import Foundation
import Speech
import AVFoundation

/// 「记录问诊」录音 + 端侧转写(2026-06-28)。
///
/// 与 `SpeechDictationService`(写日记口述,刻意**不落盘音频**)的区别:问诊要留一段可回放的录音,
/// 所以本服务在**同一个 AVAudioEngine tap** 里做两件事:
///   ① `request.append(buffer)` → SFSpeech 端侧流式转写(实时字幕,`requiresOnDeviceRecognition = true`,红线:识别不出设备);
///   ② `audioFile.write(buffer)` → 落一份 m4a(AAC)到 tmp,停止后由调用方 `FileVault.importFile` 搬进加密 Vault。
///
/// 音频落盘是**尽力而为**:任何一步失败都 `try?` 吞掉,最坏情况只是没有录音文件——
/// 转写稿来自独立的 SFSpeech 流,照常返回,记录照常保存(守红线 #5:失败回退,不卡死)。
///
/// 工程默认 MainActor 隔离,本类型即 MainActor;tap 与识别回调在系统线程,
/// 闭包内只碰局部捕获对象,回主线程统一走 `Task { @MainActor }`(同 SpeechDictationService)。
final class ConsultationRecorder {

    enum RecorderError: Error, LocalizedError {
        case unavailable
        case audioEngineStartFailed(String)

        var errorDescription: String? {
            switch self {
            case .unavailable:
                return String(appLoc: "本机不支持端侧语音识别")
            case .audioEngineStartFailed(let m):
                return String(appLoc: "录音启动失败:\(m)")
            }
        }
    }

    /// 停止后返回:最终转写稿 + 录音临时文件(可能为 nil,音频落盘失败时)。
    struct Result {
        let transcript: String
        /// tmp 目录里的 m4a;调用方负责 `FileVault.importFile` 搬进 Vault 或丢弃。
        let audioTempURL: URL?
    }

    /// 优先系统语言;系统语言不支持端侧时兜底中文(同 SpeechDictationService)。
    private static func makeRecognizer() -> SFSpeechRecognizer? {
        if let r = SFSpeechRecognizer(locale: .current), r.supportsOnDeviceRecognition {
            return r
        }
        if let r = SFSpeechRecognizer(locale: Locale(identifier: "zh-CN")),
           r.supportsOnDeviceRecognition {
            return r
        }
        return nil
    }

    /// 本机是否支持端侧识别。false(模拟器 / 老机型)时 UI 退化为手动文字录入。
    static var isAvailable: Bool { makeRecognizer() != nil }

    private let audioEngine = AVAudioEngine()
    private var request: SFSpeechAudioBufferRecognitionRequest?
    private var task: SFSpeechRecognitionTask?
    /// 第一帧 buffer 到达时按其真实格式惰性建文件,保证写入格式与 tap 完全一致(不会因格式不匹配静默丢音)。
    private var audioFile: AVAudioFile?
    private var audioTempURL: URL?

    private var latestText = ""
    private var didFinish = false

    private(set) var isRecording = false

    /// 麦克风 + 语音识别两个权限一起申请。任一被拒返回 false。
    func requestAuthorization() async -> Bool {
        let speech = await withCheckedContinuation { (c: CheckedContinuation<SFSpeechRecognizerAuthorizationStatus, Never>) in
            SFSpeechRecognizer.requestAuthorization { c.resume(returning: $0) }
        }
        guard speech == .authorized else { return false }
        return await AVAudioApplication.requestRecordPermission()
    }

    /// 开始录音 + 流式识别。partial 结果在主线程回调(实时字幕)。
    func start(onPartial: @escaping (String) -> Void) throws {
        guard !isRecording else { return }
        guard let recognizer = Self.makeRecognizer(), recognizer.isAvailable else {
            throw RecorderError.unavailable
        }

        let session = AVAudioSession.sharedInstance()
        do {
            // .record + 默认模式(非 .measurement):问诊录音要尽量保真,不做语音增强裁剪。
            try session.setCategory(.record, mode: .default, options: .duckOthers)
            try session.setActive(true, options: .notifyOthersOnDeactivation)
        } catch {
            throw RecorderError.audioEngineStartFailed(error.localizedDescription)
        }

        let request = SFSpeechAudioBufferRecognitionRequest()
        request.requiresOnDeviceRecognition = true   // 红线:识别不出设备
        request.shouldReportPartialResults = true
        request.addsPunctuation = true
        self.request = request
        latestText = ""
        didFinish = false
        audioFile = nil

        // 录音先落 tmp(不加密、可边录边写,不受锁屏文件保护影响);停止后再搬进加密 Vault。
        let tempURL = FileManager.default.temporaryDirectory
            .appendingPathComponent("consult-\(UUID().uuidString).m4a")
        self.audioTempURL = tempURL

        let input = audioEngine.inputNode
        let format = input.outputFormat(forBus: 0)
        // 录音文件在装 tap 前就按 tap 格式建好:AAC 文件的 processingFormat = 该采样率/声道的 float 格式,
        // 正是 tap buffer 的格式 → write 不会因格式不符静默丢音。建失败(try? 为 nil)只是没录音文件,转写照常(尽力而为)。
        let settings: [String: Any] = [
            AVFormatIDKey: kAudioFormatMPEG4AAC,
            AVSampleRateKey: format.sampleRate,
            AVNumberOfChannelsKey: format.channelCount,
            AVEncoderAudioQualityKey: AVAudioQuality.medium.rawValue,
        ]
        let audioFile = try? AVAudioFile(forWriting: tempURL, settings: settings)
        self.audioFile = audioFile   // 留一份引用给 stop() flush
        // tap 在音频线程跑:只碰**局部捕获**的 request / audioFile,绝不碰 self(避免跨线程数据竞争,同 SpeechDictationService)。
        input.installTap(onBus: 0, bufferSize: 1024, format: format) { buffer, _ in
            request.append(buffer)
            try? audioFile?.write(from: buffer)
        }
        audioEngine.prepare()
        do {
            try audioEngine.start()
        } catch {
            input.removeTap(onBus: 0)
            deactivateSession()
            throw RecorderError.audioEngineStartFailed(error.localizedDescription)
        }

        task = recognizer.recognitionTask(with: request) { [weak self] result, error in
            Task { @MainActor in
                guard let self else { return }
                if let result {
                    self.latestText = result.bestTranscription.formattedString
                    onPartial(self.latestText)
                    if result.isFinal { self.didFinish = true }
                }
                if error != nil { self.didFinish = true }
            }
        }
        isRecording = true
    }

    /// 停止录音,等待最终识别结果(最多 1.5s,超时用最新 partial),返回转写稿 + 录音文件。
    func stop() async -> Result {
        guard isRecording else {
            return Result(transcript: latestText, audioTempURL: finishedAudioURL())
        }
        isRecording = false

        audioEngine.stop()
        audioEngine.inputNode.removeTap(onBus: 0)
        request?.endAudio()

        let deadline = Date().addingTimeInterval(1.5)
        while !didFinish && Date() < deadline {
            try? await Task.sleep(nanoseconds: 100_000_000)
        }
        task?.cancel()
        task = nil
        request = nil
        let url = finishedAudioURL()   // 关文件(置 nil)后再取 URL,确保已 flush 落盘
        deactivateSession()
        return Result(transcript: latestText, audioTempURL: url)
    }

    /// 用户直接关闭时的清理:不关心结果,立即停;顺手删掉半截录音临时文件。
    func abort() {
        guard isRecording else {
            cleanupTempFile()
            return
        }
        isRecording = false
        audioEngine.stop()
        audioEngine.inputNode.removeTap(onBus: 0)
        request?.endAudio()
        task?.cancel()
        task = nil
        request = nil
        audioFile = nil
        deactivateSession()
        cleanupTempFile()
    }

    /// 关掉写文件句柄(flush),返回有内容的录音 URL;文件没建成/为空则返回 nil。
    private func finishedAudioURL() -> URL? {
        audioFile = nil   // 释放写句柄,数据 flush 到磁盘
        guard let url = audioTempURL,
              let attrs = try? FileManager.default.attributesOfItem(atPath: url.path),
              let bytes = attrs[.size] as? Int, bytes > 0 else {
            return nil
        }
        return url
    }

    private func cleanupTempFile() {
        if let url = audioTempURL { try? FileManager.default.removeItem(at: url) }
        audioTempURL = nil
    }

    private func deactivateSession() {
        try? AVAudioSession.sharedInstance().setActive(false, options: .notifyOthersOnDeactivation)
    }
}