import Foundation
import SwiftUI

/// ViewModel wrapping the AudioEngine with additional UI state.
@MainActor
@Observable
final class PlayerViewModel {
    let audioEngine = AudioEngine()
    let streamingPlayer = StreamingPlayer()

    /// True when playing a cloud track via StreamingPlayer (vs local via AudioEngine).
    var isCloudPlayback = false

    /// The cloud track info when streaming (non-SwiftData, transient).
    var currentCloudTrack: ChadTrack?

    /// True when the streaming player is buffering.
    var isBuffering: Bool { streamingPlayer.isBuffering }

    // MARK: - UI State

    var showingWaveform = true
    var waveformSamples: [WaveformGenerator.WaveformSample] = []
    var isLoadingWaveform = false

    /// ID of the currently playing playlist entry (if playing from a playlist).
    var currentPlayingEntryID: UUID?

    /// The playlist currently being played through.
    var currentPlaylist: Playlist?

    /// The currently selected (cursor) entry ID — updated by PlaylistEntryList.
    var cursorEntryID: UUID?

    /// Shuffle mode.
    var shuffleEnabled: Bool = false

    /// Repeat mode.
    enum RepeatMode: String, CaseIterable {
        case off = "Off"
        case all = "Repeat All"
        case one = "Repeat One"
    }
    var repeatMode: RepeatMode = .off

    // MARK: - Synced State (updated from AudioEngine)

    var isPlaying: Bool = false
    var currentTime: TimeInterval = 0
    var duration: TimeInterval = 0
    var currentTrack: Track?

    var volume: Float {
        get { isCloudPlayback ? streamingPlayer.volume : audioEngine.volume }
        set {
            audioEngine.volume = newValue
            streamingPlayer.volume = newValue
        }
    }

    var progress: Double {
        guard duration > 0 else { return 0 }
        return currentTime / duration
    }

    var currentTimeFormatted: String {
        formatTime(currentTime)
    }

    var durationFormatted: String {
        formatTime(duration)
    }

    var remainingTimeFormatted: String {
        "-" + formatTime(duration - currentTime)
    }

    @ObservationIgnored private var syncTimer: Timer?
    @ObservationIgnored private var stateSaveCounter = 0
    @ObservationIgnored private var nowPlayingCounter = 0

    init() {
        startSyncTimer()
        audioEngine.onPlaybackFinished = { [weak self] in
            self?.playNext()
        }
        streamingPlayer.onPlaybackFinished = { [weak self] in
            self?.playNext()
        }
        streamingPlayer.onPlaybackError = { [weak self] msg in
            print("PlayerViewModel: Stream error: \(msg)")
            self?.stop()
        }
    }

    /// Periodically sync state from AudioEngine to trigger SwiftUI updates.
    private func startSyncTimer() {
        syncTimer = Timer.scheduledTimer(withTimeInterval: 1.0 / 30.0, repeats: true) { [weak self] _ in
            Task { @MainActor in
                self?.syncFromEngine()
            }
        }
    }

    private func syncFromEngine() {
        if isCloudPlayback {
            // Sync from StreamingPlayer
            let sp = streamingPlayer
            if isPlaying != sp.isPlaying { isPlaying = sp.isPlaying }
            if abs(currentTime - sp.currentTime) > 0.01 { currentTime = sp.currentTime }
            if duration != sp.duration { duration = sp.duration }
        } else {
            // Sync from AudioEngine
            let engine = audioEngine
            engine.updateCurrentTime()
            if isPlaying != engine.isPlaying { isPlaying = engine.isPlaying }
            if abs(currentTime - engine.currentTime) > 0.01 { currentTime = engine.currentTime }
            if duration != engine.duration { duration = engine.duration }
            if currentTrack !== engine.currentTrack { currentTrack = engine.currentTrack }
        }

        // Save state every ~2 seconds (every 60 sync ticks at 30fps)
        stateSaveCounter += 1
        if stateSaveCounter >= 60 {
            stateSaveCounter = 0
            savePlaybackState()
        }

        // Update Now Playing info every ~1 second
        nowPlayingCounter += 1
        if nowPlayingCounter >= 30 {
            nowPlayingCounter = 0
            updateNowPlaying()
        }
    }

    /// Persist current playback state to UserDefaults.
    private func savePlaybackState() {
        AppState.savePlaybackState(
            playlistID: currentPlaylist?.id,
            entryID: currentPlayingEntryID,
            trackFilePath: currentTrack?.filePath,
            playbackTime: currentTime
        )
    }

    /// Update macOS Now Playing info center (media keys, control center widget).
    private func updateNowPlaying() {
        MediaKeyHandler.shared.updateNowPlaying(
            track: currentTrack,
            isPlaying: isPlaying,
            currentTime: currentTime,
            duration: duration
        )
    }

    // MARK: - Track Loading & Playback

    func loadAndPlay(_ track: Track, entryID: UUID? = nil, playlist: Playlist? = nil) {
        // Cloud track — route to StreamingPlayer
        if track.isCloud, let streamPath = track.cloudStreamPath {
            let client = ChadMusicAPIClient.shared
            guard let url = client.streamURL(for: streamPath) else {
                print("PlayerViewModel: Failed to build stream URL for cloud track")
                return
            }
            // Stop local playback
            audioEngine.stop()
            waveformSamples = []

            isCloudPlayback = true
            currentCloudTrack = nil // no ChadTrack object — using Track directly
            currentTrack = track
            currentPlayingEntryID = entryID
            if let playlist { currentPlaylist = playlist }
            streamingPlayer.loadAndPlay(
                track: ChadTrack(
                    id: track.cloudTrackId ?? "",
                    title: track.title ?? "—",
                    artist: track.artist,
                    albumArtist: nil,
                    album: track.album,
                    duration: track.duration,
                    no: nil,
                    url: streamPath,
                    bitRate: nil,
                    year: track.year,
                    cover: nil
                ),
                streamURL: url,
                authHeaders: client.authHeaders
            )
            syncFromEngine()
            return
        }

        // Local track — use AudioEngine
        if isCloudPlayback {
            streamingPlayer.stop()
            isCloudPlayback = false
            currentCloudTrack = nil
        }
        do {
            try audioEngine.loadTrack(track)
            audioEngine.play()
            currentPlayingEntryID = entryID
            if let playlist { currentPlaylist = playlist }
            syncFromEngine()
            savePlaybackState()
            loadWaveform(for: track)
        } catch {
            print("PlayerViewModel: Failed to load track: \(error)")
        }
    }

    /// Play a cloud track via StreamingPlayer.
    func loadAndPlayCloud(_ track: ChadTrack, streamURL: URL, authHeaders: [String: String]) {
        // Stop local playback first
        audioEngine.stop()
        currentTrack = nil
        currentPlayingEntryID = nil
        currentPlaylist = nil
        waveformSamples = []

        isCloudPlayback = true
        currentCloudTrack = track
        streamingPlayer.loadAndPlay(track: track, streamURL: streamURL, authHeaders: authHeaders)
        syncFromEngine()
    }

    /// Display title — works for both local and cloud tracks.
    var displayTitle: String {
        if isCloudPlayback, let ct = currentCloudTrack {
            return ct.title
        }
        return currentTrack?.title ?? "—"
    }

    /// Display artist — works for both local and cloud tracks.
    var displayArtist: String {
        if isCloudPlayback, let ct = currentCloudTrack {
            return ct.artist ?? ""
        }
        return currentTrack?.artist ?? ""
    }

    func togglePlayPause() {
        if isCloudPlayback {
            streamingPlayer.togglePlayPause()
        } else {
            audioEngine.togglePlayPause()
        }
        syncFromEngine()
    }

    func stop() {
        if isCloudPlayback {
            streamingPlayer.stop()
            isCloudPlayback = false
            currentCloudTrack = nil
        } else {
            audioEngine.stop()
        }
        waveformSamples = []
        currentPlayingEntryID = nil
        syncFromEngine()
    }

    // MARK: - Playlist Navigation

    /// Advance to the next track in the current playlist.
    func playNext() {
        guard let playlist = currentPlaylist,
              let currentID = currentPlayingEntryID else { return }

        let entries = playlist.sortedEntries

        // "Playback follows cursor": play the cursor track if it's different from current
        if PlaylistViewConfig.shared.playbackFollowsCursor,
           let cursorID = cursorEntryID,
           cursorID != currentID,
           let cursorEntry = entries.first(where: { $0.id == cursorID }),
           let track = cursorEntry.track {
            loadAndPlay(track, entryID: cursorEntry.id, playlist: playlist)
            // Don't move cursor — user put it there intentionally
            return
        }

        guard let currentIndex = entries.firstIndex(where: { $0.id == currentID }) else { return }

        // Repeat One: replay same track
        if repeatMode == .one, let track = entries[currentIndex].track {
            loadAndPlay(track, entryID: entries[currentIndex].id)
            cursorEntryID = entries[currentIndex].id
            return
        }

        // Shuffle: pick a random different track
        if shuffleEnabled && entries.count > 1 {
            var randomIndex = currentIndex
            while randomIndex == currentIndex {
                randomIndex = Int.random(in: 0..<entries.count)
            }
            if let track = entries[randomIndex].track {
                loadAndPlay(track, entryID: entries[randomIndex].id)
                cursorEntryID = entries[randomIndex].id
            }
            return
        }

        // Normal sequential
        let nextIndex = currentIndex + 1
        if nextIndex < entries.count, let nextTrack = entries[nextIndex].track {
            loadAndPlay(nextTrack, entryID: entries[nextIndex].id)
            cursorEntryID = entries[nextIndex].id
        } else if repeatMode == .all, let firstTrack = entries.first?.track {
            // Wrap around
            loadAndPlay(firstTrack, entryID: entries[0].id)
            cursorEntryID = entries[0].id
        } else {
            // End of playlist
            stop()
        }
    }

    /// Go back to the previous track in the current playlist.
    func playPrevious() {
        guard let playlist = currentPlaylist,
              let currentID = currentPlayingEntryID else { return }

        let entries = playlist.sortedEntries

        // "Playback follows cursor": play the cursor track if it's different from current
        if PlaylistViewConfig.shared.playbackFollowsCursor,
           let cursorID = cursorEntryID,
           cursorID != currentID,
           let cursorEntry = entries.first(where: { $0.id == cursorID }),
           let track = cursorEntry.track {
            loadAndPlay(track, entryID: cursorEntry.id, playlist: playlist)
            return
        }

        guard let currentIndex = entries.firstIndex(where: { $0.id == currentID }) else { return }

        // If more than 3 seconds in, restart current track; otherwise go to previous
        if currentTime > 3, let track = currentTrack {
            seek(to: 0)
            return
        }

        let prevIndex = currentIndex - 1
        guard prevIndex >= 0,
              let prevTrack = entries[prevIndex].track else { return }

        loadAndPlay(prevTrack, entryID: entries[prevIndex].id)
    }

    func seek(to time: TimeInterval) {
        if isCloudPlayback {
            streamingPlayer.seek(to: time)
        } else {
            audioEngine.seek(to: time)
        }
    }

    func seekToProgress(_ progress: Double) {
        let time = progress * duration
        seek(to: time)
    }

    func skipForward(_ seconds: TimeInterval = 10) {
        if isCloudPlayback {
            streamingPlayer.seek(by: seconds)
        } else {
            audioEngine.seek(by: seconds)
        }
    }

    func skipBackward(_ seconds: TimeInterval = 10) {
        if isCloudPlayback {
            streamingPlayer.seek(by: -seconds)
        } else {
            audioEngine.seek(by: -seconds)
        }
    }

    // MARK: - EQ

    func setLowEQ(_ gain: Float) {
        audioEngine.setEQ(band: 0, gain: gain)
    }

    func setMidEQ(_ gain: Float) {
        audioEngine.setEQ(band: 1, gain: gain)
    }

    func setHighEQ(_ gain: Float) {
        audioEngine.setEQ(band: 2, gain: gain)
    }

    // MARK: - Waveform

    func loadWaveform(for track: Track) {
        // Check cache first
        if let cached = track.waveformData,
           let decoded = WaveformGenerator.decodeCachedWaveform(from: cached) {
            waveformSamples = decoded
            return
        }

        isLoadingWaveform = true
        Task {
            do {
                let samples = try await WaveformGenerator.generateWaveform(for: track)
                waveformSamples = samples
            } catch {
                print("PlayerViewModel: Waveform generation failed: \(error)")
                waveformSamples = []
            }
            isLoadingWaveform = false
        }
    }

    // MARK: - Helpers

    private func formatTime(_ time: TimeInterval) -> String {
        let total = max(0, Int(time))
        let minutes = total / 60
        let seconds = total % 60
        return String(format: "%d:%02d", minutes, seconds)
    }
}