feat: add OpenRouter dictation and speech recognition settings

src/server/stt.ts

@@ -0,0 +1,75 @@
+import { OPENROUTER_STT_MODEL, STT_MAX_AUDIO_BYTES, STT_SAMPLE_RATE, WAV_HEADER_BYTES } from "../core/stt.ts";
+import { isSttLanguage } from "../core/i18n.ts";
+import { keyValue } from "./keys.ts";
+
+const fail = (status: number, message: string) => Response.json({ message }, { status });
+
+/** One complete recording per request. Credentials and audio never go to disk. */
+export async function openRouterTranscription(request: Request, key = keyValue("OPENROUTER_API_KEY")): Promise<Response> {
+	if (!key) return fail(503, "Dictation needs an OpenRouter key");
+	const params = new URL(request.url).searchParams;
+	if (params.get("model") !== OPENROUTER_STT_MODEL) return fail(400, "Unknown speech recognition model");
+	const language = params.get("language");
+	if (!isSttLanguage(language)) return fail(400, "Invalid speech recognition language");
+	if (request.headers.get("content-type") !== "audio/wav") return fail(415, "Invalid dictation audio");
+	if (Number(request.headers.get("content-length")) > STT_MAX_AUDIO_BYTES) return fail(413, "Recording exceeds OpenRouter's 25 MB audio limit");
+	if (!request.body) return fail(400, "Invalid dictation audio");
+	const reader = request.body.getReader();
+	const frames: Uint8Array[] = [];
+	let size = 0;
+	try {
+		while (true) {
+			const { done, value } = await reader.read();
+			if (done) break;
+			size += value.byteLength;
+			if (size > STT_MAX_AUDIO_BYTES) {
+				await reader.cancel();
+				return fail(413, "Recording exceeds OpenRouter's 25 MB audio limit");
+			}
+			frames.push(value);
+		}
+	} catch {
+		return fail(request.signal.aborted ? 499 : 400, "Could not read dictation audio");
+	} finally { reader.releaseLock(); }
+	if (request.signal.aborted) return fail(499, "Transcription cancelled");
+	const audio = Buffer.concat(frames, size);
+	// Accept exactly the lossless PCM container produced by our capture graph.
+	if (size <= WAV_HEADER_BYTES || size % 2 !== 0 || audio.toString("ascii", 0, 4) !== "RIFF"
+		|| audio.toString("ascii", 8, 12) !== "WAVE" || audio.toString("ascii", 12, 16) !== "fmt "
+		|| audio.readUInt32LE(4) !== size - 8 || audio.readUInt32LE(16) !== 16 || audio.readUInt16LE(20) !== 1
+		|| audio.readUInt16LE(22) !== 1 || audio.readUInt32LE(24) !== STT_SAMPLE_RATE
+		|| audio.readUInt32LE(28) !== STT_SAMPLE_RATE * 2 || audio.readUInt16LE(32) !== 2 || audio.readUInt16LE(34) !== 16
+		|| audio.toString("ascii", 36, 40) !== "data" || audio.readUInt32LE(40) !== size - WAV_HEADER_BYTES) {
+		return fail(400, "Invalid dictation audio");
+	}
+	const signal = AbortSignal.any([request.signal, AbortSignal.timeout(65_000)]);
+	try {
+		const response = await fetch("https://openrouter.ai/api/v1/audio/transcriptions", {
+			method: "POST",
+			headers: { Authorization: `Bearer ${key}`, "Content-Type": "application/json" },
+			body: JSON.stringify({
+				model: OPENROUTER_STT_MODEL,
+				input_audio: { data: audio.toString("base64"), format: "wav" },
+				// MAI allows one forced language; automatic detection supports mixed speech.
+				...(language === "multi" ? {} : { language }),
+				response_format: "json",
+			}),
+			signal,
+		});
+		if (!response.ok) {
+			// Provider diagnostics can contain credentials or echoed audio. Return only app-authored errors.
+			await response.body?.cancel();
+			if (response.status === 401 || response.status === 403) return fail(502, "OpenRouter rejected the API key");
+			if (response.status === 402) return fail(502, "OpenRouter credits are insufficient");
+			if (response.status === 429) return fail(429, "OpenRouter rate limit reached; try again later");
+			return fail(502, `OpenRouter transcription failed (${response.status})`);
+		}
+		const result = await response.json() as { text?: unknown };
+		if (typeof result.text !== "string") return fail(502, "OpenRouter returned an invalid transcript");
+		return Response.json({ text: result.text });
+	} catch (error) {
+		if (request.signal.aborted) return fail(499, "Transcription cancelled");
+		if (signal.aborted || (error instanceof Error && error.name === "TimeoutError")) return fail(504, "OpenRouter transcription timed out");
+		return fail(502, "OpenRouter transcription is unavailable");
+	}
+}