.type);
+  return /^image\/(svg\+xml|x-icon|vnd\.microsoft\.icon|ico)$/.test(mime) || /\.(svg|ico)$/i.test(file.name);
+}
+
+// Types for handing a file to another app when the sender declared none, or
+// a catch-all: Android picks the apps for "Open with" by type, and finds
+// none for application/octet-stream.
+const EXT_TO_MIME: Record<string, string> = {
+  pdf: 'application/pdf',
+  doc: 'application/msword',
+  docx: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
+  xls: 'application/vnd.ms-excel',
+  xlsx: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
+  ppt: 'application/vnd.ms-powerpoint',
+  pptx: 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
+  odt: 'application/vnd.oasis.opendocument.text',
+  ods: 'application/vnd.oasis.opendocument.spreadsheet',
+  odp: 'application/vnd.oasis.opendocument.presentation',
+  rtf: 'application/rtf',
+  epub: 'application/epub+zip',
+  zip: 'application/zip',
+  '7z': 'application/x-7z-compressed',
+  rar: 'application/vnd.rar',
+  gz: 'application/gzip',
+  tar: 'application/x-tar',
+  apk: 'application/vnd.android.package-archive',
+  txt: 'text/plain',
+  csv: 'text/csv',
+  html: 'text/html',
+  htm: 'text/html',
+  md: 'text/markdown',
+  json: 'application/json',
+  xml: 'application/xml',
+  ics: 'text/calendar',
+  vcf: 'text/vcard',
+  eml: 'message/rfc822',
+  png: 'image/png',
+  jpg: 'image/jpeg',
+  jpeg: 'image/jpeg',
+  gif: 'image/gif',
+  webp: 'image/webp',
+  heic: 'image/heic',
+  heif: 'image/heif',
+  avif: 'image/avif',
+  bmp: 'image/bmp',
+  tif: 'image/tiff',
+  tiff: 'image/tiff',
+  svg: 'image/svg+xml',
+  ico: 'image/x-icon',
+  mp3: 'audio/mpeg',
+  m4a: 'audio/mp4',
+  aac: 'audio/aac',
+  wav: 'audio/wav',
+  ogg: 'audio/ogg',
+  opus: 'audio/ogg',
+  flac: 'audio/flac',
+  amr: 'audio/amr',
+  mp4: 'video/mp4',
+  m4v: 'video/mp4',
+  mov: 'video/quicktime',
+  webm: 'video/webm',
+  mkv: 'video/x-matroska',
+  avi: 'video/x-msvideo',
+  wmv: 'video/x-ms-wmv',
+  '3gp': 'video/3gpp',
+};
+
+/**
+ * The type to hand a file to another app with: the declared one, unless it
+ * is generic or a catch-all that names no format, in which case the one the
+ * file name implies.
+ */
+export function handoffMimeType(name: string | undefined, type: string | null | undefined): string {
+  const declared = baseMime(type);
+  const fromName = EXT_TO_MIME[extension(name || '')];
+  if (!fromName) return type || 'application/octet-stream';
+  if (GENERIC_MIME.has(declared)) return fromName;
+  // An "x-" application type the name contradicts, such as x-as400attachment.
+  if (/^application\/x-/.test(declared) && declared !== fromName) return fromName;
+  return type || fromName;
+}

src/lib/markdown-html.ts

@@ -0,0 +1,280 @@
+// Markdown to HTML for the file preview. Covers what README files and notes
+// use: ATX and setext headings, paragraphs, emphasis, strikethrough, inline
+// and fenced code, block quotes, nested lists and task lists, GFM tables,
+// rules, links, images and autolinks. Every piece of source text is escaped
+// and only http(s)/mailto URLs survive, so the output carries no markup the
+// author wrote; it is still shown through the mail-body sanitiser, which
+// blocks remote images like it does for mail.
+
+const ESCAPES: Record<string, string> = { '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;' };
+
+function escapeHtml(s: string): string {
+  return s.replace(/[&<>"']/g, (ch) => ESCAPES[ch]);
+}
+
+function safeUrl(raw: string): string | null {
+  const url = raw.trim().replace(/^<|>$/g, '');
+  if (/^(https?:|mailto:)/i.test(url)) return url;
+  // Relative links point into a repository the preview doesn't have.
+  return null;
+}
+
+/** Inline markup of one block's text. */
+export function renderInline(src: string): string {
+  // Code spans first: nothing inside them is markup.
+  const codes: string[] = [];
+  let s = src.replace(/(`+)([\s\S]*?[^`])\1(?!`)/g, (_m, _ticks, code: string) => {
+    codes.push(`<code>${escapeHtml(code.trim())}</code>`);
+    return `\u0000${codes.length - 1}\u0000`;
+  });
+  // Backslash escapes.
+  const escaped: string[] = [];
+  s = s.replace(/\\([\\`*_{}[\]()#+\-.!|~>])/g, (_m, ch: string) => {
+    escaped.push(escapeHtml(ch));
+    return `\u0001${escaped.length - 1}\u0001`;
+  });
+  // Links and images, before escaping so the brackets are still there.
+  const links: string[] = [];
+  const stash = (html: string) => {
+    links.push(html);
+    return `\u0002${links.length - 1}\u0002`;
+  };
+  s = s.replace(/!\[([^\]]*)\]\(\s*(<[^>]*>|[^\s)]+)(?:\s+"([^"]*)")?\s*\)/g, (_m, alt: string, url: string, title?: string) => {
+    const href = safeUrl(url);
+    if (!href) return stash(escapeHtml(alt));
+    const t = title ? ` title="${escapeHtml(title)}"` : '';
+    return stash(`<img src="${escapeHtml(href)}" alt="${escapeHtml(alt)}"${t}>`);
+  });
+  s = s.replace(/\[([^\]]+)\]\(\s*(<[^>]*>|[^\s)]+)(?:\s+"([^"]*)")?\s*\)/g, (_m, text: string, url: string, title?: string) => {
+    const href = safeUrl(url);
+    const inner = renderEmphasis(escapeHtml(text));
+    if (!href) return stash(inner);
+    const t = title ? ` title="${escapeHtml(title)}"` : '';
+    return stash(`<a href="${escapeHtml(href)}"${t}>${inner}</a>`);
+  });
+  s = s.replace(/<((?:https?:\/\/|mailto:)[^\s>]+)>/gi, (_m, url: string) => stash(`<a href="${escapeHtml(url)}">${escapeHtml(url)}</a>`));
+  s = s.replace(/(^|[\s(])(https?:\/\/[^\s<>()]+[^\s<>().,;:!?'"])/g, (_m, lead: string, url: string) => (
+    lead + stash(`<a href="${escapeHtml(url)}">${escapeHtml(url)}</a>`)
+  ));
+
+  s = renderEmphasis(escapeHtml(s));
+  // Hard line breaks: two trailing spaces or a backslash.
+  s = s.replace(/ {2,}\n|\\\n/g, '<br>\n');
+
+  return s
+    .replace(/\u0002(\d+)\u0002/g, (_m, i: string) => links[Number(i)])
+    .replace(/\u0001(\d+)\u0001/g, (_m, i: string) => escaped[Number(i)])
+    .replace(/\u0000(\d+)\u0000/g, (_m, i: string) => codes[Number(i)]);
+}
+
+function renderEmphasis(s: string): string {
+  return s
+    .replace(/(\*\*|__)(?=\S)([\s\S]*?\S)\1/g, '<strong>$2</strong>')
+    .replace(/(^|[^\w*])\*(?=\S)([\s\S]*?\S)\*(?!\*)/g, '$1<em>$2</em>')
+    .replace(/(^|[^\w])_(?=\S)([\s\S]*?\S)_(?!\w)/g, '$1<em>$2</em>')
+    .replace(/~~(?=\S)([\s\S]*?\S)~~/g, '<del>$1</del>');
+}
+
+const FENCE = /^ {0,3}(`{3,}|~{3,})\s*([^`\s]*)/;
+const HEADING = /^ {0,3}(#{1,6})(?:[ \t]+(.*?))?(?:[ \t]+#+)?[ \t]*$/;
+const RULE = /^ {0,3}([-*_])(?:[ \t]*\1){2,}[ \t]*$/;
+const LIST_ITEM = /^( *)([-*+]|\d{1,9}[.)])[ \t]+(.*)$/;
+const QUOTE = /^ {0,3}> ?(.*)$/;
+const TABLE_DELIM = /^ *\|? *:?-+:? *(\| *:?-+:? *)*\|? *$/;
+
+function splitRow(line: string): string[] {
+  let row = line.trim();
+  if (row.startsWith('|')) row = row.slice(1);
+  if (row.endsWith('|') && !row.endsWith('\\|')) row = row.slice(0, -1);
+  return row.split(/(?<!\\)\|/).map((cell) => cell.trim().replace(/\\\|/g, '|'));
+}
+
+function isBlockStart(line: string): boolean {
+  return FENCE.test(line) || HEADING.test(line) || RULE.test(line) || QUOTE.test(line) || LIST_ITEM.test(line);
+}
+
+function renderList(lines: string[], start: number): { html: string; next: number } {
+  const first = LIST_ITEM.exec(lines[start])!;
+  const indent = first[1].length;
+  const ordered = /\d/.test(first[2]);
+  const startNum = ordered ? parseInt(first[2], 10) : 1;
+  const items: string[] = [];
+  let i = start;
+  while (i < lines.length) {
+    const m = LIST_ITEM.exec(lines[i]);
+    if (!m || m[1].length !== indent || /\d/.test(m[2]) !== ordered) break;
+    // The item's own lines: continuation text and deeper-indented blocks.
+    const body: string[] = [m[3]];
+    i += 1;
+    while (i < lines.length) {
+      const line = lines[i];
+      if (line.trim() === '') {
+        const nextLine = lines[i + 1];
+        if (nextLine !== undefined && /^\s+/.test(nextLine) && nextLine.search(/\S/) > indent) {
+          body.push('');
+          i += 1;
+          continue;
+        }
+        break;
+      }
+      const sub = LIST_ITEM.exec(line);
+      if (sub && sub[1].length <= indent) break;
+      if (!sub && line.search(/\S/) <= indent && isBlockStart(line)) break;
+      body.push(line.slice(Math.min(line.search(/\S/), indent + 2)));
+      i += 1;
+    }
+    let content = body.join('\n');
+    let task = '';
+    const box = /^\[([ xX])\][ \t]+/.exec(content);
+    if (box) {
+      // A glyph, not an <input>: the mail sanitiser drops form controls.
+      task = box[1] === ' ' ? '☐ ' : '☑ ';
+      content = content.slice(box[0].length);
+    }
+    const inner = renderBlocks(content.split('\n'), true);
+    items.push(`<li${task ? ' class="task"' : ''}>${task}${inner}</li>`);
+    if (lines[i] !== undefined && lines[i].trim() === '') {
+      // A blank line between items keeps the list going.
+      const after = LIST_ITEM.exec(lines[i + 1] ?? '');
+      if (after && after[1].length === indent) i += 1;
+    }
+  }
+  const tag = ordered ? 'ol' : 'ul';
+  const startAttr = ordered && startNum !== 1 ? ` start="${startNum}"` : '';
+  return { html: `<${tag}${startAttr}>${items.join('')}</${tag}>`, next: i };
+}
+
+function renderBlocks(lines: string[], tight = false): string {
+  const out: string[] = [];
+  let i = 0;
+  while (i < lines.length) {
+    const line = lines[i];
+    if (line.trim() === '') { i += 1; continue; }
+
+    const fence = FENCE.exec(line);
+    if (fence) {
+      const marker = fence[1];
+      const code: string[] = [];
+      i += 1;
+      while (i < lines.length && !lines[i].trimStart().startsWith(marker)) {
+        code.push(lines[i]);
+        i += 1;
+      }
+      i += 1;
+      const lang = fence[2] ? ` class="language-${escapeHtml(fence[2])}"` : '';
+      out.push(`<pre><code${lang}>${escapeHtml(code.join('\n'))}</code></pre>`);
+      continue;
+    }
+
+    const heading = HEADING.exec(line);
+    if (heading) {
+      const level = heading[1].length;
+      out.push(`<h${level}>${renderInline(heading[2] ?? '')}</h${level}>`);
+      i += 1;
+      continue;
+    }
+
+    if (RULE.test(line)) {
+      out.push('<hr>');
+      i += 1;
+      continue;
+    }
+
+    if (QUOTE.test(line)) {
+      const quoted: string[] = [];
+      while (i < lines.length && lines[i].trim() !== '') {
+        const q = QUOTE.exec(lines[i]);
+        quoted.push(q ? q[1] : lines[i]);
+        i += 1;
+      }
+      out.push(`<blockquote>${renderBlocks(quoted)}</blockquote>`);
+      continue;
+    }
+
+    if (LIST_ITEM.test(line)) {
+      const list = renderList(lines, i);
+      out.push(list.html);
+      i = list.next;
+      continue;
+    }
+
+    if (/^ {4,}\S/.test(line)) {
+      const code: string[] = [];
+      while (i < lines.length && (/^ {4}/.test(lines[i]) || lines[i].trim() === '')) {
+        code.push(lines[i].slice(4));
+        i += 1;
+      }
+      while (code.length && code[code.length - 1].trim() === '') code.pop();
+      out.push(`<pre><code>${escapeHtml(code.join('\n'))}</code></pre>`);
+      continue;
+    }
+
+    if (line.includes('|') && i + 1 < lines.length && TABLE_DELIM.test(lines[i + 1]) && lines[i + 1].includes('-')) {
+      const head = splitRow(line);
+      const align = splitRow(lines[i + 1]).map((cell) => {
+        const left = cell.startsWith(':');
+        const right = cell.endsWith(':');
+        if (left && right) return 'center';
+        if (right) return 'right';
+        return left ? 'left' : '';
+      });
+      const cell = (tag: string, text: string, col: number) => {
+        const a = align[col] ? ` style="text-align:${align[col]}"` : '';
+        return `<${tag}${a}>${renderInline(text)}</${tag}>`;
+      };
+      const rows: string[] = [];
+      i += 2;
+      while (i < lines.length && lines[i].trim() !== '' && lines[i].includes('|')) {
+        const cells = splitRow(lines[i]);
+        rows.push(`<tr>${head.map((_h, col) => cell('td', cells[col] ?? '', col)).join('')}</tr>`);
+        i += 1;
+      }
+      out.push(`<table><thead><tr>${head.map((h, col) => cell('th', h, col)).join('')}</tr></thead>`
+        + `<tbody>${rows.join('')}</tbody></table>`);
+      continue;
+    }
+
+    // Paragraph: until a blank line or another block; a setext underline
+    // turns it into a heading.
+    const para: string[] = [];
+    while (i < lines.length && lines[i].trim() !== '' && (para.length === 0 || !isBlockStart(lines[i]))) {
+      if (para.length > 0 && /^ {0,3}(=+|-+)[ \t]*$/.test(lines[i])) break;
+      para.push(lines[i]);
+      i += 1;
+    }
+    const setext = i < lines.length ? /^ {0,3}(=+|-+)[ \t]*$/.exec(lines[i]) : null;
+    if (setext && para.length > 0) {
+      const level = setext[1].startsWith('=') ? 1 : 2;
+      out.push(`<h${level}>${renderInline(para.join('\n').trim())}</h${level}>`);
+      i += 1;
+      continue;
+    }
+    const text = renderInline(para.map((l) => l.replace(/^ {1,3}/, '')).join('\n'));
+    // List items keep their text bare, as in a tight list.
+    out.push(tight ? text : `<p>${text}</p>`);
+  }
+  return out.join('\n');
+}
+
+const STYLE = `
+body{font-family:-apple-system,system-ui,Roboto,sans-serif;font-size:15px;line-height:1.55;word-wrap:break-word}
+h1,h2{border-bottom:1px solid rgba(128,128,128,.3);padding-bottom:.25em}
+h1{font-size:1.6em}h2{font-size:1.35em}h3{font-size:1.15em}
+h1,h2,h3,h4,h5,h6{margin:1.1em 0 .5em;line-height:1.25}
+p,ul,ol,blockquote,pre,table{margin:0 0 .9em}
+ul,ol{padding-left:1.6em}li>p{margin:0 0 .4em}li.task{list-style:none;margin-left:-1.3em}
+code{font-family:ui-monospace,Menlo,Consolas,monospace;font-size:.9em;background:rgba(128,128,128,.15);padding:.1em .3em;border-radius:4px}
+pre{background:rgba(128,128,128,.12);padding:.8em;border-radius:6px;overflow-x:auto}
+pre code{background:none;padding:0;font-size:.85em}
+blockquote{margin-left:0;padding-left:1em;border-left:4px solid rgba(128,128,128,.4);color:rgba(128,128,128,1)}
+table{border-collapse:collapse;display:block;overflow-x:auto}
+th,td{border:1px solid rgba(128,128,128,.35);padding:.35em .7em}th{background:rgba(128,128,128,.1)}
+hr{border:0;border-top:1px solid rgba(128,128,128,.35);margin:1.4em 0}
+img{max-width:100%}
+`;
+
+/** A Markdown file as an HTML document for the preview. */
+export function markdownToHtml(markdown: string): string {
+  const lines = markdown.replace(/\r\n?/g, '\n').replace(/\t/g, '    ').split('\n');
+  return `<!doctype html><html><head><meta charset="utf-8"><style>${STYLE}</style></head><body>${renderBlocks(lines)}</body></html>`;
+}

src/lib/pdf-pages.ts

@@ -0,0 +1,67 @@
+// Android's PDF pages for the file preview, rendered by BulwarkPdfModule
+// (the platform's PdfRenderer) into PNGs next to the PDF. iOS needs none of
+// this: its WebView shows PDFs itself.
+
+import { NativeModules, Platform } from 'react-native';
+
+export interface PdfPageSize {
+  /** In points. */
+  width: number;
+  height: number;
+}
+
+interface NativePdf {
+  open(fileUri: string): Promise<{ pages: PdfPageSize[] }>;
+  renderPage(fileUri: string, index: number, width: number, outUri: string): Promise<string>;
+  close(fileUri: string): Promise<void>;
+}
+
+function native(): NativePdf | null {
+  if (Platform.OS !== 'android') return null;
+  return (NativeModules.BulwarkPdf as NativePdf | undefined) ?? null;
+}
+
+/** Whether this build renders PDFs in-app. */
+export function canRenderPdfPages(): boolean {
+  return native() !== null;
+}
+
+export type PdfOpenFailure = 'protected' | 'unreadable';
+
+export class PdfOpenError extends Error {
+  constructor(readonly reason: PdfOpenFailure, message: string) {
+    super(message);
+  }
+}
+
+/** The pages of a PDF, or a {@link PdfOpenError} saying why it can't be shown. */
+export async function openPdfPages(fileUri: string): Promise<PdfPageSize[]> {
+  const pdf = native();
+  if (!pdf) throw new PdfOpenError('unreadable', 'PDF rendering is not available');
+  try {
+    const { pages } = await pdf.open(fileUri);
+    if (!pages.length) throw new PdfOpenError('unreadable', 'The PDF has no pages');
+    return pages;
+  } catch (e) {
+    if (e instanceof PdfOpenError) throw e;
+    const code = (e as { code?: string } | null)?.code;
+    throw new PdfOpenError(code === 'E_PDF_PROTECTED' ? 'protected' : 'unreadable', e instanceof Error ? e.message : String(e));
+  }
+}
+
+/** Render page `index` (0-based) `width` pixels wide into `outUri`. */
+export function renderPdfPage(fileUri: string, index: number, width: number, outUri: string): Promise<string> {
+  const pdf = native();
+  if (!pdf) return Promise.reject(new Error('PDF rendering is not available'));
+  return pdf.renderPage(fileUri, index, Math.round(width), outUri);
+}
+
+/** Let go of the open document. */
+export function closePdfPages(fileUri: string): void {
+  void native()?.close(fileUri).catch(() => undefined);
+}
+
+/** Name of the image a page is rendered into, next to the viewer page. */
+export function pdfPageFileName(index: number): string {
+  return `__page-${index + 1}.png`;
+}

src/lib/preview-viewer-html.ts

@@ -0,0 +1,142 @@
+// The pages the file preview shows images and media in. Each is written next
+// to the downloaded file and loaded from there, so the WebView reads the
+// file by a relative URL and nothing else on the device. They post 'error'
+// when the WebView can't decode the file, so the preview can offer another
+// app instead of a blank page or a dead player.
+
+export interface ViewerColors {
+  /** The app's theme, so the WebView draws its own controls to match. */
+  scheme: 'light' | 'dark';
+  background: string;
+  text: string;
+  textMuted: string;
+  surface: string;
+}
+
+const ESCAPES: Record<string, string> = { '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;' };
+
+function escapeHtml(s: string): string {
+  return s.replace(/[&<>"']/g, (ch) => ESCAPES[ch]);
+}
+
+/** A file name as a relative URL: every reserved character encoded. */
+export function relativeFileUrl(fileName: string): string {
+  return encodeURIComponent(fileName).replace(/[!'()*]/g, (ch) => `%${ch.charCodeAt(0).toString(16).toUpperCase()}`);
+}
+
+const REPORT = `function report(m){try{window.ReactNativeWebView.postMessage(m)}catch(e){}}`;
+
+function page(title: string, colors: ViewerColors, viewport: string, style: string, body: string): string {
+  return '<!doctype html><html><head><meta charset="utf-8">'
+    + `<meta name="viewport" content="${viewport}">`
+    + `<title>${escapeHtml(title)}</title>`
+    + `<style>:root{color-scheme:${colors.scheme}}html,body{margin:0;height:100%;background:${colors.background};color:${colors.text};`
+    + `font-family:-apple-system,system-ui,Roboto,sans-serif;-webkit-user-select:none;user-select:none}${style}</style>`
+    + `</head><body>${body}</body></html>`;
+}
+
+/**
+ * An image fitted to the screen, with the WebView's own pinch zoom. Used on
+ * Android, where React Native's Image can't zoom, and for SVG and ICO, which
+ * it can't draw. SVG is shown through <img>, so its scripts never run and it
+ * loads nothing from the network.
+ */
+export function imageViewerHtml(fileName: string, colors: ViewerColors): string {
+  // Raster icons scaled up stay crisp instead of blurring.
+  const fillClass = /\.(ico|bmp|gif|png)$/i.test(fileName) ? 'fill pixel' : 'fill';
+  return page(
+    fileName,
+    colors,
+    'width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=10,user-scalable=yes',
+    'body{display:flex;align-items:center;justify-content:center;box-sizing:border-box;padding:16px}'
+    + 'img{display:block;max-width:100%;max-height:100%;width:auto;height:auto;object-fit:contain}'
+    // A vector or a tiny icon has no useful natural size; fill the screen.
+    + 'img.fill{width:100%;height:100%}'
+    + 'img.pixel{image-rendering:pixelated}',
+    `<img id="i" alt="${escapeHtml(fileName)}" src="${relativeFileUrl(fileName)}">`
+    + `<script>${REPORT}var i=document.getElementById('i');`
+    + `i.addEventListener('error',function(){report('error')});`
+    + `i.addEventListener('load',function(){var s=Math.min(innerWidth,innerHeight)/3;`
+    + `if(!i.naturalWidth||i.naturalWidth<s&&i.naturalHeight<s){i.className='${fillClass}'}`
+    + `report('loaded')});</script>`,
+  );
+}
+
+/**
+ * The platform's own player for a video or a sound. A video fills the
+ * screen on black, with fullscreen and picture in picture where the WebView
+ * offers them; a sound gets a card with its name. Playback starts at once.
+ */
+export function mediaViewerHtml(kind: 'video' | 'audio', fileName: string, colors: ViewerColors): string {
+  const src = relativeFileUrl(fileName);
+  const script = `<script>${REPORT}var m=document.getElementById('m');`
+    + `function failed(){if(!m.currentSrc||m.error||m.networkState===3)report('error')}`
+    + `m.addEventListener('error',failed,true);`
+    // A file whose container plays but has no track the WebView decodes
+    // reports a 0x0 video; offer another app for that too.
+    + `m.addEventListener('loadedmetadata',function(){if(m.tagName==='VIDEO'&&!m.videoWidth&&!m.duration)report('error');else report('loaded')});`
+    + `</script>`;
+  if (kind === 'video') {
+    return page(
+      fileName,
+      { ...colors, scheme: 'dark', background: '#000' },
+      'width=device-width,initial-scale=1',
+      'body{display:flex;align-items:center;justify-content:center}video{width:100%;height:100%;object-fit:contain;background:#000}',
+      `<video id="m" src="${src}" controls autoplay playsinline preload="auto"></video>${script}`,
+    );
+  }
+  const note = '<svg width="72" height="72" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5" '
+    + 'stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">'
+    + '<circle cx="6" cy="17" r="3"/><circle cx="16" cy="15" r="3"/><path d="M9 17V5l10-2v12"/><path d="M9 9l10-2"/></svg>';
+  return page(
+    fileName,
+    colors,
+    'width=device-width,initial-scale=1',
+    'body{display:flex;align-items:center;justify-content:center;box-sizing:border-box;padding:24px}'
+    + `.card{width:100%;max-width:480px;display:flex;flex-direction:column;align-items:center;gap:20px}`
+    + `.art{width:160px;height:160px;border-radius:24px;background:${colors.surface};color:${colors.textMuted};`
+    + 'display:flex;align-items:center;justify-content:center}'
+    + '.name{font-size:17px;font-weight:600;text-align:center;word-break:break-word}'
+    + 'audio{width:100%}',
+    `<div class="card"><div class="art">${note}</div><div class="name">${escapeHtml(fileName)}</div>`
+    + `<audio id="m" src="${src}" controls autoplay preload="auto"></audio></div>${script}`,
+  );
+}
+
+/**
+ * Android's PDF viewer: one placeholder per page at the page's proportions,
+ * filled with an image the app renders when the page comes near the screen
+ * (it posts `page:<index>` and the app answers by calling
+ * `window.__pdfPage(index, src)`). The WebView zooms the whole document, and a
+ * badge shows the page at the middle of the screen.
+ */
+export function pdfViewerHtml(
+  fileName: string,
+  pages: ReadonlyArray<{ width: number; height: number }>,
+  colors: ViewerColors,
+): string {
+  const sizes = JSON.stringify(pages.map((p) => [Math.max(1, Math.round(p.width)), Math.max(1, Math.round(p.height))]));
+  return page(
+    fileName,
+    { ...colors, background: colors.surface },
+    'width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=6,user-scalable=yes',
+    'body{height:auto;min-height:100%}'
+    + '#doc{padding:8px 8px 56px;display:flex;flex-direction:column;align-items:center;gap:8px}'
+    + '.page{width:100%;max-width:1000px;background:#fff;box-shadow:0 1px 3px rgba(0,0,0,.25);position:relative}'
+    + '.page img{position:absolute;inset:0;width:100%;height:100%;opacity:0;transition:opacity .15s}'
+    + '.page img.on{opacity:1}'
+    + `#badge{position:fixed;left:50%;bottom:16px;transform:translateX(-50%);padding:4px 12px;border-radius:999px;`
+    + `background:rgba(0,0,0,.65);color:#fff;font-size:13px;font-variant-numeric:tabular-nums;transition:opacity .3s}`
+    + '#badge.hide{opacity:0}',
+    '<div id="doc"></div><div id="badge"></div>'
+    + `<script>${REPORT}(function(){var sizes=${sizes},doc=document.getElementById('doc'),badge=document.getElementById('badge'),asked={},els=[];`
+    + `sizes.forEach(function(s,i){var d=document.createElement('div');d.className='page';d.style.aspectRatio=s[0]+'/'+s[1];d.dataset.i=i;`
+    + `var img=document.createElement('img');img.alt='';img.onload=function(){img.className='on'};d.appendChild(img);doc.appendChild(d);els.push(d)});`
+    + `var io=new IntersectionObserver(function(es){es.forEach(function(e){var i=+e.target.dataset.i;if(e.isIntersecting&&!asked[i]){asked[i]=1;report('page:'+i)}})},{rootMargin:'100% 0px'});`
+    + `els.forEach(function(el){io.observe(el)});`
+    + `window.__pdfPage=function(i,src){var img=els[i]&&els[i].firstChild;if(img)img.src=src};`
+    + `var t;function where(){var mid=innerHeight/2,n=1;for(var i=0;i<els.length;i++){var r=els[i].getBoundingClientRect();if(r.top<=mid){n=i+1}else break}`
+    + `badge.textContent=n+' / '+els.length;badge.className='';clearTimeout(t);t=setTimeout(function(){badge.className='hide'},1200)}`
+    + `addEventListener('scroll',where,{passive:true});where();report('loaded')})();</script>`,
+  );
+}

src/lib/zip-preview.ts

@@ -0,0 +1,90 @@
+// ZIP archives in the file preview: the entries as a list, and one entry's
+// bytes when it is opened. Nothing is extracted to disk under the archive's
+// paths; an opened entry goes through the same preview as any attachment.
+
+import type JSZip from 'jszip';
+
+export interface ZipEntry {
+  /** Full path inside the archive, as stored. */
+  path: string;
+  /** Last path segment. */
+  name: string;
+  /** Folder path, '' at the top. */
+  folder: string;
+  /** Uncompressed size, when the archive records it. */
+  size?: number;
+  modified?: Date;
+}
+
+export interface ZipArchive {
+  entries: ZipEntry[];
+  /** True when the listing stopped at {@link MAX_ZIP_ENTRIES}. */
+  truncated: boolean;
+  /** One entry's bytes. */
+  read(path: string): Promise<Uint8Array>;
+}
+
+/** The archive is password-protected; JSZip can't decrypt it. */
+export class ZipEncryptedError extends Error {}
+
+// Metadata the archives of macOS and Windows carry and nobody wants to open.
+const JUNK = /(^|\/)(__MACOSX\/|\.DS_Store$|Thumbs\.db$|desktop\.ini$)/i;
+
+/** Most entries listed; a larger archive lists the first ones. */
+export const MAX_ZIP_ENTRIES = 2000;
+
+// JSZip keeps the directory's sizes here without exposing them.
+interface ZipObjectInternals {
+  _data?: { uncompressedSize?: number };
+}
+
+/**
+ * Read an archive's directory: its files (not folders), sorted by folder and
+ * then name, and a reader for their contents.
+ */
+export async function openZip(bytes: Uint8Array): Promise<ZipArchive> {
+  const { default: Zip } = await import('jszip');
+  let zip: JSZip;
+  try {
+    zip = await Zip.loadAsync(bytes, { createFolders: false });
+  } catch (e) {
+    if (/encrypt/i.test(e instanceof Error ? e.message : String(e))) throw new ZipEncryptedError('encrypted');
+    throw e;
+  }
+  const entries: ZipEntry[] = [];
+  let truncated = false;
+  for (const file of Object.values(zip.files)) {
+    if (file.dir || JUNK.test(file.name)) continue;
+    if (entries.length >= MAX_ZIP_ENTRIES) {
+      truncated = true;
+      break;
+    }
+    const path = file.name;
+    const slash = path.lastIndexOf('/');
+    const size = (file as unknown as ZipObjectInternals)._data?.uncompressedSize;
+    entries.push({
+      path,
+      name: slash >= 0 ? path.slice(slash + 1) : path,
+      folder: slash >= 0 ? path.slice(0, slash) : '',
+      size: typeof size === 'number' && size >= 0 ? size : undefined,
+      modified: file.date instanceof Date && !Number.isNaN(file.date.getTime()) ? file.date : undefined,
+    });
+  }
+  entries.sort((a, b) => a.folder.localeCompare(b.folder) || a.name.localeCompare(b.name));
+  return {
+    entries,
+    truncated,
+    read: async (path) => {
+      const file = zip.file(path);
+      if (!file) throw new Error(`${path} is not in the archive`);
+      return file.async('uint8array');
+    },
+  };
+}
+
+/** Whether a file is a ZIP the preview lists (not one of the formats built on ZIP). */
+export function isZipArchive(name: string, type?: string | null): boolean {
+  const mime = (type || '').split(';')[0].trim().toLowerCase();
+  if (mime === 'application/zip' || mime === 'application/x-zip-compressed' || mime === 'application/x-zip') return true;
+  return /\.zip$/i.test(name);
+}

src/screens/FilesScreen.tsx

@@ -360,8 +360,8 @@ export default function FilesScreen() {
     }
   }, [t]);
 
-  // Tap on a file: the in-app preview for the types it shows (images, text
-  // and code, .eml, PDFs on iOS), the other app for the rest.
+  // Tap on a file: the in-app preview for the types it shows (lib/file-preview),
+  // the other app for the rest.
   const openFile = useCallback((row: FileRow) => {
     if (canPreviewInApp(row)) setPreviewTarget(row);
     else void openFileWith(row);