import AVFoundation
#if os(macOS)
import AppKit

/// 视频源录制器：从 AVPlayerItemVideoOutput 抓帧 + 源 URL 音频轨道，写入 mp4
@MainActor
final class PlayerRecorder: NSObject {
    
    private var writer: AVAssetWriter?
    private var videoInput: AVAssetWriterInput?
    private var audioInput: AVAssetWriterInput?
    private var timer: Timer?
    private var startDate: Date?
    private var weakOutput: AVPlayerItemVideoOutput?
    nonisolated(unsafe) private var isRunning = false
    
    // 视频：缓存上一帧，确保静态场景也能持续写入
    private var lastPixelBuffer: CVPixelBuffer?
    private var captureFrameCount: Int = 0
    
    // 音频
    private var audioReader: AVAssetReader?
    private var audioReaderOutput: AVAssetReaderTrackOutput?
    private nonisolated(unsafe) var audioFeedTimer: DispatchSourceTimer?
    
    // 共享时间基准：player.currentTime() at record start
    nonisolated(unsafe) private var recordStartTime: CMTime = .zero
    nonisolated(unsafe) private var audioStartHostTime: CFTimeInterval = 0
    nonisolated(unsafe) private var pendingAudioSample: CMSampleBuffer?
    
    @Published var isRecording = false
    @Published var durationText = "00:00"
    
    var onRecordingSaved: ((URL) -> Void)?
    var onError: ((String) -> Void)?
    
    private var tempURL: URL?
    
    private var saveDirectory: URL {
        let movies = FileManager.default.urls(for: .moviesDirectory, in: .userDomainMask).first!
        let dir = movies.appendingPathComponent("MiniPlayer", isDirectory: true)
        try? FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
        return dir
    }
    
    // MARK: - 开始录制
    func startRecording(from output: AVPlayerItemVideoOutput, sourceURL: URL, startTime: CMTime) {
        guard !isRecording else { return }
        
        weakOutput = output
        lastPixelBuffer = nil
        captureFrameCount = 0
        isRunning = false
        recordStartTime = startTime  // 共享时间基准
        audioStartHostTime = 0
        pendingAudioSample = nil
        
        // 临时文件
        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy-MM-dd_HH-mm-ss"
        let filename = "Recording_\(formatter.string(from: Date())).mp4"
        let url = saveDirectory.appendingPathComponent(filename)
        tempURL = url
        
        do {
            writer = try AVAssetWriter(outputURL: url, fileType: .mp4)
        } catch {
            onError?("Cannot create writer: \(error.localizedDescription)")
            return
        }
        
        guard let writer = writer else { return }
        
        // 视频输入
        let videoSettings: [String: Any] = [
            AVVideoCodecKey: AVVideoCodecType.h264,
            AVVideoWidthKey: 1920,
            AVVideoHeightKey: 1080
        ]
        let vInput = AVAssetWriterInput(mediaType: .video, outputSettings: videoSettings)
        vInput.expectsMediaDataInRealTime = true
        if writer.canAdd(vInput) {
            writer.add(vInput)
            videoInput = vInput
        }
        
        // 音频输入
        let audioSettings: [String: Any] = [
            AVFormatIDKey: kAudioFormatMPEG4AAC,
            AVSampleRateKey: 44100,
            AVNumberOfChannelsKey: 2,
            AVEncoderBitRateKey: 128000
        ]
        let aInput = AVAssetWriterInput(mediaType: .audio, outputSettings: audioSettings)
        aInput.expectsMediaDataInRealTime = true
        if writer.canAdd(aInput) {
            writer.add(aInput)
            audioInput = aInput
        }
        
        let success = writer.startWriting()
        if !success {
            print("[Recorder] startWriting failed: \(writer.error?.localizedDescription ?? "unknown")")
            onError?("Cannot start writer: \(writer.error?.localizedDescription ?? "unknown")")
            return
        }
        
        // session 起点为 0，视频和音频都用相对时间戳
        writer.startSession(atSourceTime: .zero)
        print("[Recorder] Writer started, session at .zero")
        
        // 启动视频抓帧
        isRecording = true
        isRunning = true
        startTimer()
        startCaptureLoop()
        
        // 启动音频读取
        startAudioCapture(sourceURL: sourceURL, startTime: startTime, audioWriterInput: aInput)
    }
    
    // MARK: - 停止录制
    func stopRecording() {
        guard isRecording else { return }
        isRecording = false
        isRunning = false
        captureTimer?.invalidate()
        captureTimer = nil
        stopTimer()
        
        // 停止音频 timer
        audioFeedTimer?.cancel()
        audioFeedTimer = nil
        
        // 停止音频 reader
        audioReader?.cancelReading()
        audioReader = nil
        audioReaderOutput = nil
        pendingAudioSample = nil
        
        videoInput?.markAsFinished()
        audioInput?.markAsFinished()
        
        writer?.finishWriting { [weak self] in
            Task { @MainActor in
                guard let self = self, let w = self.writer else { return }
                let count = self.captureFrameCount
                print("[Recorder] finishWriting status: \(w.status.rawValue), error: \(w.error?.localizedDescription ?? "none"), frames: \(count)")
                if w.status == .completed, let url = self.tempURL {
                    self.showSaveDialog(tempURL: url)
                } else {
                    self.onError?("Recording failed: \(w.error?.localizedDescription ?? "unknown (status=\(w.status.rawValue))")")
                    if let url = self.tempURL {
                        try? FileManager.default.removeItem(at: url)
                    }
                }
            }
        }
        
        lastPixelBuffer = nil
    }
    
    // MARK: - 视频抓帧 (30fps Timer)
    private var captureTimer: Timer?
    
    private func startCaptureLoop() {
        captureTimer = Timer.scheduledTimer(withTimeInterval: 1.0 / 30.0, repeats: true) { [weak self] _ in
            Task { @MainActor in
                self?.captureVideoFrame()
            }
        }
    }
    
    private func captureVideoFrame() {
        guard isRunning, let output = weakOutput, let input = videoInput,
              input.isReadyForMoreMediaData else { return }
        
        let hostTime = CACurrentMediaTime()
        let itemTime = output.itemTime(forHostTime: hostTime)
        
        // 尝试获取新帧，否则复用上一帧
        if let pb = output.copyPixelBuffer(forItemTime: itemTime, itemTimeForDisplay: nil) {
            lastPixelBuffer = pb
        }
        
        guard let pb = lastPixelBuffer else { return }
        
        // 相对时间戳：itemTime - recordStartTime
        let relativeTime = CMTimeSubtract(itemTime, recordStartTime)
        guard relativeTime.seconds >= 0 else { return }
        
        let sampleBuffer = Self.createSampleBuffer(from: pb, time: relativeTime)
        if let sb = sampleBuffer {
            if input.append(sb) {
                captureFrameCount += 1
            }
        }
    }
    
    private static func createSampleBuffer(from pixelBuffer: CVPixelBuffer, time: CMTime) -> CMSampleBuffer? {
        var info = CMSampleTimingInfo()
        info.presentationTimeStamp = time
        info.duration = CMTime(value: 1, timescale: 30)
        info.decodeTimeStamp = .invalid
        
        var formatDescription: CMFormatDescription?
        CMVideoFormatDescriptionCreateForImageBuffer(allocator: kCFAllocatorDefault, imageBuffer: pixelBuffer, formatDescriptionOut: &formatDescription)
        
        guard let fd = formatDescription else { return nil }
        
        var sampleBuffer: CMSampleBuffer?
        CMSampleBufferCreateReadyWithImageBuffer(allocator: kCFAllocatorDefault, imageBuffer: pixelBuffer, formatDescription: fd, sampleTiming: &info, sampleBufferOut: &sampleBuffer)
        return sampleBuffer
    }
    
    // MARK: - 音频读取（DispatchSourceTimer 限速到实时）
    private func startAudioCapture(sourceURL: URL, startTime: CMTime, audioWriterInput: AVAssetWriterInput) {
        let asset = AVURLAsset(url: sourceURL)
        
        Task {
            do {
                let audioTracks = try await asset.loadTracks(withMediaType: .audio)
                guard let audioTrack = audioTracks.first else {
                    print("[Recorder] No audio track in source")
                    return
                }
                guard self.isRunning else { return }
                
                let reader = try AVAssetReader(asset: asset)
                let readerOutput = AVAssetReaderTrackOutput(track: audioTrack, outputSettings: [
                    AVFormatIDKey: kAudioFormatLinearPCM,
                    AVSampleRateKey: 44100,
                    AVNumberOfChannelsKey: 2,
                    AVLinearPCMBitDepthKey: 16,
                    AVLinearPCMIsFloatKey: false,
                    AVLinearPCMIsBigEndianKey: false,
                    AVLinearPCMIsNonInterleaved: false
                ])
                readerOutput.alwaysCopiesSampleData = false
                
                // 从播放位置开始读取
                reader.timeRange = CMTimeRange(start: startTime, duration: .positiveInfinity)
                
                if reader.canAdd(readerOutput) {
                    reader.add(readerOutput)
                    reader.startReading()
                    
                    self.audioReader = reader
                    self.audioReaderOutput = readerOutput
                    
                    // 记录 wall-clock 起始时间，用于实时限速
                    self.audioStartHostTime = CACurrentMediaTime()
                    
                    // 用 DispatchSourceTimer 每 20ms 喂一次音频，限速到实时
                    let queue = DispatchQueue(label: "recorder.audio.feed")
                    let feedTimer = DispatchSource.makeTimerSource(queue: queue)
                    feedTimer.schedule(deadline: .now() + .milliseconds(10), repeating: .milliseconds(20))
                    feedTimer.setEventHandler { [weak self] in
                        self?.feedAudioSamplesRealtime(writerInput: audioWriterInput,
                                                       readerOutput: readerOutput,
                                                       reader: reader)
                    }
                    self.audioFeedTimer = feedTimer
                    feedTimer.resume()
                }
            } catch {
                print("[Recorder] Audio capture setup failed: \(error)")
            }
        }
    }
    
    /// 每 20ms 调用，只写入不超过当前实时进度的音频
    private nonisolated func feedAudioSamplesRealtime(writerInput: AVAssetWriterInput,
                                                       readerOutput: AVAssetReaderTrackOutput,
                                                       reader: AVAssetReader) {
        guard isRunning, reader.status == .reading else {
            if isRunning && reader.status != .reading {
                writerInput.markAsFinished()
                audioFeedTimer?.cancel()
            }
            return
        }
        guard writerInput.isReadyForMoreMediaData else { return }
        
        // 实时进度：录制开始以来经过的秒数
        let elapsed = CACurrentMediaTime() - audioStartHostTime
        let maxAudioTime = elapsed + 0.05  // 允许 50ms 预读
        
        // 先处理上次缓存的超前 sample
        if let pending = pendingAudioSample {
            let pts = CMSampleBufferGetPresentationTimeStamp(pending)
            let relative = CMTimeSubtract(pts, recordStartTime)
            if relative.seconds > maxAudioTime {
                return  // 还没到时间，等下次 tick
            }
            pendingAudioSample = nil
            if let nb = Self.remapAudioBuffer(pending, offset: recordStartTime) {
                _ = writerInput.append(nb)
            }
        }
        
        // 继续读取，直到追上实时进度
        while isRunning, reader.status == .reading, writerInput.isReadyForMoreMediaData {
            guard let sampleBuffer = readerOutput.copyNextSampleBuffer() else {
                // 源文件音频读完
                if reader.status != .reading {
                    writerInput.markAsFinished()
                    audioFeedTimer?.cancel()
                }
                return
            }
            
            let pts = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
            let relative = CMTimeSubtract(pts, recordStartTime)
            
            // 超出实时进度 → 缓存，等下次 tick
            if relative.seconds > maxAudioTime {
                pendingAudioSample = sampleBuffer
                return
            }
            
            // 跳过负时间戳（音频 pts 在 recordStartTime 之前）
            guard relative.seconds >= 0 else { continue }
            
            if let nb = Self.remapAudioBuffer(sampleBuffer, offset: recordStartTime) {
                if !writerInput.append(nb) {
                    return
                }
            }
        }
    }
    
    /// 重映射音频 sample buffer 的时间戳为相对时间
    private nonisolated static func remapAudioBuffer(_ sampleBuffer: CMSampleBuffer, offset: CMTime) -> CMSampleBuffer? {
        var count: CMItemCount = 0
        CMSampleBufferGetSampleTimingInfoArray(sampleBuffer, entryCount: 0, arrayToFill: nil, entriesNeededOut: &count)
        guard count > 0 else { return sampleBuffer }
        
        var timingInfo = [CMSampleTimingInfo](repeating: CMSampleTimingInfo(), count: count)
        CMSampleBufferGetSampleTimingInfoArray(sampleBuffer, entryCount: count, arrayToFill: &timingInfo, entriesNeededOut: nil)
        
        for i in 0..<count {
            timingInfo[i].decodeTimeStamp = .invalid
            timingInfo[i].presentationTimeStamp = CMTimeSubtract(timingInfo[i].presentationTimeStamp, offset)
        }
        
        var newBuffer: CMSampleBuffer?
        CMSampleBufferCreateCopyWithNewTiming(allocator: kCFAllocatorDefault, sampleBuffer: sampleBuffer, sampleTimingEntryCount: count, sampleTimingArray: &timingInfo, sampleBufferOut: &newBuffer)
        return newBuffer
    }
    
    // MARK: - Timer (显示录制时长)
    private func startTimer() {
        startDate = Date()
        durationText = "00:00"
        timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { [weak self] _ in
            Task { @MainActor in
                guard let self = self, let start = self.startDate else { return }
                let elapsed = Int(Date().timeIntervalSince(start))
                let m = elapsed / 60
                let s = elapsed % 60
                let h = m / 60
                if h > 0 {
                    self.durationText = String(format: "%d:%02d:%02d", h, m % 60, s)
                } else {
                    self.durationText = String(format: "%02d:%02d", m, s)
                }
            }
        }
    }
    
    private func stopTimer() {
        timer?.invalidate()
        timer = nil
        startDate = nil
        durationText = "00:00"
    }
    
    // MARK: - 保存对话框
    private func showSaveDialog(tempURL: URL) {
        let panel = NSSavePanel()
        panel.nameFieldStringValue = tempURL.lastPathComponent
        panel.allowedContentTypes = [.mpeg4Movie]
        panel.directoryURL = saveDirectory
        panel.title = "Save Recording"
        
        panel.begin { [weak self] response in
            guard let self = self else { return }
            if response == .OK, let destURL = panel.url {
                do {
                    if FileManager.default.fileExists(atPath: destURL.path) {
                        try FileManager.default.removeItem(at: destURL)
                    }
                    try FileManager.default.moveItem(at: tempURL, to: destURL)
                    self.onRecordingSaved?(destURL)
                } catch {
                    self.onError?("Save failed: \(error.localizedDescription)")
                }
            } else {
                try? FileManager.default.removeItem(at: tempURL)
            }
        }
    }
}

#endif