A sketch of a transcription effect in TCA.

transcription_effect.swift

import ComposableArchitecture

let transcriptionEffect: (URL) -> Effect<String, NSError> = { audioURL in
	.future { callback in
		guard
			let speechRecognizer = SFSpeechRecognizer(),
			speechRecognizer.isAvailable // (1)
		else {
			callback(
				.failure(
					NSError(
						domain: "com.jasdev.CaptionsGeneration",
						code: 1,
						userInfo: nil
					)
				)
			)
			return
		}

		let request = SFSpeechURLRecognitionRequest(url: audioURL)
		request.shouldReportPartialResults = false // (2)

		speechRecognizer.recognitionTask(with: request) { [weak request] result, error in
			if let error = error {
				callback(.failure(error as NSError))
			} else {
				callback(
					.success(
						transcriptionSegmentsToSubRipText(
							result!
								.bestTranscription
								.segments
						)
					)
				)
			}
		}
	}
}