import Foundation
import WatchConnectivity
import Combine

/// Bridges data between iOS and watchOS apps
class WatchConnectivityManager: NSObject, ObservableObject {
    
    static let shared = WatchConnectivityManager()
    
    @Published var isReachable = false
    @Published var isWatchPaired = false
    @Published var receivedServers: [ServerConfig] = []
    @Published var transferringIds: Set<String> = []
    @Published var transferredIds: Set<String> = []
    
    /// Per-song transfer progress (0.0 to 1.0)
    @Published var transferProgressMap: [String: Double] = [:]
    /// Song titles for display
    @Published var transferTitleMap: [String: String] = [:]
    
    private var session: WCSession?
    private var activeTransfers: [String: WCSessionFileTransfer] = [:]
    private var progressTimer: Timer?
    
    private override init() {
        super.init()
        #if os(iOS)
        loadWatchSongCache()
        #endif
        if WCSession.isSupported() {
            session = WCSession.default
            session?.delegate = self
            session?.activate()
            wcLog("WCSession supported, activating...")
        } else {
            wcLog("WCSession NOT supported on this device")
        }
    }
    
    private func wcLog(_ msg: String) {
        #if os(iOS)
        DebugLogger.shared.log(msg, category: "Watch")
        #else
        print("[Watch] \(msg)")
        #endif
    }
    
    // MARK: - Send message (both platforms)
    
    func sendMessage(_ message: [String: Any], replyHandler: (([String: Any]) -> Void)? = nil) {
        guard let session = session, session.isReachable else {
            wcLog("sendMessage failed: session not reachable")
            return
        }
        session.sendMessage(message, replyHandler: replyHandler, errorHandler: { [weak self] error in
            self?.wcLog("Message send error: \(error)")
        })
    }
    
    // =========================================================================
    // MARK: - iOS-Only: Sending data TO the watch
    // =========================================================================
    
    #if os(iOS)
    
    func sendServersToWatch(_ servers: [ServerConfig]) {
        guard let session = session, session.isPaired, session.isWatchAppInstalled else {
            wcLog("sendServers: watch not paired/installed")
            return
        }
        
        do {
            let data = try JSONEncoder().encode(servers)
            let dict: [String: Any] = ["servers": data]
            try session.updateApplicationContext(dict)
            wcLog("Sent \(servers.count) servers to watch via applicationContext")
        } catch {
            wcLog("Failed to send servers: \(error)")
        }
    }
    
    func transferSongToWatch(fileURL: URL, metadata: [String: Any]) {
        guard let session = session, session.isPaired, session.isWatchAppInstalled else {
            wcLog("transferFile: watch not available")
            return
        }
        
        let transfer = session.transferFile(fileURL, metadata: metadata)
        wcLog("Started file transfer: \(transfer.file.fileURL.lastPathComponent)")
    }
    
    /// High-level: send a downloaded song to the watch for offline playback.
    /// Always transcodes to MP3 192kbps via the server's stream endpoint for fast transfer.
    @discardableResult
    func sendSongToWatch(_ song: Song) -> Bool {
        wcLog("sendSongToWatch: \(song.title) (id: \(song.id))")
        
        guard let session = session else {
            wcLog("FAIL: WCSession is nil")
            return false
        }
        
        guard session.isPaired, session.isWatchAppInstalled else {
            wcLog("FAIL: Watch not paired or app not installed")
            return false
        }
        
        // Check if local file is already a small MP3 — use it directly
        if let localURL = OfflineManager.shared.localURL(for: song.id),
           FileManager.default.fileExists(atPath: localURL.path) {
            let suffix = (song.suffix ?? "").lowercased()
            let fileSize = (try? FileManager.default.attributesOfItem(atPath: localURL.path)[.size] as? Int64) ?? 0
            let isSmallMP3 = suffix == "mp3" && fileSize < 15_000_000 // < 15MB
            
            if isSmallMP3 {
                wcLog("Local MP3 is small enough (\(ByteCountFormatter.string(fromByteCount: fileSize, countStyle: .file))), sending directly")
                return transferFile(localURL, song: song, suffix: "mp3")
            }
        }
        
        // Otherwise, download a transcoded MP3 192kbps from server
        wcLog("Transcoding to MP3 192kbps via server stream endpoint")
        
        DispatchQueue.main.async {
            self.transferringIds.insert(song.id)
            self.transferProgressMap[song.id] = 0.0
            self.transferTitleMap[song.id] = song.title
        }
        
        guard let streamURL = ServerManager.shared.client.streamURL(
            songId: song.id,
            format: "mp3",
            maxBitRate: 192
        ) else {
            wcLog("FAIL: Could not build stream URL")
            DispatchQueue.main.async {
                self.transferringIds.remove(song.id)
                self.transferProgressMap.removeValue(forKey: song.id)
                self.transferTitleMap.removeValue(forKey: song.id)
            }
            return false
        }
        
        // Download transcoded file to temp, then transfer
        Task {
            do {
                let (data, _) = try await URLSession.shared.data(from: streamURL)
                let tempDir = FileManager.default.temporaryDirectory
                let tempFile = tempDir.appendingPathComponent("watch_\(song.id).mp3")
                try data.write(to: tempFile)
                
                let size = ByteCountFormatter.string(fromByteCount: Int64(data.count), countStyle: .file)
                self.wcLog("Transcoded: \(size) → sending to watch")
                
                await MainActor.run {
                    _ = self.transferFile(tempFile, song: song, suffix: "mp3")
                }
            } catch {
                self.wcLog("FAIL: Transcode download failed: \(error.localizedDescription)")
                await MainActor.run {
                    self.transferringIds.remove(song.id)
                    self.transferProgressMap.removeValue(forKey: song.id)
                    self.transferTitleMap.removeValue(forKey: song.id)
                }
            }
        }
        
        return true
    }
    
    /// Transfer a file to the watch with song metadata
    private func transferFile(_ url: URL, song: Song, suffix: String) -> Bool {
        guard let session = session, session.isPaired, session.isWatchAppInstalled else { return false }
        
        let metadata: [String: Any] = [
            "type": "offlineSong",
            "songId": song.id,
            "id": song.id,
            "title": song.title,
            "artist": song.artist ?? "Unknown",
            "album": song.album ?? "Unknown",
            "duration": song.duration ?? 0,
            "coverArt": song.coverArt ?? "",
            "coverArtId": song.coverArt ?? "",
            "suffix": suffix
        ]
        
        DispatchQueue.main.async {
            self.transferringIds.insert(song.id)
            self.transferProgressMap[song.id] = 0.0
            self.transferTitleMap[song.id] = song.title
        }
        
        let transfer = session.transferFile(url, metadata: metadata)
        activeTransfers[song.id] = transfer
        startProgressPolling()
        
        let fileSize = (try? FileManager.default.attributesOfItem(atPath: url.path)[.size] as? Int64) ?? 0
        wcLog("Transfer initiated: \(url.lastPathComponent) (\(ByteCountFormatter.string(fromByteCount: fileSize, countStyle: .file))) → Watch")
        wcLog("Outstanding transfers: \(session.outstandingFileTransfers.count)")
        return true
    }
    
    /// Poll active transfers for progress updates
    private func startProgressPolling() {
        guard progressTimer == nil else { return }
        progressTimer = Timer.scheduledTimer(withTimeInterval: 0.5, repeats: true) { [weak self] _ in
            guard let self = self else { return }
            var anyActive = false
            for (songId, transfer) in self.activeTransfers {
                let pct = transfer.progress.fractionCompleted
                DispatchQueue.main.async {
                    self.transferProgressMap[songId] = pct
                }
                if !transfer.progress.isFinished {
                    anyActive = true
                }
            }
            if !anyActive {
                self.progressTimer?.invalidate()
                self.progressTimer = nil
            }
        }
    }
    
    var isWatchAvailable: Bool {
        isWatchPaired
    }
    
    /// Cancel a specific pending transfer
    func cancelTransfer(songId: String) {
        if let transfer = activeTransfers[songId] {
            transfer.cancel()
            activeTransfers.removeValue(forKey: songId)
            wcLog("Cancelled transfer for: \(transferTitleMap[songId] ?? songId)")
        }
        DispatchQueue.main.async {
            self.transferringIds.remove(songId)
            self.transferProgressMap.removeValue(forKey: songId)
            self.transferTitleMap.removeValue(forKey: songId)
        }
    }
    
    /// Cancel all pending transfers
    func cancelAllTransfers() {
        for (_, transfer) in activeTransfers {
            transfer.cancel()
        }
        activeTransfers.removeAll()
        wcLog("Cancelled all transfers")
        DispatchQueue.main.async {
            self.transferringIds.removeAll()
            self.transferProgressMap.removeAll()
            self.transferTitleMap.removeAll()
        }
    }
    
    /// Ordered list of pending transfer song IDs (for display)
    var pendingTransferList: [(id: String, title: String, progress: Double)] {
        transferringIds.map { id in
            (id: id, title: transferTitleMap[id] ?? id, progress: transferProgressMap[id] ?? 0)
        }.sorted { $0.title < $1.title }
    }
    
    /// Request the watch's song catalog
    @Published var watchSongs: [WatchSongInfo] = []
    @Published var isLoadingWatchSongs = false
    
    /// Cached set of song IDs on the watch — persists across disconnects
    @Published var watchSongIds: Set<String> = []
    
    struct WatchSongInfo: Identifiable, Codable {
        let id: String
        let title: String
        let artist: String
        let album: String
        let fileSize: Int64
    }
    
    /// Check if a song is on the watch (uses cached data)
    func isSongOnWatch(_ songId: String) -> Bool {
        watchSongIds.contains(songId)
    }
    
    /// Persist watch song IDs to UserDefaults
    private func saveWatchSongCache() {
        let ids = Array(watchSongIds)
        UserDefaults.standard.set(ids, forKey: "cached_watch_song_ids")
        if let data = try? JSONEncoder().encode(watchSongs) {
            UserDefaults.standard.set(data, forKey: "cached_watch_songs")
        }
    }
    
    /// Load cached watch song data from UserDefaults
    private func loadWatchSongCache() {
        if let ids = UserDefaults.standard.stringArray(forKey: "cached_watch_song_ids") {
            watchSongIds = Set(ids)
        }
        if let data = UserDefaults.standard.data(forKey: "cached_watch_songs"),
           let songs = try? JSONDecoder().decode([WatchSongInfo].self, from: data) {
            watchSongs = songs
        }
    }
    
    func requestWatchSongList() {
        guard let session = session, session.isReachable else {
            wcLog("requestWatchSongList: watch not reachable")
            return
        }
        isLoadingWatchSongs = true
        session.sendMessage(["type": "requestSongList"], replyHandler: { [weak self] reply in
            if let data = reply["songs"] as? Data,
               let songs = try? JSONDecoder().decode([WatchSongInfo].self, from: data) {
                DispatchQueue.main.async {
                    self?.watchSongs = songs
                    self?.watchSongIds = Set(songs.map { $0.id })
                    self?.isLoadingWatchSongs = false
                    self?.saveWatchSongCache()
                    self?.wcLog("Received \(songs.count) songs from watch")
                }
            } else {
                DispatchQueue.main.async {
                    self?.isLoadingWatchSongs = false
                }
            }
        }, errorHandler: { [weak self] error in
            DispatchQueue.main.async {
                self?.isLoadingWatchSongs = false
                self?.wcLog("requestSongList failed: \(error.localizedDescription)")
            }
        })
    }
    
    /// Request the watch to delete a song
    func requestWatchDeleteSong(_ songId: String) {
        guard let session = session, session.isReachable else { return }
        session.sendMessage(["type": "deleteSong", "songId": songId], replyHandler: { [weak self] _ in
            DispatchQueue.main.async {
                self?.watchSongs.removeAll { $0.id == songId }
                self?.watchSongIds.remove(songId)
                self?.saveWatchSongCache()
                self?.wcLog("Watch deleted: \(songId)")
            }
        }, errorHandler: { error in
            print("Delete song failed: \(error)")
        })
    }
    
    /// Request the watch to delete all songs
    func requestWatchDeleteAll() {
        guard let session = session, session.isReachable else { return }
        session.sendMessage(["type": "deleteAllSongs"], replyHandler: { [weak self] _ in
            DispatchQueue.main.async {
                self?.watchSongs.removeAll()
                self?.watchSongIds.removeAll()
                self?.saveWatchSongCache()
                self?.wcLog("Watch deleted all songs")
            }
        }, errorHandler: nil)
    }
    
    /// Try to wake the watch app by sending a user info transfer
    /// This queues up and is delivered when the watch app launches
    func pingWatch() {
        guard let session = session, session.isPaired, session.isWatchAppInstalled else {
            wcLog("pingWatch: watch not available")
            return
        }
        
        // transferUserInfo is queued and delivered even if watch app is not running
        session.transferUserInfo(["type": "wake", "timestamp": Date().timeIntervalSince1970])
        wcLog("pingWatch: sent wake signal. isReachable: \(session.isReachable)")
        
        if session.isReachable {
            wcLog("pingWatch: watch app is already running")
        } else {
            wcLog("pingWatch: watch app not running — transfer will queue")
        }
    }
    
    /// Returns a summary of watch connectivity state for debugging
    var watchStatusDescription: String {
        guard let session = session else { return "WCSession not supported" }
        var parts: [String] = []
        parts.append("Paired: \(session.isPaired)")
        parts.append("App installed: \(session.isWatchAppInstalled)")
        parts.append("Reachable: \(session.isReachable)")
        parts.append("Activation: \(session.activationState.rawValue)")
        parts.append("Outstanding: \(session.outstandingFileTransfers.count)")
        return parts.joined(separator: " · ")
    }
    
    func sendNowPlayingToWatch(song: Song?, isPlaying: Bool, currentTime: TimeInterval, duration: TimeInterval) {
        guard let session = session, session.isReachable else { return }
        
        var info: [String: Any] = [
            "type": "nowPlaying",
            "isPlaying": isPlaying,
            "currentTime": currentTime,
            "duration": duration
        ]
        
        if let song = song {
            info["songId"] = song.id
            info["title"] = song.title
            info["artist"] = song.artist ?? ""
            info["album"] = song.album ?? ""
            info["coverArtId"] = song.coverArt ?? ""
        }
        
        session.sendMessage(info, replyHandler: nil, errorHandler: nil)
    }
    
    func syncOfflineSongsToWatch(songs: [DownloadedSong]) {
        guard let session = session, session.isPaired, session.isWatchAppInstalled else { return }
        
        do {
            let catalogData = try JSONEncoder().encode(songs.map { $0.song })
            try session.updateApplicationContext([
                "offlineCatalog": catalogData,
                "songCount": songs.count
            ])
        } catch {
            print("Failed to send catalog: \(error)")
        }
        
        for downloaded in songs {
            let fileURL = URL(fileURLWithPath: downloaded.localPath)
            guard FileManager.default.fileExists(atPath: fileURL.path) else { continue }
            
            let metadata: [String: Any] = [
                "songId": downloaded.song.id,
                "title": downloaded.song.title,
                "artist": downloaded.song.artist ?? "",
                "album": downloaded.song.album ?? "",
                "coverArtId": downloaded.song.coverArt ?? "",
                "duration": downloaded.song.duration ?? 0,
                "suffix": downloaded.song.suffix ?? "mp3"
            ]
            
            transferSongToWatch(fileURL: fileURL, metadata: metadata)
        }
    }
    
    #endif
}

// MARK: - WCSessionDelegate
extension WatchConnectivityManager: WCSessionDelegate {
    
    func session(_ session: WCSession, activationDidCompleteWith activationState: WCSessionActivationState, error: Error?) {
        let stateNames = ["notActivated", "inactive", "activated"]
        let stateName = activationState.rawValue < stateNames.count ? stateNames[Int(activationState.rawValue)] : "unknown"
        wcLog("Activation complete: \(stateName), error: \(error?.localizedDescription ?? "none")")
        #if os(iOS)
        wcLog("isPaired: \(session.isPaired), isWatchAppInstalled: \(session.isWatchAppInstalled), isReachable: \(session.isReachable)")
        #endif
        DispatchQueue.main.async {
            self.isReachable = session.isReachable
            #if os(iOS)
            self.isWatchPaired = session.isPaired && session.isWatchAppInstalled
            #endif
        }
        #if os(iOS)
        if activationState == .activated {
            sendServersToWatch(ServerManager.shared.servers)
        }
        #endif
    }
    
    func sessionReachabilityDidChange(_ session: WCSession) {
        wcLog("Reachability changed: \(session.isReachable)")
        DispatchQueue.main.async {
            self.isReachable = session.isReachable
        }
    }
    
    // These two delegate methods are REQUIRED on iOS but do not exist on watchOS
    #if os(iOS)
    func sessionDidBecomeInactive(_ session: WCSession) { }
    func sessionDidDeactivate(_ session: WCSession) {
        session.activate()
    }
    #endif
    
    // MARK: - Receive messages
    
    func session(_ session: WCSession, didReceiveMessage message: [String: Any], replyHandler: @escaping ([String: Any]) -> Void) {
        guard let type = message["type"] as? String else {
            replyHandler(["error": "unknown message type"])
            return
        }
        
        #if os(iOS)
        // iOS handles commands from watch
        switch type {
        case "requestServers":
            do {
                let data = try JSONEncoder().encode(ServerManager.shared.servers)
                replyHandler(["servers": data])
            } catch {
                replyHandler(["error": error.localizedDescription])
            }
            
        case "playCommand":
            DispatchQueue.main.async {
                AudioPlayer.shared.togglePlayPause()
                replyHandler(["isPlaying": AudioPlayer.shared.isPlaying])
            }
            
        case "nextCommand":
            DispatchQueue.main.async {
                AudioPlayer.shared.next()
                replyHandler(["success": true])
            }
            
        case "previousCommand":
            DispatchQueue.main.async {
                AudioPlayer.shared.previous()
                replyHandler(["success": true])
            }
            
        case "requestDownload":
            if let songId = message["songId"] as? String {
                Task {
                    do {
                        let client = ServerManager.shared.client
                        if let song = try await client.getSong(id: songId),
                           let server = ServerManager.shared.activeServer {
                            OfflineManager.shared.downloadSong(song, server: server)
                            replyHandler(["status": "downloading"])
                        } else {
                            replyHandler(["error": "Song not found"])
                        }
                    } catch {
                        replyHandler(["error": error.localizedDescription])
                    }
                }
            }
            
        default:
            replyHandler(["error": "unhandled type: \(type)"])
        }
        
        #else
        // watchOS handles messages from iPhone
        replyHandler(["error": "unhandled on watchOS: \(type)"])
        #endif
    }
    
    // Receive application context
    func session(_ session: WCSession, didReceiveApplicationContext applicationContext: [String: Any]) {
        if let data = applicationContext["servers"] as? Data,
           let servers = try? JSONDecoder().decode([ServerConfig].self, from: data) {
            DispatchQueue.main.async {
                self.receivedServers = servers
            }
        }
    }
    
    // Receive file transfers — watchOS saves songs for offline playback
    func session(_ session: WCSession, didReceive file: WCSessionFile) {
        #if os(watchOS)
        guard let metadata = file.metadata,
              let songId = metadata["id"] as? String,
              let suffix = metadata["suffix"] as? String else {
            print("Received file without proper metadata")
            return
        }
        
        let fm = FileManager.default
        let docs = fm.urls(for: .documentDirectory, in: .userDomainMask).first!
        let musicDir = docs.appendingPathComponent("OfflineMusic", isDirectory: true)
        try? fm.createDirectory(at: musicDir, withIntermediateDirectories: true)
        
        let destURL = musicDir.appendingPathComponent("\(songId).\(suffix)")
        
        // Remove existing if re-transferring
        try? fm.removeItem(at: destURL)
        
        do {
            try fm.moveItem(at: file.fileURL, to: destURL)
            print("Saved offline song: \(songId) to \(destURL.lastPathComponent)")
            
            // Save metadata catalog
            var catalog = loadWatchCatalog()
            catalog[songId] = metadata
            saveWatchCatalog(catalog)
        } catch {
            print("Failed to save transferred file: \(error)")
        }
        #endif
    }
    
    #if os(watchOS)
    private var watchCatalogURL: URL {
        let docs = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
        return docs.appendingPathComponent("watchOfflineCatalog.json")
    }
    
    func loadWatchCatalog() -> [String: [String: Any]] {
        guard let data = try? Data(contentsOf: watchCatalogURL),
              let dict = try? JSONSerialization.jsonObject(with: data) as? [String: [String: Any]] else {
            return [:]
        }
        return dict
    }
    
    private func saveWatchCatalog(_ catalog: [String: [String: Any]]) {
        if let data = try? JSONSerialization.data(withJSONObject: catalog) {
            try? data.write(to: watchCatalogURL)
        }
    }
    
    func watchOfflineSongs() -> [(id: String, title: String, artist: String, album: String, duration: Int, suffix: String)] {
        let catalog = loadWatchCatalog()
        let musicDir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
            .appendingPathComponent("OfflineMusic", isDirectory: true)
        
        return catalog.compactMap { id, meta in
            let suffix = meta["suffix"] as? String ?? "mp3"
            let url = musicDir.appendingPathComponent("\(id).\(suffix)")
            guard FileManager.default.fileExists(atPath: url.path) else { return nil }
            return (
                id: id,
                title: meta["title"] as? String ?? "Unknown",
                artist: meta["artist"] as? String ?? "Unknown",
                album: meta["album"] as? String ?? "Unknown",
                duration: meta["duration"] as? Int ?? 0,
                suffix: suffix
            )
        }.sorted { $0.title < $1.title }
    }
    
    func watchOfflineURL(for songId: String) -> URL? {
        let catalog = loadWatchCatalog()
        guard let meta = catalog[songId] else { return nil }
        let suffix = meta["suffix"] as? String ?? "mp3"
        let musicDir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
            .appendingPathComponent("OfflineMusic", isDirectory: true)
        let url = musicDir.appendingPathComponent("\(songId).\(suffix)")
        return FileManager.default.fileExists(atPath: url.path) ? url : nil
    }
    #endif
    
    // File transfer completion — iOS only
    #if os(iOS)
    func session(_ session: WCSession, didFinish fileTransfer: WCSessionFileTransfer, error: Error?) {
        let songId = fileTransfer.file.metadata?["id"] as? String
        let title = fileTransfer.file.metadata?["title"] as? String ?? "unknown"
        
        if let id = songId {
            activeTransfers.removeValue(forKey: id)
        }
        
        DispatchQueue.main.async {
            if let id = songId {
                self.transferringIds.remove(id)
                self.transferProgressMap.removeValue(forKey: id)
                self.transferTitleMap.removeValue(forKey: id)
                if error == nil {
                    self.transferredIds.insert(id)
                    self.watchSongIds.insert(id)
                    self.saveWatchSongCache()
                }
            }
        }
        if let error = error {
            wcLog("Transfer FAILED for '\(title)': \(error.localizedDescription)")
        } else {
            wcLog("Transfer COMPLETE: '\(title)' (\(fileTransfer.file.fileURL.lastPathComponent))")
            wcLog("Remaining outstanding transfers: \(session.outstandingFileTransfers.count)")
        }
    }
    #endif
}