import Foundation
import os
import Security

/// Ids and steps only, never credentials or message content. Shared by the
/// notification extension and the app's push renewal (PushRenewal.swift).
let pushLog = os.Logger(subsystem: Bundle.main.bundleIdentifier ?? "org.bulwarkmail.mobile", category: "push")

/// Items the app shares with this extension through a keychain access group
/// (BulwarkKeychainGroup in Info.plist). The app writes them with
/// expo-secure-store: generic passwords whose account and generic attributes
/// are the UTF-8 key and whose service is "app:no-auth".
enum SharedKeychain {
  static let service = "app:no-auth"

  static var group: String? {
    Bundle.main.object(forInfoDictionaryKey: "BulwarkKeychainGroup") as? String
  }

  static func read(_ key: String) -> Data? {
    guard let group else { return nil }
    let account = Data(key.utf8)
    let query: [String: Any] = [
      kSecClass as String: kSecClassGenericPassword,
      kSecAttrAccount as String: account,
      kSecAttrAccessGroup as String: group,
      kSecMatchLimit as String: kSecMatchLimitOne,
      kSecReturnData as String: true,
    ]
    var item: CFTypeRef?
    let status = SecItemCopyMatching(query as CFDictionary, &item)
    guard status == errSecSuccess else {
      pushLog.error("keychain read of \(key, privacy: .public) failed: \(status, privacy: .public)")
      return nil
    }
    return item as? Data
  }

  /// SecureStore keys: letters, digits, ".", "-", "_" only. The app builds
  /// the same key part (src/lib/ios-push-shared.ts keyPart).
  static func keyPart(_ id: String) -> String {
    String(id.map { ch in (ch.isASCII && (ch.isLetter || ch.isNumber)) || ch == "." || ch == "-" || ch == "_" ? ch : "_" })
  }

  /// The keys of the shared items whose key starts with `prefix`.
  static func keys(withPrefix prefix: String) -> [String] {
    guard let group else { return [] }
    let query: [String: Any] = [
      kSecClass as String: kSecClassGenericPassword,
      kSecAttrService as String: service,
      kSecAttrAccessGroup as String: group,
      kSecMatchLimit as String: kSecMatchLimitAll,
      kSecReturnAttributes as String: true,
    ]
    var items: CFTypeRef?
    let status = SecItemCopyMatching(query as CFDictionary, &items)
    guard status == errSecSuccess, let list = items as? [[String: Any]] else {
      if status != errSecItemNotFound {
        pushLog.error("keychain listing failed: \(status, privacy: .public)")
      }
      return []
    }
    return list.compactMap { item in
      let account = item[kSecAttrAccount as String]
      let key = (account as? Data).flatMap { String(data: $0, encoding: .utf8) } ?? (account as? String)
      guard let key, key.hasPrefix(prefix) else { return nil }
      return key
    }
  }

  static func readJSON(_ key: String) -> [String: Any]? {
    guard let data = read(key) else { return nil }
    return (try? JSONSerialization.jsonObject(with: data)) as? [String: Any]
  }

  /// Replaces the value of an existing item (refreshed OAuth tokens). Never
  /// creates one: the app owns which items exist.
  @discardableResult
  static func update(_ key: String, json: [String: Any]) -> Bool {
    guard let group, let data = try? JSONSerialization.data(withJSONObject: json) else { return false }
    let account = Data(key.utf8)
    let query: [String: Any] = [
      kSecClass as String: kSecClassGenericPassword,
      kSecAttrService as String: service,
      kSecAttrAccount as String: account,
      kSecAttrAccessGroup as String: group,
    ]
    let attributes: [String: Any] = [kSecValueData as String: data]
    return SecItemUpdate(query as CFDictionary, attributes as CFDictionary) == errSecSuccess
  }
}