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import type {
TranscriptionLanguage,
TranscriptionResult,
TranscriptionProgress,
TranscriptionModelId,
} from "@/lib/transcription/types";
import {
DEFAULT_TRANSCRIPTION_MODEL,
TRANSCRIPTION_MODELS,
} from "@/constants/transcription-constants";
import type { WorkerMessage, WorkerResponse } from "./worker";
type ProgressCallback = (progress: TranscriptionProgress) => void;
class TranscriptionService {
private worker: Worker | null = null;
private currentModelId: TranscriptionModelId | null = null;
private isInitialized = false;
private isInitializing = false;
async transcribe({
audioData,
language = "auto",
modelId = DEFAULT_TRANSCRIPTION_MODEL,
onProgress,
}: {
audioData: Float32Array;
language?: TranscriptionLanguage;
modelId?: TranscriptionModelId;
onProgress?: ProgressCallback;
}): Promise<TranscriptionResult> {
await this.ensureWorker({ modelId, onProgress });
return new Promise((resolve, reject) => {
if (!this.worker) {
reject(new Error("Worker not initialized"));
return;
}
const handleMessage = (event: MessageEvent<WorkerResponse>) => {
const response = event.data;
switch (response.type) {
case "transcribe-progress":
onProgress?.({
status: "transcribing",
progress: response.progress,
message: "Transcribing audio...",
});
break;
case "transcribe-complete":
this.worker?.removeEventListener("message", handleMessage);
resolve({
text: response.text,
segments: response.segments,
language,
});
break;
case "transcribe-error":
this.worker?.removeEventListener("message", handleMessage);
reject(new Error(response.error));
break;
case "cancelled":
this.worker?.removeEventListener("message", handleMessage);
reject(new Error("Transcription cancelled"));
break;
}
};
this.worker.addEventListener("message", handleMessage);
this.worker.postMessage({
type: "transcribe",
audio: audioData,
language,
} satisfies WorkerMessage);
});
}
cancel() {
this.worker?.postMessage({ type: "cancel" } satisfies WorkerMessage);
}
private async ensureWorker({
modelId,
onProgress,
}: {
modelId: TranscriptionModelId;
onProgress?: ProgressCallback;
}): Promise<void> {
const needsNewModel = this.currentModelId !== modelId;
if (this.worker && this.isInitialized && !needsNewModel) {
return;
}
if (this.isInitializing && !needsNewModel) {
await this.waitForInit();
return;
}
this.terminate();
this.isInitializing = true;
this.isInitialized = false;
const model = TRANSCRIPTION_MODELS.find((m) => m.id === modelId);
if (!model) {
throw new Error(`Unknown model: ${modelId}`);
}
this.worker = new Worker(new URL("./worker.ts", import.meta.url), {
type: "module",
});
return new Promise((resolve, reject) => {
if (!this.worker) {
reject(new Error("Failed to create worker"));
return;
}
const handleMessage = (event: MessageEvent<WorkerResponse>) => {
const response = event.data;
switch (response.type) {
case "init-progress":
onProgress?.({
status: "loading-model",
progress: response.progress,
message: `Loading ${model.name} model...`,
});
break;
case "init-complete":
this.worker?.removeEventListener("message", handleMessage);
this.isInitialized = true;
this.isInitializing = false;
this.currentModelId = modelId;
resolve();
break;
case "init-error":
this.worker?.removeEventListener("message", handleMessage);
this.isInitializing = false;
this.terminate();
reject(new Error(response.error));
break;
}
};
this.worker.addEventListener("message", handleMessage);
this.worker.postMessage({
type: "init",
modelId: model.huggingFaceId,
} satisfies WorkerMessage);
});
}
private waitForInit(): Promise<void> {
return new Promise((resolve) => {
const checkInit = () => {
if (this.isInitialized) {
resolve();
} else if (!this.isInitializing) {
resolve();
} else {
setTimeout(checkInit, 100);
}
};
checkInit();
});
}
terminate() {
this.worker?.terminate();
this.worker = null;
this.isInitialized = false;
this.isInitializing = false;
this.currentModelId = null;
}
}
export const transcriptionService = new TranscriptionService();
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