import SwiftUI
import AVFoundation

// MARK: - ViewModel

@Observable
@MainActor
final class PodcastPlayerViewModel {
    enum Phase {
        case generating(progress: Double, label: String)
        case downloading
        case ready(title: String)
        case failed(String)
    }

    var phase: Phase = .generating(progress: 0, label: "Starting…")
    var player: AVPlayer?
    var isPlaying = false
    var currentTime: Double = 0
    var duration: Double = 1

    private var pollingTask: Task<Void, Never>?
    private var timeObserver: Any?

    func start(articleUrl: String, claude: ClaudeService) {
        pollingTask = Task {
            do {
                let jobId = try await claude.generatePodcast(url: articleUrl)
                while !Task.isCancelled {
                    let job = try await claude.podcastStatus(jobId: jobId)
                    phase = .generating(
                        progress: Double(job.progress) / 100,
                        label: Self.statusLabel(job.status)
                    )
                    if job.isDone {
                        phase = .downloading
                        let audioUrl = try await claude.downloadPodcastAudio(jobId: jobId)
                        setupPlayer(url: audioUrl, title: job.title ?? "Podcast")
                        return
                    }
                    if job.isFailed {
                        phase = .failed(job.error ?? "Generation failed")
                        return
                    }
                    try await Task.sleep(for: .seconds(3))
                }
            } catch is CancellationError {
                // sheet dismissed — clean exit
            } catch {
                phase = .failed(error.localizedDescription)
            }
        }
    }

    func togglePlayPause() {
        guard let player else { return }
        if isPlaying { player.pause() } else { player.play() }
        isPlaying.toggle()
    }

    func seek(to time: Double) {
        player?.seek(to: CMTime(seconds: time, preferredTimescale: 600))
        currentTime = time
    }

    func teardown() {
        pollingTask?.cancel()
        player?.pause()
        if let obs = timeObserver { player?.removeTimeObserver(obs) }
        player = nil
    }

    private func setupPlayer(url: URL, title: String) {
        let item = AVPlayerItem(url: url)
        let p = AVPlayer(playerItem: item)
        player = p
        Task {
            if let d = try? await item.asset.load(.duration), d.isNumeric {
                duration = max(d.seconds, 1)
            }
        }
        let interval = CMTime(seconds: 0.5, preferredTimescale: 600)
        timeObserver = p.addPeriodicTimeObserver(forInterval: interval, queue: .main) { [weak self] t in
            self?.currentTime = t.seconds
        }
        phase = .ready(title: title)
    }

    private static func statusLabel(_ status: String) -> String {
        switch status {
        case "queued":    return "Queued…"
        case "fetching":  return "Fetching article…"
        case "scripting": return "Writing dialogue…"
        case "recording": return "Recording voices…"
        case "mixing":    return "Mixing audio…"
        default:          return "Generating…"
        }
    }
}

// MARK: - View

struct PodcastPlayerView: View {
    let articleUrl: String
    let claude: ClaudeService

    @Environment(\.dismiss) private var dismiss
    @State private var vm = PodcastPlayerViewModel()

    var body: some View {
        NavigationStack {
            VStack {
                Spacer()
                phaseContent
                Spacer()
            }
            .padding(.horizontal, 32)
            .navigationTitle("Podcast")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .topBarLeading) {
                    Button("Done") { dismiss() }
                }
            }
        }
        .onAppear { vm.start(articleUrl: articleUrl, claude: claude) }
        .onDisappear { vm.teardown() }
    }

    @ViewBuilder
    private var phaseContent: some View {
        switch vm.phase {
        case .generating(let progress, let label):
            generatingView(progress: progress, label: label)
        case .downloading:
            generatingView(progress: 1.0, label: "Preparing audio…")
        case .ready(let title):
            playerView(title: title)
        case .failed(let message):
            failedView(message: message)
        }
    }

    private func generatingView(progress: Double, label: String) -> some View {
        VStack(spacing: 28) {
            Image(systemName: "waveform")
                .font(.system(size: 52))
                .foregroundStyle(.secondary)
                .symbolEffect(.variableColor.iterative, isActive: true)

            VStack(spacing: 10) {
                ProgressView(value: progress)
                    .progressViewStyle(.linear)
                    .tint(.blue)
                Text(label)
                    .font(.system(size: 14))
                    .foregroundStyle(.secondary)
            }
        }
    }

    private func playerView(title: String) -> some View {
        VStack(spacing: 28) {
            RoundedRectangle(cornerRadius: 20)
                .fill(Color(.systemGray6))
                .frame(width: 220, height: 220)
                .overlay {
                    Image(systemName: "waveform.circle.fill")
                        .font(.system(size: 80))
                        .foregroundStyle(.blue)
                }

            Text(title)
                .font(.system(size: 18, weight: .semibold))
                .multilineTextAlignment(.center)
                .lineLimit(3)

            VStack(spacing: 6) {
                Slider(
                    value: Binding(get: { vm.currentTime }, set: { vm.seek(to: $0) }),
                    in: 0...vm.duration
                )
                .tint(.primary)

                HStack {
                    Text(formatTime(vm.currentTime))
                    Spacer()
                    Text(formatTime(vm.duration))
                }
                .font(.system(size: 12, design: .monospaced))
                .foregroundStyle(.tertiary)
            }

            Button { vm.togglePlayPause() } label: {
                Image(systemName: vm.isPlaying ? "pause.circle.fill" : "play.circle.fill")
                    .font(.system(size: 72))
                    .foregroundStyle(.primary)
            }
        }
    }

    private func failedView(message: String) -> some View {
        VStack(spacing: 16) {
            Image(systemName: "exclamationmark.triangle")
                .font(.system(size: 44))
                .foregroundStyle(.red)
            Text("Generation Failed")
                .font(.headline)
            Text(message)
                .font(.system(size: 14))
                .foregroundStyle(.secondary)
                .multilineTextAlignment(.center)
        }
    }

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