import Foundation
import AVFoundation
import Combine
import WatchKit
import MediaPlayer
import HealthKit

/// watchOS audio player with dual-mode output:
///
/// **Bluetooth Mode** (default):
///   Uses `.longFormAudio` policy. Requires Bluetooth/AirPlay. Background playback is
///   handled by the audio session itself.
///
/// **Speaker Mode** (Watch Ultra):
///   Uses `.default` policy which routes to the built-in speaker. Background runtime is
///   maintained by a silent `HKWorkoutSession`. watchOS keeps workout apps alive indefinitely
///   even when the screen sleeps. A green workout indicator appears on the watch face.
///
/// Toggle between modes in the Now Playing route indicator.
class WatchAudioPlayer: NSObject, ObservableObject {
    
    static let shared = WatchAudioPlayer()
    
    // MARK: - Published State
    @Published var currentSong: Song?
    @Published var queue: [Song] = []
    @Published var queueIndex: Int = 0
    @Published var isPlaying = false
    @Published var currentTime: TimeInterval = 0
    @Published var duration: TimeInterval = 0
    @Published var volume: Float = 1.0
    @Published var repeatMode: RepeatMode = .off
    @Published var shuffleEnabled = false
    @Published var audioLevels: [Float] = Array(repeating: 0, count: 8)
    
    // Audio route state
    @Published var isSessionActive = false
    @Published var isBluetoothConnected = false
    @Published var currentRouteName: String = "No Output"
    @Published var activationError: String?
    @Published var useSpeakerMode = false {
        didSet {
            UserDefaults.standard.set(useSpeakerMode, forKey: "watch_speaker_mode")
            reconfigureAudioSession()
        }
    }
    @Published var isSpeakerAvailable = false
    
    enum RepeatMode {
        case off, all, one
    }
    
    // MARK: - Private
    private var player: AVPlayer?
    private var playerItem: AVPlayerItem?
    private var timeObserver: Any?
    private var levelTimer: Timer?
    private var pendingPlayURL: URL?
    private var pendingSong: Song?
    
    // HealthKit workout session for speaker background runtime
    private let healthStore = HKHealthStore()
    private var workoutSession: HKWorkoutSession?
    private var workoutBuilder: HKLiveWorkoutBuilder?
    
    private override init() {
        super.init()
        useSpeakerMode = UserDefaults.standard.bool(forKey: "watch_speaker_mode")
        isSpeakerAvailable = checkSpeakerAvailable()
        configureAudioSession()
        setupRemoteControls()
        observeRouteChanges()
    }
    
    // MARK: - Speaker Detection
    
    private func checkSpeakerAvailable() -> Bool {
        // Check if device has a speaker by looking at available outputs
        let route = AVAudioSession.sharedInstance().currentRoute
        let hasBuiltIn = route.outputs.contains { $0.portType == .builtInSpeaker }
        if hasBuiltIn { return true }
        // Watch Ultra always has a speaker even if not currently routed
        // Check model name heuristic
        let model = WKInterfaceDevice.current().model.lowercased()
        return model.contains("ultra")
    }
    
    // MARK: - Audio Session Configuration
    
    private func configureAudioSession() {
        let session = AVAudioSession.sharedInstance()
        do {
            if useSpeakerMode {
                // Speaker mode: .default policy allows speaker output
                try session.setCategory(.playback, mode: .default, policy: .default)
                print("[WatchAudio] Session: .playback / .default (speaker mode)")
            } else {
                // Bluetooth mode: .longFormAudio requires BT/AirPlay
                try session.setCategory(.playback, mode: .default, policy: .longFormAudio)
                print("[WatchAudio] Session: .playback / .longFormAudio (bluetooth mode)")
            }
            updateRouteInfo()
        } catch {
            print("[WatchAudio] Session config FAILED: \(error.localizedDescription)")
        }
    }
    
    private func reconfigureAudioSession() {
        let wasPlaying = isPlaying
        if wasPlaying { player?.pause() }
        configureAudioSession()
        if useSpeakerMode {
            startWorkoutSession()
        } else {
            stopWorkoutSession()
        }
        if wasPlaying { player?.play() }
        updateRouteInfo()
    }
    
    // MARK: - HKWorkoutSession (keeps app alive for speaker mode)
    
    private func startWorkoutSession() {
        guard workoutSession == nil else { return }
        guard HKHealthStore.isHealthDataAvailable() else {
            print("[WatchAudio] HealthKit not available")
            return
        }
        
        let config = HKWorkoutConfiguration()
        config.activityType = .mindAndBody  // Least intrusive workout type
        config.locationType = .indoor
        
        do {
            let session = try HKWorkoutSession(healthStore: healthStore, configuration: config)
            let builder = session.associatedWorkoutBuilder()
            builder.dataSource = HKLiveWorkoutDataSource(healthStore: healthStore, workoutConfiguration: config)
            
            session.delegate = self
            builder.delegate = self
            
            session.startActivity(with: Date())
            builder.beginCollection(withStart: Date()) { success, error in
                if let error = error {
                    print("[WatchAudio] Workout builder start failed: \(error.localizedDescription)")
                } else {
                    print("[WatchAudio] Workout session started (speaker background mode)")
                }
            }
            
            workoutSession = session
            workoutBuilder = builder
        } catch {
            print("[WatchAudio] Failed to start workout session: \(error.localizedDescription)")
        }
    }
    
    private func stopWorkoutSession() {
        guard let session = workoutSession else { return }
        session.end()
        workoutBuilder?.endCollection(withEnd: Date()) { [weak self] success, error in
            self?.workoutBuilder?.finishWorkout { workout, error in
                print("[WatchAudio] Workout session ended")
            }
        }
        workoutSession = nil
        workoutBuilder = nil
    }
    
    // MARK: - Session Activation (Bluetooth mode only)
    
    func activateSession() async -> Bool {
        if useSpeakerMode {
            // Speaker mode doesn't need activation — just start workout
            await MainActor.run {
                startWorkoutSession()
                isSessionActive = true
                updateRouteInfo()
            }
            return true
        }
        
        let session = AVAudioSession.sharedInstance()
        
        let result = await withCheckedContinuation { (continuation: CheckedContinuation<(Bool, String?), Never>) in
            session.activate(options: []) { success, error in
                continuation.resume(returning: (success, error?.localizedDescription))
            }
        }
        
        await MainActor.run {
            if result.0 {
                self.isSessionActive = true
                self.activationError = nil
                self.updateRouteInfo()
                print("[WatchAudio] Session activated OK. Route: \(self.currentRouteName)")
            } else {
                self.isSessionActive = false
                self.activationError = result.1 ?? "Unknown error"
                print("[WatchAudio] Session activation FAILED: \(result.1 ?? "?")")
            }
        }
        
        return result.0
    }
    
    // MARK: - Route Monitoring
    
    private func observeRouteChanges() {
        NotificationCenter.default.addObserver(
            self, selector: #selector(handleRouteChange),
            name: AVAudioSession.routeChangeNotification, object: nil
        )
        NotificationCenter.default.addObserver(
            self, selector: #selector(handleInterruption),
            name: AVAudioSession.interruptionNotification, object: nil
        )
    }
    
    @objc private func handleRouteChange(_ notification: Notification) {
        guard let info = notification.userInfo,
              let reasonValue = info[AVAudioSessionRouteChangeReasonKey] as? UInt,
              let reason = AVAudioSession.RouteChangeReason(rawValue: reasonValue) else { return }
        
        DispatchQueue.main.async {
            self.updateRouteInfo()
            switch reason {
            case .oldDeviceUnavailable:
                if !self.useSpeakerMode {
                    print("[WatchAudio] Bluetooth disconnected — pausing")
                    self.pause()
                }
            case .newDeviceAvailable:
                print("[WatchAudio] New route: \(self.currentRouteName)")
            default:
                print("[WatchAudio] Route changed: \(self.currentRouteName)")
            }
        }
    }
    
    @objc private func handleInterruption(_ notification: Notification) {
        guard let info = notification.userInfo,
              let typeValue = info[AVAudioSessionInterruptionTypeKey] as? UInt,
              let type = AVAudioSession.InterruptionType(rawValue: typeValue) else { return }
        
        DispatchQueue.main.async {
            switch type {
            case .began:
                self.pause()
            case .ended:
                if let opts = info[AVAudioSessionInterruptionOptionKey] as? UInt {
                    if AVAudioSession.InterruptionOptions(rawValue: opts).contains(.shouldResume) {
                        self.resume()
                    }
                }
            @unknown default: break
            }
        }
    }
    
    private func updateRouteInfo() {
        let route = AVAudioSession.sharedInstance().currentRoute
        if let output = route.outputs.first {
            currentRouteName = output.portName
            isBluetoothConnected = [.bluetoothA2DP, .bluetoothLE, .bluetoothHFP, .airPlay].contains(output.portType)
        } else {
            currentRouteName = useSpeakerMode ? "Speaker" : "No Output"
            isBluetoothConnected = false
        }
    }
    
    // MARK: - Playback
    
    func play(song: Song, fromQueue: [Song]? = nil, at index: Int = 0) {
        if let q = fromQueue {
            queue = shuffleEnabled ? q.shuffled() : q
            queueIndex = index
        }
        currentSong = song
        
        let url: URL?
        if let localURL = WatchOfflineStore.shared.localURL(for: song.id) {
            url = localURL
        } else {
            url = WatchSessionManager.shared.streamURL(songId: song.id, maxBitRate: 192)
        }
        guard let playURL = url else {
            print("[WatchAudio] No URL for: \(song.title)")
            return
        }
        
        if useSpeakerMode {
            // Speaker mode: start workout if needed, then play
            startWorkoutSession()
            isSessionActive = true
            playFromURL(playURL)
            return
        }
        
        // Bluetooth mode: activate session if needed
        if isSessionActive && isBluetoothConnected {
            playFromURL(playURL)
            return
        }
        
        pendingPlayURL = playURL
        pendingSong = song
        Task {
            _ = await activateSession()
            await MainActor.run {
                if let url = self.pendingPlayURL {
                    self.playFromURL(url)
                }
                self.pendingPlayURL = nil
                self.pendingSong = nil
            }
        }
    }
    
    private func playFromURL(_ url: URL) {
        levelTimer?.invalidate()
        if let observer = timeObserver { player?.removeTimeObserver(observer); timeObserver = nil }
        
        let asset = AVURLAsset(url: url)
        playerItem = AVPlayerItem(asset: asset)
        
        if player == nil { player = AVPlayer(playerItem: playerItem) }
        else { player?.replaceCurrentItem(with: playerItem) }
        
        player?.volume = volume
        player?.play()
        isPlaying = true
        
        let interval = CMTime(seconds: 1.0, preferredTimescale: 1)
        timeObserver = player?.addPeriodicTimeObserver(forInterval: interval, queue: .main) { [weak self] time in
            guard let self = self else { return }
            self.currentTime = time.seconds
            if let dur = self.playerItem?.duration.seconds, !dur.isNaN { self.duration = dur }
            self.updateNowPlayingInfo()
        }
        
        levelTimer = Timer.scheduledTimer(withTimeInterval: 1.0/30.0, repeats: true) { [weak self] _ in
            guard let self = self, self.isPlaying else {
                self?.audioLevels = Array(repeating: 0, count: 8)
                return
            }
            self.audioLevels = (0..<8).map { i in
                let target = Float.random(in: 0.1...0.85)
                let current = self.audioLevels.count > i ? self.audioLevels[i] : 0.1
                return current + (target - current) * 0.2
            }
        }
        
        NotificationCenter.default.removeObserver(self, name: .AVPlayerItemDidPlayToEndTime, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(playerDidFinish), name: .AVPlayerItemDidPlayToEndTime, object: playerItem)
        
        updateNowPlayingInfo()
        print("[WatchAudio] Playing: \(currentSong?.title ?? "?") via \(currentRouteName) (\(useSpeakerMode ? "speaker" : "bluetooth"))")
    }
    
    // MARK: - Transport
    
    func togglePlayPause() { if isPlaying { pause() } else { resume() } }
    
    func pause() {
        player?.pause()
        isPlaying = false
        updateNowPlayingInfo()
    }
    
    func resume() {
        if useSpeakerMode { startWorkoutSession() }
        player?.play()
        isPlaying = true
        updateNowPlayingInfo()
    }
    
    func next() {
        guard !queue.isEmpty else { return }
        if queueIndex < queue.count - 1 { queueIndex += 1 }
        else if repeatMode == .all { queueIndex = 0 }
        else { pause(); return }
        play(song: queue[queueIndex])
    }
    
    func previous() {
        if currentTime > 3 { seek(to: 0); return }
        guard !queue.isEmpty else { return }
        if queueIndex > 0 { queueIndex -= 1 }
        else if repeatMode == .all { queueIndex = queue.count - 1 }
        play(song: queue[queueIndex])
    }
    
    func seek(to time: TimeInterval) {
        player?.seek(to: CMTime(seconds: time, preferredTimescale: 600)) { [weak self] _ in
            self?.updateNowPlayingInfo()
        }
        currentTime = time
    }
    
    func setVolume(_ vol: Float) { volume = vol; player?.volume = vol }
    func toggleShuffle() { shuffleEnabled.toggle() }
    func cycleRepeat() {
        switch repeatMode { case .off: repeatMode = .all; case .all: repeatMode = .one; case .one: repeatMode = .off }
    }
    
    @objc private func playerDidFinish() {
        if repeatMode == .one { seek(to: 0); player?.play() } else { next() }
    }
    
    func stop() {
        player?.pause()
        isPlaying = false
        currentSong = nil
        levelTimer?.invalidate(); levelTimer = nil
        audioLevels = Array(repeating: 0, count: 8)
        if let observer = timeObserver { player?.removeTimeObserver(observer); timeObserver = nil }
        if useSpeakerMode { stopWorkoutSession() }
    }
    
    // MARK: - Now Playing
    
    private func updateNowPlayingInfo() {
        var info: [String: Any] = [:]
        info[MPMediaItemPropertyTitle] = currentSong?.title ?? "Unknown"
        info[MPMediaItemPropertyArtist] = currentSong?.artist ?? "Unknown"
        info[MPMediaItemPropertyAlbumTitle] = currentSong?.album ?? ""
        info[MPNowPlayingInfoPropertyElapsedPlaybackTime] = currentTime
        info[MPMediaItemPropertyPlaybackDuration] = duration
        info[MPNowPlayingInfoPropertyPlaybackRate] = isPlaying ? 1.0 : 0.0
        MPNowPlayingInfoCenter.default().nowPlayingInfo = info
    }
    
    // MARK: - Remote Controls
    
    private func setupRemoteControls() {
        let c = MPRemoteCommandCenter.shared()
        c.playCommand.addTarget { [weak self] _ in self?.resume(); return .success }
        c.pauseCommand.addTarget { [weak self] _ in self?.pause(); return .success }
        c.togglePlayPauseCommand.addTarget { [weak self] _ in self?.togglePlayPause(); return .success }
        c.nextTrackCommand.addTarget { [weak self] _ in self?.next(); return .success }
        c.previousTrackCommand.addTarget { [weak self] _ in self?.previous(); return .success }
        c.changePlaybackPositionCommand.addTarget { [weak self] event in
            guard let e = event as? MPChangePlaybackPositionCommandEvent else { return .commandFailed }
            self?.seek(to: e.positionTime); return .success
        }
    }
    
    // MARK: - Helpers
    
    var progressPercent: Double { guard duration > 0 else { return 0 }; return currentTime / duration }
    var currentTimeFormatted: String { formatTime(currentTime) }
    var remainingTimeFormatted: String { "-" + formatTime(max(0, duration - currentTime)) }
    private func formatTime(_ seconds: TimeInterval) -> String {
        let s = Int(max(0, seconds)); return String(format: "%d:%02d", s / 60, s % 60)
    }
}

// MARK: - HKWorkoutSession Delegate

extension WatchAudioPlayer: HKWorkoutSessionDelegate {
    func workoutSession(_ workoutSession: HKWorkoutSession, didChangeTo toState: HKWorkoutSessionState, from fromState: HKWorkoutSessionState, date: Date) {
        print("[WatchAudio] Workout state: \(fromState.rawValue) → \(toState.rawValue)")
        if toState == .ended {
            DispatchQueue.main.async {
                self.workoutSession = nil
                self.workoutBuilder = nil
            }
        }
    }
    
    func workoutSession(_ workoutSession: HKWorkoutSession, didFailWithError error: Error) {
        print("[WatchAudio] Workout session failed: \(error.localizedDescription)")
    }
}

// MARK: - HKLiveWorkoutBuilder Delegate

extension WatchAudioPlayer: HKLiveWorkoutBuilderDelegate {
    func workoutBuilderDidCollectEvent(_ workoutBuilder: HKLiveWorkoutBuilder) {}
    func workoutBuilder(_ workoutBuilder: HKLiveWorkoutBuilder, didCollectDataOf collectedTypes: Set<HKSampleType>) {}
}