import SwiftUI
import MusicKit

struct AppleMusicTrack: Identifiable, Equatable {
    let id: String
    let title: String
    let artist: String
    let album: String
    let duration: Double
    let artwork: URL?
}
struct AppleMusicPlaylist: Identifiable, Equatable { let id: String;let name: String }
struct AppleMusicPage { let tracks: [AppleMusicTrack];let hasMore: Bool }
enum AppleMusicAccess { case notDetermined,authorized,denied,restricted }
struct AppleMusicQueueItem: Identifiable, Equatable { let id: String;let title: String;let artist: String;let current: Bool }
struct AppleMusicPlayback: Equatable { var title = "";var artist = "";var playing = false;var position: Double = 0;var duration: Double = 0;var queue = [AppleMusicQueueItem]() }

@MainActor protocol AppleMusicClient: AnyObject {
    var access: AppleMusicAccess { get }
    func authorize() async -> AppleMusicAccess
    func subscribed() async throws -> Bool
    func playlists() async throws -> [AppleMusicPlaylist]
    func browse(query: String,playlist: String?,offset: Int) async throws -> AppleMusicPage
    func play(_ id: String) async throws
    func enqueue(_ id: String) async throws
    func resume() async throws
    func pause()
    func stop()
    func seek(_ seconds: Double)
    func next() async throws
    var playback: AppleMusicPlayback { get }
}

/// Public MusicKit playback stays inside Apple's player; protected streams are
/// never passed to AVAudioFile, waveform analysis or the local deck DSP graph.
@available(macOS 14.0, *) @MainActor final class NativeAppleMusicClient: AppleMusicClient {
    private var tracks = [String:MusicKit.Song]()
    private var playlistItems = [String:MusicKit.Playlist]()
    private var musicPlayer: ApplicationMusicPlayer { .shared }
    var access: AppleMusicAccess {
        switch MusicAuthorization.currentStatus {
        case .authorized:return .authorized
        case .denied:return .denied
        case .restricted:return .restricted
        default:return .notDetermined
        }
    }
    func authorize() async -> AppleMusicAccess { _ = await MusicAuthorization.request();return access }
    func subscribed() async throws -> Bool { try await MusicSubscription.current.canPlayCatalogContent }
    private func remember(_ songs: [MusicKit.Song]) -> [AppleMusicTrack] {
        songs.map { song in
            tracks[song.id.rawValue] = song
            return AppleMusicTrack(id:song.id.rawValue,title:song.title,artist:song.artistName,album:song.albumTitle ?? "",duration:song.duration ?? 0,artwork:song.artwork?.url(width:80,height:80))
        }
    }
    func playlists() async throws -> [AppleMusicPlaylist] {
        var request = MusicLibraryRequest<MusicKit.Playlist>();request.limit = 100
        var result = [AppleMusicPlaylist]()
        while true {
            try Task.checkCancellation()
            let response = try await request.response()
            for item in response.items { playlistItems[item.id.rawValue] = item;result.append(.init(id:item.id.rawValue,name:item.name)) }
            if !response.items.hasNextBatch { break };request.offset += response.items.count
        }
        return result
    }
    func browse(query: String,playlist: String?,offset: Int) async throws -> AppleMusicPage {
        if !query.isEmpty {
            var request = MusicCatalogSearchRequest(term:query,types:[MusicKit.Song.self]);request.limit = 50;request.offset = offset
            let response = try await request.response()
            return .init(tracks:remember(Array(response.songs)),hasMore:response.songs.hasNextBatch)
        }
        if let playlist,let item = playlistItems[playlist] {
            let detailed = try await item.with([.tracks])
            guard var collection = detailed.tracks else { return .init(tracks:[],hasMore:false) }
            var all = Array(collection)
            while all.count < offset+50,collection.hasNextBatch,let next = try await collection.nextBatch(limit:50) {
                try Task.checkCancellation();collection = next;all.append(contentsOf:next)
            }
            let songs = all.dropFirst(offset).prefix(50).compactMap { track -> MusicKit.Song? in
                if case .song(let song) = track { return song };return nil
            }
            return .init(tracks:remember(songs),hasMore:all.count > offset+50 || collection.hasNextBatch)
        }
        var request = MusicLibraryRequest<MusicKit.Song>();request.limit = 50;request.offset = offset
        let response = try await request.response()
        return .init(tracks:remember(Array(response.items)),hasMore:response.items.hasNextBatch)
    }
    private func song(_ id: String) throws -> MusicKit.Song {
        guard let song = tracks[id] else { throw LibraryError.message("Refresh Apple Music and select the track again.") };return song
    }
    func play(_ id: String) async throws { musicPlayer.queue = .init(for:[try song(id)]);try await musicPlayer.play() }
    func enqueue(_ id: String) async throws { try await musicPlayer.queue.insert(song(id),position:.tail) }
    func resume() async throws { try await musicPlayer.play() }
    func pause() { musicPlayer.pause() }
    func stop() { musicPlayer.stop() }
    func seek(_ seconds: Double) { musicPlayer.playbackTime = max(0,seconds) }
    func next() async throws { try await musicPlayer.skipToNextEntry() }
    var playback: AppleMusicPlayback {
        let entry = musicPlayer.queue.currentEntry
        var duration: Double = 0
        if case .song(let song) = entry?.item { duration = song.duration ?? 0 }
        let queue = musicPlayer.queue.entries.map { AppleMusicQueueItem(id:$0.id,title:$0.title,artist:$0.subtitle ?? "",current:$0.id == entry?.id) }
        return .init(title:entry?.title ?? "",artist:entry?.subtitle ?? "",playing:musicPlayer.state.playbackStatus == .playing,position:musicPlayer.playbackTime,duration:duration,queue:queue)
    }
}

@available(macOS 14.0, *) @MainActor final class AppleMusicTransportState: ObservableObject {
    @Published var value = AppleMusicPlayback()
}
@available(macOS 14.0, *) @MainActor final class AppleMusicSession: ObservableObject {
    @Published private(set) var access: AppleMusicAccess
    @Published private(set) var canPlay = false
    @Published private(set) var tracks = [AppleMusicTrack]()
    @Published private(set) var playlists = [AppleMusicPlaylist]()
    @Published private(set) var busy = false
    @Published private(set) var loadingMore = false
    @Published private(set) var hasMore = false
    let transport = AppleMusicTransportState()
    var playback: AppleMusicPlayback {
        get { transport.value }
        set { if newValue != transport.value { transport.value = newValue } }
    }
    @Published var error: String?
    @Published var query = ""
    @Published var playlist: String?
    private let client: AppleMusicClient
    private var browseTask: Task<Void,Never>?
    private var playbackTask: Task<Void,Never>?
    private var generation = UUID()
    init(client: AppleMusicClient? = nil) { let client = client ?? NativeAppleMusicClient();self.client = client;access = client.access }
    deinit { browseTask?.cancel();playbackTask?.cancel() }
    func connect() async {
        guard !busy else { return };browseTask?.cancel();generation = UUID();canPlay = false;tracks = [];busy = true;error = nil
        access = await client.authorize()
        guard access == .authorized else {
            busy = false;error = access == .restricted ? "Apple Music access is restricted on this Mac." : "Allow KJMix Pro in System Settings → Privacy & Security → Media & Apple Music.";return
        }
        do { canPlay = try await client.subscribed();playlists = try await client.playlists() }
        catch { self.error = "Apple Music could not connect. Check your internet connection, Apple Music subscription and this app’s MusicKit App Service configuration. \(error.localizedDescription)" }
        busy = false
        if error == nil { reload() }
    }
    func reload() {
        browseTask?.cancel();generation = UUID();let token = generation
        tracks = [];hasMore = false;loadingMore = false
        guard access == .authorized else { return }
        busy = true;error = nil
        let query = query.trimmingCharacters(in:.whitespacesAndNewlines),playlist = playlist
        browseTask = Task { [weak self] in
            guard let self else { return }
            do {
                let page = try await client.browse(query:query,playlist:playlist,offset:0)
                guard !Task.isCancelled,generation == token else { return }
                tracks = page.tracks;hasMore = page.hasMore;busy = false
            } catch { guard generation == token,!Task.isCancelled else { return };self.error = error.localizedDescription;busy = false }
        }
    }
    func more() {
        guard hasMore,!busy,!loadingMore else { return };loadingMore = true
        let token = generation,offset = tracks.count,query = query.trimmingCharacters(in:.whitespacesAndNewlines),playlist = playlist
        browseTask = Task { [weak self] in
            guard let self else { return }
            do {
                let page = try await client.browse(query:query,playlist:playlist,offset:offset)
                guard !Task.isCancelled,generation == token else { return }
                let existing = Set(tracks.map(\.id));tracks += page.tracks.filter{!existing.contains($0.id)};hasMore = page.hasMore;loadingMore = false
            } catch { guard generation == token,!Task.isCancelled else { return };self.error = error.localizedDescription;loadingMore = false }
        }
    }
    func play(_ track: AppleMusicTrack) async {
        guard canPlay else { error = "An active Apple Music subscription is required for full playback.";return }
        do { try await client.play(track.id);observePlayback() } catch { self.error = error.localizedDescription }
    }
    func enqueue(_ track: AppleMusicTrack) async {
        guard canPlay else { error = "An active Apple Music subscription is required for full playback.";return }
        do { try await client.enqueue(track.id);observePlayback() } catch { self.error = error.localizedDescription }
    }
    func toggle() async {
        do { if playback.playing { client.pause() } else { try await client.resume() };observePlayback() } catch { self.error = error.localizedDescription }
    }
    func pause() { client.pause();playback = client.playback }
    func stop() { client.stop();playback = client.playback;playbackTask?.cancel();playbackTask = nil }
    func seek(_ value: Double) { client.seek(min(playback.duration,max(0,value)));playback = client.playback }
    func next() async { do { try await client.next();observePlayback() } catch { self.error = error.localizedDescription } }
    private func observePlayback() {
        playback = client.playback
        guard playbackTask == nil else { return }
        playbackTask = Task { [weak self] in
            while !Task.isCancelled {
                do { try await Task.sleep(nanoseconds:250_000_000) } catch { return }
                guard let self else { return };self.playback = self.client.playback
            }
        }
    }
}

@available(macOS 14.0, *) struct AppleMusicBrowser: View {
    @ObservedObject var session: AppleMusicSession
    @State private var pendingPlay: AppleMusicTrack?
    @State private var pendingResume = false
    let hasPlayingDeck: () -> Bool
    let stopDecks: () -> Void
    private func requestPlay(_ track: AppleMusicTrack) {
        if hasPlayingDeck() { pendingPlay = track } else { Task { await session.play(track) } }
    }
    var body: some View {
        VStack(spacing:0) {
            HStack(spacing:14) {
                Label("Apple Music",systemImage:"music.note").font(.title3.bold()).foregroundStyle(.pink)
                Picker("Apple Music library",selection:$session.playlist) {
                    Text("My Library").tag(nil as String?)
                    ForEach(session.playlists) { Text($0.name).tag(Optional($0.id)) }
                }.labelsHidden().frame(maxWidth:200).disabled(session.access != .authorized)
                Spacer()
                StudioSearchField(placeholder:"Search Apple Music catalog",text:$session.query).frame(maxWidth:320)
                    .onSubmit { session.reload() }
                Button("Search") { session.reload() }.buttonStyle(LibraryActionButtonStyle(tint:.pink)).disabled(session.access != .authorized)
                Button(session.access == .authorized ? "Refresh Connection" : "Connect Apple Music") { Task { await session.connect() } }
                    .buttonStyle(LibraryActionButtonStyle(tint:.pink,prominent:true)).disabled(session.busy)
            }.padding(14)
            if let error = session.error { HStack { Image(systemName:"exclamationmark.circle.fill").foregroundStyle(.orange);Text(error).font(.callout);Spacer();Button("Dismiss") { session.error = nil } }.padding(12).background(Color.orange.opacity(0.1)) }
            if session.busy { ProgressView("Loading Apple Music…").padding() }
            if session.access != .authorized {
                VStack(spacing:12) {
                    Image(systemName:"music.note.list").font(.system(size:34)).foregroundStyle(.pink)
                    Text("Your Apple Music library and playlists").font(.headline)
                    Text("Connect to browse your library, search the catalog and play through Apple Music.").foregroundStyle(.secondary)
                }.frame(maxWidth:.infinity,maxHeight:.infinity)
            } else {
                Table(session.tracks) {
                    TableColumn("Track") { track in
                        HStack(spacing:10) {
                            AsyncImage(url:track.artwork) { image in image.resizable().scaledToFill() } placeholder: { Image(systemName:"music.note").frame(maxWidth:.infinity,maxHeight:.infinity).background(Color.pink.opacity(0.12)) }.frame(width:32,height:32).clipShape(RoundedRectangle(cornerRadius:5))
                            Text(track.title).lineLimit(1)
                        }.padding(.vertical,3).onTapGesture(count:2) { requestPlay(track) }
                        .contextMenu { Button("Play in Apple Music") { requestPlay(track) };Button("Add to Apple Music Queue") { Task { await session.enqueue(track) } } }
                    }.width(min:180,ideal:300)
                    TableColumn("Artist",value:\.artist).width(min:100,ideal:180)
                    TableColumn("Album",value:\.album).width(min:100,ideal:180)
                    TableColumn("Time") { Text(Self.time(track:$0.duration)).monospacedDigit() }.width(60)
                    TableColumn("Playback") { track in
                        HStack { Button { requestPlay(track) } label: { Image(systemName:"play.fill") };Button { Task { await session.enqueue(track) } } label: { Image(systemName:"text.badge.plus") } }.disabled(!session.canPlay)
                    }.width(90)
                }
                if session.hasMore { Button(session.loadingMore ? "Loading…" : "Load More") { session.more() }.disabled(session.loadingMore).padding(8) }
            }
            Divider()
            AppleMusicTransportBar(session:session,toggle:{
                if hasPlayingDeck(),!session.playback.playing { pendingResume = true }
                else { Task { await session.toggle() } }
            })
            Text("MusicKit playback uses the system audio output. Deck EQ, sync, loops, waveform analysis and recording apply to local tracks.").font(.caption).foregroundStyle(.secondary).padding(.horizontal,14).padding(.bottom,10)
        }.background(Color(red:0.095,green:0.11,blue:0.135)).clipShape(RoundedRectangle(cornerRadius:10))
        .onChange(of:session.playlist) { _ in session.query = "";session.reload() }
        .onChange(of:session.query) { value in if value.isEmpty { session.reload() } }
        .alert("Stop deck playback?",isPresented:Binding(get:{pendingPlay != nil || pendingResume},set:{if !$0 { pendingPlay = nil;pendingResume = false }})) {
            Button("Cancel",role:.cancel) { pendingPlay = nil;pendingResume = false }
            Button("Stop Decks & Play") {
                stopDecks()
                let track = pendingPlay;pendingPlay = nil;pendingResume = false
                Task { if let track { await session.play(track) } else { await session.toggle() } }
            }
        } message: { Text("Apple Music uses its own player. Stop the playing decks before starting Apple Music?") }
    }
    static func time(track: Double) -> String { guard track.isFinite else { return "0:00" };let seconds = max(0,Int(track));return String(format:"%d:%02d",seconds/60,seconds%60) }
}

@available(macOS 14.0, *) private struct AppleMusicTransportBar: View {
    let session: AppleMusicSession
    let toggle: () -> Void
    @State private var queueVisible = false
    @ObservedObject var transport: AppleMusicTransportState
    init(session: AppleMusicSession,toggle: @escaping () -> Void) { self.session = session;self.toggle = toggle;transport = session.transport }
    var body: some View {
        HStack(spacing:14) {
            Button(action:toggle) { Image(systemName:session.playback.playing ? "pause.fill" : "play.fill") }.disabled(session.playback.title.isEmpty)
            Button { session.stop() } label: { Image(systemName:"stop.fill") }.disabled(session.playback.title.isEmpty)
            Button { Task { await session.next() } } label: { Image(systemName:"forward.end.fill") }.disabled(session.playback.title.isEmpty)
            VStack(alignment:.leading,spacing:3) { Text(session.playback.title.isEmpty ? "Choose an Apple Music track" : session.playback.title).fontWeight(.semibold).lineLimit(1);Text(session.playback.artist).font(.caption).foregroundStyle(.secondary).lineLimit(1) }.frame(minWidth:160,maxWidth:300,alignment:.leading)
            Text(AppleMusicBrowser.time(track:session.playback.position)).monospacedDigit()
            Slider(value:Binding(get:{min(session.playback.duration,max(0,session.playback.position))},set:{session.seek($0)}),in:0...max(1,session.playback.duration)).tint(.pink).disabled(session.playback.duration <= 0)
            Text(AppleMusicBrowser.time(track:session.playback.duration)).monospacedDigit()
            Button { queueVisible = true } label: { Label("Queue",systemImage:"text.line.first.and.arrowtriangle.forward") }
        }.buttonStyle(.bordered).padding(14)
        .sheet(isPresented:$queueVisible) {
            VStack(alignment:.leading,spacing:14) {
                HStack { Text("Apple Music Queue").font(.title2.bold());Spacer();Button("Done") { queueVisible = false } }
                List(transport.value.queue) { item in
                    HStack { Image(systemName:item.current ? "speaker.wave.2.fill" : "music.note").foregroundStyle(item.current ? .pink : .secondary);VStack(alignment:.leading) { Text(item.title);Text(item.artist).font(.caption).foregroundStyle(.secondary) } }
                }
            }.padding(22).frame(width:620,height:420).preferredColorScheme(.dark)
        }
    }
}