//! Web views: a view or custom editor whose UI is a web page shipped in the
//! package (`web = "web/index.html"`) instead of content the plugin's code
//! renders.
//!
//! The entry's directory is the page's root. Every file under it is part of
//! the declaration: it is checked when the package is prepared (count, size,
//! no links leaving the package), copied on install and covered by the
//! package digest and signature. The client loads the page in a sandboxed
//! frame (an opaque origin with no network and no IDE API) and fetches its
//! files through [`PluginHost::web_file`] (the desktop's `openidea-plugin`
//! URL scheme); the page talks to the IDE only through the frame bridge.

use super::PluginHost;
use ide_core::{IdeError, IdeResult};
use ide_extension::{Package, check_relative};
use serde::{Deserialize, Serialize};
use specta::Type;
use std::path::{Component, Path, PathBuf};

/// Most files under one web root.
const MAX_FILES: usize = 4096;
/// Most bytes under one web root.
const MAX_BYTES: u64 = 256 << 20;
/// Deepest directory nesting under a web root.
const MAX_DEPTH: usize = 16;

/// Checks a declaration's `web` entry: an `.html` file inside a directory of
/// the package (the directory is what the page can load, so it can't be the
/// package root), and everything under that directory. Returns those files,
/// package-relative.
pub(super) fn web_files(pkg: &Package, entry: &str, what: &str) -> Result<Vec<PathBuf>, String> {
    let path = Path::new(entry);
    check_relative(path, "web")?;
    if entry.contains('\\') || !entry.to_ascii_lowercase().ends_with(".html") {
        return Err(format!("{what}: `web` names an .html file, `/`-separated ({entry:?})"));
    }
    let dir = path.parent().filter(|d| !d.as_os_str().is_empty()).ok_or_else(|| {
        format!("{what}: put the page in a directory of its own (`web/index.html`): the directory is what it can load")
    })?;
    let real_entry = pkg.resolve(path)?;
    if !real_entry.is_file() {
        return Err(format!("{what}: {entry} is not a file"));
    }
    let root = pkg.resolve(dir)?;
    let mut files = Vec::new();
    let mut total = 0u64;
    let mut stack = vec![(root.clone(), dir.to_path_buf(), 0usize)];
    while let Some((real, rel, depth)) = stack.pop() {
        let mut entries: Vec<_> =
            std::fs::read_dir(&real).map_err(|e| format!("{}: {e}", rel.display()))?.filter_map(Result::ok).collect();
        entries.sort_by_key(|e| e.file_name());
        for e in entries {
            let name = e.file_name();
            let rel = rel.join(&name);
            // Links could point anywhere: only what is really in the package counts.
            let ty = e.file_type().map_err(|err| format!("{}: {err}", rel.display()))?;
            if ty.is_symlink() {
                return Err(format!("{what}: {} is a link; web files must be real files", rel.display()));
            }
            if ty.is_dir() {
                if depth + 1 > MAX_DEPTH {
                    return Err(format!("{what}: {} is nested deeper than {MAX_DEPTH} directories", rel.display()));
                }
                stack.push((e.path(), rel, depth + 1));
                continue;
            }
            if name.to_string_lossy() == ".DS_Store" {
                continue;
            }
            let len = e.metadata().map_err(|err| format!("{}: {err}", rel.display()))?.len();
            if len > ide_extension::MAX_PACKAGE_FILE {
                return Err(format!(
                    "{what}: {} is larger than {} MiB",
                    rel.display(),
                    ide_extension::MAX_PACKAGE_FILE >> 20
                ));
            }
            total += len;
            files.push(rel);
            if files.len() > MAX_FILES || total > MAX_BYTES {
                return Err(format!(
                    "{what}: {} holds more than {MAX_FILES} files or {} MiB",
                    dir.display(),
                    MAX_BYTES >> 20
                ));
            }
        }
    }
    files.sort();
    Ok(files)
}

/// The page of a web view, for the client to load in its frame.
#[derive(Clone, Debug, Serialize, Deserialize, Type)]
#[serde(rename_all = "camelCase")]
pub struct WebPage {
    /// `<plugin id>/<revision>/<entry>` under the `openidea-plugin` scheme. The
    /// revision changes with the installed package, so a cached file is never
    /// stale; relative URLs in the page resolve to the package's files.
    pub path: String,
}

/// A file of a web view.
pub struct WebFile {
    pub bytes: Vec<u8>,
    pub mime: &'static str,
}

impl PluginHost {
    /// The web roots `plugin` declares (entry directories, package-relative, `/`-terminated).
    fn web_dirs(&self, plugin: &str) -> Vec<String> {
        [super::ui_points::VIEWS, super::ui_points::CUSTOM_EDITORS]
            .iter()
            .flat_map(|point| self.ui.items(point, Some(plugin)))
            .filter_map(|item| item.decl.get("web").and_then(|w| w.as_str()).map(str::to_owned))
            .filter_map(|entry| entry.rsplit_once('/').map(|(dir, _)| format!("{dir}/")))
            .collect()
    }

    /// Changes whenever the installed package does (cache key of its web files).
    fn web_revision(&self, plugin: &super::LoadedPlugin) -> String {
        let digest = plugin.pkg.digest.as_deref().unwrap_or_default();
        let short: String = digest.chars().filter(char::is_ascii_alphanumeric).take(16).collect();
        if short.is_empty() { format!("v{}", plugin.pkg.manifest.version) } else { short }
    }

    /// The page of `plugin`'s view or custom editor `view`.
    pub fn web_page(&self, plugin_id: &str, view: &str) -> IdeResult<WebPage> {
        let plugin = self.get(plugin_id)?;
        if !plugin.status().is_live() {
            return Err(IdeError::unavailable(format!("plugin {plugin_id:?} is not enabled")));
        }
        let entry = [super::ui_points::VIEWS, super::ui_points::CUSTOM_EDITORS]
            .iter()
            .flat_map(|point| self.ui.items(point, Some(plugin_id)))
            .find(|item| item.key == view)
            .and_then(|item| item.decl.get("web").and_then(|w| w.as_str()).map(str::to_owned))
            .ok_or_else(|| IdeError::not_found(format!("plugin {plugin_id:?} has no web view {view:?}")))?;
        Ok(WebPage { path: format!("{plugin_id}/{}/{entry}", self.web_revision(&plugin)) })
    }

    /// A file of one of `plugin`'s web views: `path` is `<revision>/<package path>`
    /// as [`WebPage::path`] makes them. Only files under a declared web root
    /// of a live plugin are served; the revision must be the installed one.
    pub fn web_file(&self, plugin_id: &str, path: &str) -> IdeResult<WebFile> {
        let plugin = self.get(plugin_id)?;
        if !plugin.status().is_live() {
            return Err(IdeError::unavailable(format!("plugin {plugin_id:?} is not enabled")));
        }
        let (revision, rel) = path.split_once('/').ok_or_else(|| IdeError::not_found(path.to_owned()))?;
        if revision != self.web_revision(&plugin) {
            return Err(IdeError::not_found(format!("{path}: not the installed version")));
        }
        let rel_path = Path::new(rel);
        if !rel_path.components().all(|c| matches!(c, Component::Normal(_))) {
            return Err(IdeError::invalid(format!("{rel}: not a plain relative path")));
        }
        if !self.web_dirs(plugin_id).iter().any(|dir| rel.starts_with(dir.as_str())) {
            return Err(IdeError::not_found(format!("{rel}: not part of a web view")));
        }
        let bytes = plugin.pkg.read_bytes(rel_path).map_err(IdeError::not_found)?;
        Ok(WebFile { bytes, mime: mime(rel) })
    }
}

/// Content type by extension; unknown files are opaque bytes (never sniffed as script).
pub fn mime(path: &str) -> &'static str {
    let ext = path.rsplit_once('.').map(|(_, e)| e.to_ascii_lowercase()).unwrap_or_default();
    match ext.as_str() {
        "html" | "htm" => "text/html; charset=utf-8",
        "js" | "mjs" | "cjs" => "text/javascript; charset=utf-8",
        "css" => "text/css; charset=utf-8",
        "json" | "map" => "application/json",
        "wasm" => "application/wasm",
        "svg" => "image/svg+xml",
        "png" => "image/png",
        "jpg" | "jpeg" => "image/jpeg",
        "gif" => "image/gif",
        "webp" => "image/webp",
        "avif" => "image/avif",
        "ico" => "image/x-icon",
        "woff2" => "font/woff2",
        "woff" => "font/woff",
        "ttf" => "font/ttf",
        "otf" => "font/otf",
        "txt" | "md" => "text/plain; charset=utf-8",
        "mp3" => "audio/mpeg",
        "mp4" => "video/mp4",
        "webm" => "video/webm",
        _ => "application/octet-stream",
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use ide_extension::Manifest;

    fn pkg(dir: &Path) -> Package {
        let src = "id = \"p\"\nname = \"P\"\nversion = \"1.0.0\"\nengines.openidea = \"^1.0\"\n";
        Package::new(Manifest::parse(src).unwrap(), dir.to_path_buf())
    }

    #[test]
    fn a_web_root_is_its_directory_and_nothing_else() {
        let tmp = tempfile::tempdir().unwrap();
        let d = tmp.path();
        std::fs::create_dir_all(d.join("web/assets/fonts")).unwrap();
        std::fs::write(d.join("web/index.html"), "<p>hi</p>").unwrap();
        std::fs::write(d.join("web/assets/app.js"), "1").unwrap();
        std::fs::write(d.join("web/assets/fonts/a.woff2"), "f").unwrap();
        std::fs::write(d.join("web/.DS_Store"), "x").unwrap();
        std::fs::write(d.join("secret.txt"), "no").unwrap();
        let files = web_files(&pkg(d), "web/index.html", "v").unwrap();
        let files: Vec<String> = files.iter().map(|f| f.to_string_lossy().replace('\\', "/")).collect();
        assert_eq!(files, ["web/assets/app.js", "web/assets/fonts/a.woff2", "web/index.html"]);

        std::fs::write(d.join("index.html"), "x").unwrap();
        let err = |entry: &str| web_files(&pkg(d), entry, "v").err().unwrap_or_default();
        assert!(err("index.html").contains("directory of its own"), "{}", err("index.html"));
        assert!(err("web/app.js").contains(".html"));
        assert!(err("../web/index.html").contains("relative"));
        assert!(err("web/missing.html").contains("no such file"));
    }

    #[cfg(unix)]
    #[test]
    fn links_out_of_a_web_root_are_refused() {
        let tmp = tempfile::tempdir().unwrap();
        let d = tmp.path();
        std::fs::create_dir_all(d.join("web")).unwrap();
        std::fs::write(d.join("web/index.html"), "x").unwrap();
        std::os::unix::fs::symlink("/etc/hosts", d.join("web/hosts")).unwrap();
        assert!(web_files(&pkg(d), "web/index.html", "v").unwrap_err().contains("is a link"));
    }

    #[test]
    fn content_types_never_make_unknown_files_scripts() {
        assert_eq!(mime("a/b.JS"), "text/javascript; charset=utf-8");
        assert_eq!(mime("x.woff2"), "font/woff2");
        assert_eq!(mime("x.wasm"), "application/wasm");
        assert_eq!(mime("x.bin"), "application/octet-stream");
        assert_eq!(mime("noext"), "application/octet-stream");
    }
}