import AppKit

@MainActor
protocol WallpaperManaging {
  func download(from url: URL) async throws -> URL
  func setDesktopImage(from fileURL: URL, screen: NSScreen?) throws
  func saveToFolder(from sourceURL: URL, to folderURL: URL) throws
}

@MainActor
protocol DesktopImageSetting {
  func setDesktopImageURL(
    _ url: URL, for screen: NSScreen, options: [NSWorkspace.DesktopImageOptionKey: Any]
  ) throws
}

extension NSWorkspace: DesktopImageSetting {}

class WallpaperManager: WallpaperManaging {
  static let shared = WallpaperManager()

  private let session: URLSession
  private let desktopSetter: @MainActor (URL, NSScreen) throws -> Void

  init(
    session: URLSession = .shared,
    desktopSetter: (@MainActor (URL, NSScreen) throws -> Void)? = nil,
    workspace: DesktopImageSetting = NSWorkspace.shared
  ) {
    self.session = session
    self.desktopSetter =
      desktopSetter ?? { url, screen in
        try workspace.setDesktopImageURL(
          url, for: screen, options: [:]
        )
      }
  }

  /// Downloads the file to a temporary location and returns the local URL.
  func download(from url: URL) async throws -> URL {
    let (data, response) = try await session.data(from: url)
    guard let response = response as? HTTPURLResponse,
      (200...299).contains(response.statusCode)
    else {
      throw WallhavenError.apiError("Wallpaper download failed")
    }

    let filename = url.lastPathComponent
    let tempDir = FileManager.default.temporaryDirectory
    let fileURL = tempDir.appendingPathComponent(filename)

    try data.write(to: fileURL)
    return fileURL
  }

  /// Sets the desktop image from a local file URL.
  @MainActor
  func setDesktopImage(from fileURL: URL, screen: NSScreen? = nil) throws {
    if let screen = screen {
      try desktopSetter(fileURL, screen)
    } else {
      // Set for all screens or just main? Let's default to main for safety,
      // but the UI will likely drive this.
      // If no screen specified, maybe set for the 'active' one.
      let targetScreen = NSScreen.main ?? NSScreen.screens.first!
      try desktopSetter(fileURL, targetScreen)
    }
  }

  /// Copies the file to the specified destination directory.
  func saveToFolder(from sourceURL: URL, to folderURL: URL) throws {
    // Ensure folder exists
    try FileManager.default.createDirectory(at: folderURL, withIntermediateDirectories: true)

    let destinationURL = folderURL.appendingPathComponent(sourceURL.lastPathComponent)

    // If file exists, maybe don't overwrite or handle gracefully?
    // For now, we'll remove it if it exists to ensure we have the fresh one, or just skip.
    if FileManager.default.fileExists(atPath: destinationURL.path) {
      try FileManager.default.removeItem(at: destinationURL)
    }

    try FileManager.default.copyItem(at: sourceURL, to: destinationURL)
  }

  // Legacy support wrapper (optional, but cleaner to update call sites)
  @MainActor
  func setWallpaper(from url: URL, screen: NSScreen? = nil) async throws {
    let localURL = try await download(from: url)
    try setDesktopImage(from: localURL, screen: screen)
  }
}