MyApp/SpeechPromptService.swift

1import AVFoundation2import Synchronization3 4private final class SpeechAssetSink: Sendable {5    private struct State {6        var file: AVAudioFile?7        var continuation: CheckedContinuation<Void, Error>?8    }9    private let state: Mutex<State>10    let url: URL11    init(url: URL, continuation: CheckedContinuation<Void, Error>) {12        self.url = url13        state = Mutex(State(continuation: continuation))14    }15    func receive(_ buffer: AVAudioBuffer) {16        state.withLock { state in17            guard let continuation = state.continuation, let pcm = buffer as? AVAudioPCMBuffer else { return }18            do {19                if pcm.frameLength == 0 {20                    state.file = nil; state.continuation = nil21                    continuation.resume()22                } else {23                    if state.file == nil { state.file = try AVAudioFile(forWriting: url, settings: pcm.format.settings) }24                    try state.file?.write(from: pcm)25                }26            } catch {27                state.file = nil; state.continuation = nil28                continuation.resume(throwing: error)29            }30        }31    }32    func cancel() {33        state.withLock { state in34            state.file = nil35            state.continuation?.resume(throwing: CancellationError())36            state.continuation = nil37        }38    }39}40 41@MainActor42final class SpeechPromptService: NSObject, AVAudioPlayerDelegate {43    private let synthesizer = AVSpeechSynthesizer()44    private var player: AVAudioPlayer?45    private var sink: SpeechAssetSink?46    var rate: Float = AVSpeechUtteranceDefaultSpeechRate47    var voiceID: String?48    private(set) var playbackFinished: Bool?49    private(set) var playbackError: String?50 51    func prepare(_ text: String, to url: URL) async throws {52        let utterance = AVSpeechUtterance(string: text)53        utterance.voice = voiceID.flatMap(AVSpeechSynthesisVoice.init(identifier:)) ?? AVSpeechSynthesisVoice(language: "en-US")54        utterance.rate = rate55        try await withCheckedThrowingContinuation { (continuation: CheckedContinuation<Void, Error>) in56            let sink = SpeechAssetSink(url: url, continuation: continuation)57            self.sink = sink58            synthesizer.write(utterance) { buffer in sink.receive(buffer) }59        }60        try Task.checkCancellation()61        sink = nil62        player = try AVAudioPlayer(contentsOf: url)63        player?.delegate = self64        playbackFinished = nil; playbackError = nil65        guard player?.prepareToPlay() == true else { throw PartyError.message("Speech preparation failed.") }66    }67    func play() throws {68        guard player?.play() == true else { throw PartyError.message("Speech playback failed.") }69    }70    var isPlaying: Bool { player?.isPlaying == true }71    var duration: Double { player?.duration ?? 0 }72    func invalidatePreparedAudio() {73        stop()74        player = nil75    }76    func audioPlayerDidFinishPlaying(_ player: AVAudioPlayer, successfully flag: Bool) {77        playbackFinished = flag78    }79    func audioPlayerDecodeErrorDidOccur(_ player: AVAudioPlayer, error: Error?) {80        playbackError = error?.localizedDescription ?? "Speech playback failed."81        playbackFinished = false82    }83    func stop() {84        playbackFinished = false85        sink?.cancel(); sink = nil86        player?.stop()87        synthesizer.stopSpeaking(at: .immediate)88    }89}