/**
 * POST /api/coach/speak-cartesia
 * Cartesia Sonic-2 — schnellstes TTS (~75ms first-byte), native German.
 *
 * Returns audio/mpeg. Voice via runtimeConfig.cartesiaVoiceId
 * (Fallback `b9de4a89-2257-424b-94c2-db18ba68c81a` wenn unset).
 */
const FALLBACK_VOICE_ID = "b9de4a89-2257-424b-94c2-db18ba68c81a";

export default defineEventHandler(async (event) => {
  await requireUser(event);

  const body = await readBody(event);
  const { text } = body as { text: string };

  if (!text?.trim()) {
    throw createError({ statusCode: 400, message: "text fehlt" });
  }

  const config = useRuntimeConfig();
  const key =
    (config.cartesiaApiKey as string) || process.env.CARTESIA_API_KEY || "";
  const voiceId =
    (config.cartesiaVoiceId as string) ||
    process.env.CARTESIA_VOICE_ID ||
    FALLBACK_VOICE_ID;

  if (!key) {
    throw createError({
      statusCode: 503,
      message: "CARTESIA_API_KEY nicht konfiguriert",
    });
  }

  const upstream = await fetch("https://api.cartesia.ai/tts/bytes", {
    method: "POST",
    headers: {
      "X-API-Key": key,
      "Cartesia-Version": "2024-11-13",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      model_id: "sonic-2",
      transcript: text.slice(0, 4096),
      voice: { mode: "id", id: voiceId },
      output_format: {
        container: "mp3",
        sample_rate: 22050,
        bit_rate: 64000,
      },
      language: "de",
    }),
  });

  if (!upstream.ok || !upstream.body) {
    const err = await upstream.text().catch(() => "");
    console.error("[speak-cartesia] error:", upstream.status, err);
    throw createError({
      statusCode: 502,
      message: "Cartesia TTS fehlgeschlagen",
    });
  }

  setHeader(event, "Content-Type", "audio/mpeg");
  setHeader(event, "Cache-Control", "no-store");

  const { Readable } = await import("node:stream");
  const nodeStream = Readable.fromWeb(upstream.body as never);
  return sendStream(event, nodeStream);
});