voicediary/VoiceDiary/Services/TranscriptionService.swift

import Foundation
import Speech

@Observable
final class TranscriptionService {
	var authorizationStatus: SFSpeechRecognizerAuthorizationStatus = .notDetermined

	private let speechRecognizer = SFSpeechRecognizer(locale: Locale(identifier: "de-DE"))

	func requestAuthorization() async {
		authorizationStatus = await withCheckedContinuation { continuation in
			SFSpeechRecognizer.requestAuthorization { status in
				continuation.resume(returning: status)
			}
		}
	}

	func transcribe(audioURL: URL) async throws -> String {
		guard let speechRecognizer, speechRecognizer.isAvailable else {
			throw TranscriptionError.recognizerUnavailable
		}

		let request = SFSpeechURLRecognitionRequest(url: audioURL)
		request.requiresOnDeviceRecognition = true
		request.shouldReportPartialResults = false
		request.addsPunctuation = true

		let result = try await speechRecognizer.recognitionTask(with: request)
		return result.bestTranscription.formattedString
	}
}

enum TranscriptionError: LocalizedError {
	case recognizerUnavailable
	case noResult

	var errorDescription: String? {
		switch self {
		case .recognizerUnavailable:
			String(localized: "transcription.error.unavailable")
		case .noResult:
			String(localized: "transcription.error.noResult")
		}
	}
}

private extension SFSpeechRecognizer {
	func recognitionTask(with request: SFSpeechRecognitionRequest) async throws -> SFSpeechRecognitionResult {
		try await withCheckedThrowingContinuation { continuation in
			recognitionTask(with: request) { result, error in
				if let error {
					continuation.resume(throwing: error)
				} else if let result, result.isFinal {
					continuation.resume(returning: result)
				}
			}
		}
	}
}