import Foundation
import SwiftData
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 {
        didSet {
            if shuffleEnabled {
                upNext.shuffle()
            } else {
                rebuildUpNextFromSource()
            }
        }
    }

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

    // MARK: - Queue

    var nowPlayingEntry: QueueEntry?
    var userQueue: [QueueEntry] = []
    var upNext: [QueueEntry] = []
    var history: [QueueEntry] = []

    /// ModelContext for resolving SwiftData track IDs — set from the view layer.
    @ObservationIgnored var modelContext: ModelContext?

    // MARK: - Playback Mode

    /// "playlist" = foobar-style (advance through playlist), "queue" = Spotify-style (queue system).
    @ObservationIgnored
    var playbackMode: String {
        get { UserDefaults.standard.string(forKey: "playbackMode") ?? "queue" }
        set { UserDefaults.standard.set(newValue, forKey: "playbackMode") }
    }

    // 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() {
        restoreQueue()
        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) {
        // Set up queue entry for now playing
        let queueEntry = QueueEntry.from(track: track)
        nowPlayingEntry = queueEntry

        // When starting from a playlist, reset queue state
        if playlist != nil {
            history = []
        }

        // Check for playable local file first (covers both local library tracks and downloaded cloud tracks)
        if track.hasPlayableLocalFile {
            if isCloudPlayback {
                streamingPlayer.stop()
                isCloudPlayback = false
                currentCloudTrack = nil
            }
            do {
                try audioEngine.loadTrack(track, fileURL: track.playableFileURL)
                audioEngine.play()
                currentPlayingEntryID = entryID
                if let playlist {
                    currentPlaylist = playlist
                    rebuildUpNextFromPlaylist(playlist, afterEntryID: entryID)
                }
                syncFromEngine()
                savePlaybackState()
                loadWaveform(for: track)
                persistQueue()
            } catch {
                // Format fallback: if AudioEngine can't open the file (e.g., OGG), try StreamingPlayer
                if track.isCloud, let cachePath = track.localCachePath {
                    print("PlayerViewModel: AudioEngine failed for downloaded file, falling back to StreamingPlayer: \(error)")
                    playViaStreamingPlayer(track: track, url: URL(fileURLWithPath: cachePath), entryID: entryID, playlist: playlist)
                } else {
                    print("PlayerViewModel: Failed to load track: \(error)")
                }
            }
            return
        }

        // Cloud track without local file — 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
            }
            playViaStreamingPlayer(track: track, url: url, entryID: entryID, playlist: playlist)
            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
                rebuildUpNextFromPlaylist(playlist, afterEntryID: entryID)
            }
            syncFromEngine()
            savePlaybackState()
            loadWaveform(for: track)
            persistQueue()
        } catch {
            print("PlayerViewModel: Failed to load track: \(error)")
        }
    }

    /// Route playback through StreamingPlayer (for cloud streaming or format fallback).
    private func playViaStreamingPlayer(track: Track, url: URL, entryID: UUID?, playlist: Playlist?) {
        audioEngine.stop()
        waveformSamples = []

        isCloudPlayback = true
        currentCloudTrack = nil
        currentTrack = track
        currentPlayingEntryID = entryID
        if let playlist {
            currentPlaylist = playlist
            rebuildUpNextFromPlaylist(playlist, afterEntryID: entryID)
        }
        streamingPlayer.loadAndPlay(
            track: ChadTrack(
                id: track.cloudTrackId ?? "",
                title: track.title ?? "—",
                artist: track.artist,
                albumArtist: nil,
                album: track.album,
                duration: track.duration,
                no: nil,
                url: track.cloudStreamPath ?? url.absoluteString,
                bitRate: nil,
                year: track.year,
                cover: nil
            ),
            streamURL: url,
            authHeaders: ChadMusicAPIClient.shared.authHeaders
        )
        syncFromEngine()
        persistQueue()
    }

    /// 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 (Queue-based)

    /// Advance to the next track using the 3-part queue: userQueue → upNext → repeat.
    func playNext() {
        if playbackMode == "playlist" {
            playNextInPlaylist()
        } else {
            playNextInQueueMode()
        }
    }

    /// Playlist mode: advance to next entry in the current playlist (foobar-style).
    private func playNextInPlaylist() {
        if repeatMode == .one, let current = nowPlayingEntry {
            playQueueEntry(current)
            return
        }

        guard let playlist = currentPlaylist,
              let currentID = currentPlayingEntryID else {
            stop()
            return
        }
        let entries = playlist.sortedEntries
        guard let currentIndex = entries.firstIndex(where: { $0.id == currentID }) else {
            stop()
            return
        }

        let nextIndex = currentIndex + 1
        if nextIndex < entries.count, let track = entries[nextIndex].track {
            loadAndPlay(track, entryID: entries[nextIndex].id, playlist: playlist)
        } else if repeatMode == .all, let firstTrack = entries.first?.track {
            loadAndPlay(firstTrack, entryID: entries.first!.id, playlist: playlist)
        } else {
            stop()
        }
    }

    /// Queue mode: advance using userQueue → upNext → repeat (Spotify-style).
    private func playNextInQueueMode() {
        // Repeat One: replay current
        if repeatMode == .one, let current = nowPlayingEntry {
            playQueueEntry(current)
            return
        }

        // Push current to history
        if let current = nowPlayingEntry {
            history.insert(current, at: 0)
            if history.count > 50 { history = Array(history.prefix(50)) }
        }

        // Pop from userQueue first, then upNext
        if !userQueue.isEmpty {
            let next = userQueue.removeFirst()
            nowPlayingEntry = next
            playQueueEntry(next)
            persistQueue()
            return
        }

        if !upNext.isEmpty {
            let next = upNext.removeFirst()
            nowPlayingEntry = next
            playQueueEntry(next)
            persistQueue()
            return
        }

        // Both empty — check repeat all
        if repeatMode == .all, let playlist = currentPlaylist {
            rebuildUpNextFromPlaylist(playlist, afterEntryID: nil)
            if !upNext.isEmpty {
                let next = upNext.removeFirst()
                nowPlayingEntry = next
                playQueueEntry(next)
                persistQueue()
                return
            }
        }

        // Nothing left
        nowPlayingEntry = nil
        stop()
        persistQueue()
    }

    /// Go back to the previous track.
    func playPrevious() {
        if currentTime > 3 {
            seek(to: 0)
            return
        }

        // Try history first
        if !history.isEmpty {
            let prev = history.removeFirst()

            // Push current nowPlaying to front of upNext
            if let current = nowPlayingEntry {
                upNext.insert(current, at: 0)
            }

            nowPlayingEntry = prev
            playQueueEntry(prev)
            persistQueue()
            return
        }

        // Fallback: navigate by playlist position
        guard let playlist = currentPlaylist,
              let currentID = currentPlayingEntryID else { return }
        let entries = playlist.sortedEntries
        guard let currentIndex = entries.firstIndex(where: { $0.id == currentID }),
              currentIndex > 0,
              let prevTrack = entries[currentIndex - 1].track else { return }

        loadAndPlay(prevTrack, entryID: entries[currentIndex - 1].id, playlist: playlist)
    }

    // MARK: - Queue Actions

    /// Add entry to end of user queue.
    func addToQueue(_ entry: QueueEntry) {
        userQueue.append(entry)
        persistQueue()
        // Auto-play if nothing is currently playing
        if !isPlaying && nowPlayingEntry == nil {
            playNext()
        }
    }

    /// Insert entry at front of user queue ("Play Next").
    func playNextInQueue(_ entry: QueueEntry) {
        userQueue.insert(entry, at: 0)
        persistQueue()
    }

    /// Play a track from playlist context — sets as nowPlaying, fills upNext with remainder.
    func playFromPlaylist(track: Track, entryID: UUID, playlist: Playlist) {
        let entry = QueueEntry.from(track: track)
        nowPlayingEntry = entry
        userQueue = []
        history = []

        rebuildUpNextFromPlaylist(playlist, afterEntryID: entryID)

        currentPlaylist = playlist
        currentPlayingEntryID = entryID
        playQueueEntry(entry)
        persistQueue()
    }

    /// Play a cloud track directly — sets as nowPlaying, clears upNext.
    func playCloudTrackDirectly(_ track: ChadTrack, streamURL: URL, authHeaders: [String: String]) {
        let entry = QueueEntry.from(cloudTrack: track)
        nowPlayingEntry = entry
        userQueue = []
        upNext = []
        history = []
        currentPlaylist = nil
        currentPlayingEntryID = nil

        loadAndPlayCloud(track, streamURL: streamURL, authHeaders: authHeaders)
        persistQueue()
    }

    func removeFromQueue(entry: QueueEntry) {
        userQueue.removeAll { $0.id == entry.id }
        upNext.removeAll { $0.id == entry.id }
        persistQueue()
    }

    func clearQueue() {
        userQueue.removeAll()
        upNext.removeAll()
        persistQueue()
    }

    func moveUserQueueEntry(from source: IndexSet, to destination: Int) {
        userQueue.move(fromOffsets: source, toOffset: destination)
        persistQueue()
    }

    func moveUpNextEntry(from source: IndexSet, to destination: Int) {
        upNext.move(fromOffsets: source, toOffset: destination)
        persistQueue()
    }

    // MARK: - Queue Entry Playback

    private func playQueueEntry(_ entry: QueueEntry) {
        switch entry.source {
        case .swiftDataTrack(let trackPersistentID, _, _):
            // Try to resolve via modelContext
            if let ctx = modelContext, let trackID = UUID(uuidString: trackPersistentID) {
                let descriptor = FetchDescriptor<Track>(
                    predicate: #Predicate<Track> { $0.id == trackID }
                )
                if let track = (try? ctx.fetch(descriptor))?.first {
                    loadAndPlayDirect(track)
                    return
                }
            }
            // Fallback: resolve from the current playlist entries
            if let playlist = currentPlaylist,
               let trackID = UUID(uuidString: trackPersistentID),
               let playlistEntry = playlist.sortedEntries.first(where: { $0.track?.id == trackID }),
               let track = playlistEntry.track {
                currentPlayingEntryID = playlistEntry.id
                loadAndPlayDirect(track)
                return
            }
            print("PlayerViewModel: playQueueEntry — track not found: \(trackPersistentID)")
            skipBrokenEntry()

        case .cloudDirect(_, let streamPath):
            let client = ChadMusicAPIClient.shared
            guard let url = client.streamURL(for: streamPath) else {
                print("PlayerViewModel: playQueueEntry — failed to build stream URL: \(streamPath)")
                skipBrokenEntry()
                return
            }
            let chadTrack = ChadTrack(
                id: entry.id.uuidString,
                title: entry.title,
                artist: entry.artist,
                albumArtist: nil,
                album: nil,
                duration: entry.duration,
                no: nil,
                url: streamPath,
                bitRate: nil,
                year: nil,
                cover: nil
            )
            loadAndPlayCloud(chadTrack, streamURL: url, authHeaders: client.authHeaders)
        }
    }

    /// Internal: play a track without modifying queue state (used by playQueueEntry).
    private func loadAndPlayDirect(_ track: Track) {
        // Check for playable local file first (local library or downloaded cloud track)
        if track.hasPlayableLocalFile {
            if isCloudPlayback {
                streamingPlayer.stop()
                isCloudPlayback = false
                currentCloudTrack = nil
            }
            do {
                try audioEngine.loadTrack(track, fileURL: track.playableFileURL)
                audioEngine.play()
                syncFromEngine()
                savePlaybackState()
                loadWaveform(for: track)
            } catch {
                // Format fallback for downloaded cloud tracks
                if track.isCloud, let cachePath = track.localCachePath {
                    print("PlayerViewModel: AudioEngine failed for downloaded file, falling back to StreamingPlayer: \(error)")
                    playViaStreamingPlayer(track: track, url: URL(fileURLWithPath: cachePath), entryID: nil, playlist: nil)
                } else {
                    print("PlayerViewModel: Failed to load track: \(error)")
                }
            }
            return
        }

        // Cloud track without local file — stream
        if track.isCloud, let streamPath = track.cloudStreamPath {
            let client = ChadMusicAPIClient.shared
            guard let url = client.streamURL(for: streamPath) else { return }
            audioEngine.stop()
            waveformSamples = []
            isCloudPlayback = true
            currentCloudTrack = nil
            currentTrack = track
            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 library track
        if isCloudPlayback {
            streamingPlayer.stop()
            isCloudPlayback = false
            currentCloudTrack = nil
        }
        do {
            try audioEngine.loadTrack(track)
            audioEngine.play()
            syncFromEngine()
            savePlaybackState()
            loadWaveform(for: track)
        } catch {
            print("PlayerViewModel: Failed to load track: \(error)")
        }
    }

    @ObservationIgnored private var skipCount = 0
    private static let maxSkips = 20

    private func skipBrokenEntry() {
        skipCount += 1
        guard skipCount <= Self.maxSkips else {
            print("PlayerViewModel: exceeded \(Self.maxSkips) skips, stopping")
            skipCount = 0
            userQueue.removeAll()
            upNext.removeAll()
            stop()
            return
        }
        playNext()
    }

    // MARK: - Queue Helpers

    private func rebuildUpNextFromPlaylist(_ playlist: Playlist, afterEntryID: UUID?) {
        let entries = playlist.sortedEntries
        var startIndex = 0
        if let afterID = afterEntryID,
           let idx = entries.firstIndex(where: { $0.id == afterID }) {
            startIndex = idx + 1
        }

        upNext = entries[startIndex...].compactMap { entry -> QueueEntry? in
            guard let track = entry.track else { return nil }
            return QueueEntry.from(track: track)
        }

        if shuffleEnabled {
            upNext.shuffle()
        }
    }

    private func rebuildUpNextFromSource() {
        guard let playlist = currentPlaylist else { return }
        rebuildUpNextFromPlaylist(playlist, afterEntryID: currentPlayingEntryID)
    }

    // MARK: - Queue Persistence

    private static let queueKey = "mixboard.queueState"

    private struct PersistedQueue: Codable {
        let nowPlaying: QueueEntry?
        let userQueue: [QueueEntry]
        let upNext: [QueueEntry]
    }

    private func persistQueue() {
        let state = PersistedQueue(nowPlaying: nowPlayingEntry, userQueue: userQueue, upNext: upNext)
        if let data = try? JSONEncoder().encode(state) {
            UserDefaults.standard.set(data, forKey: Self.queueKey)
        }
    }

    private func restoreQueue() {
        guard let data = UserDefaults.standard.data(forKey: Self.queueKey),
              let state = try? JSONDecoder().decode(PersistedQueue.self, from: data) else { return }
        nowPlayingEntry = state.nowPlaying
        userQueue = state.userQueue
        upNext = state.upNext
    }

    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)
    }
}