web/src/app/api/speech-to-text/route.ts

import { NextResponse } from "next/server";

export async function POST(req: Request) {
  try {
    const formData = await req.formData();
    const audioFile = formData.get("audio") as Blob;

    if (!audioFile) {
      return NextResponse.json(
        { error: "Audio file is required" },
        { status: 400 }
      );
    }

    const MAX_UPLOAD_BYTES = 100 * 1024 * 1024; // 100MB
    if (audioFile.size > MAX_UPLOAD_BYTES) {
      return NextResponse.json(
        { error: `File size exceeds ${MAX_UPLOAD_BYTES / 1024 / 1024}MB limit` },
        { status: 413 }
      );
    }

    const MODAL_API_URL =
      process.env.MODAL_API_URL ??
      "https://yongkang-zou1999--evoxtral-api-evoxtralmodel-web.modal.run";

    // Forward the formData to the Modal API (non-streaming)
    const upstream = new FormData();
    const originalName = (audioFile as File).name || "audio.wav";
    upstream.append("file", audioFile, originalName);
    const response = await fetch(`${MODAL_API_URL}/transcribe`, {
      method: "POST",
      body: upstream,
      // Signal timeout after 5 minutes
      signal: AbortSignal.timeout(5 * 60 * 1000),
    });

    if (!response.ok) {
      const errorData = await response.json().catch(() => ({}));
      return NextResponse.json(
        { error: errorData.detail || "Transcription failed at Model layer" },
        { status: response.status }
      );
    }

    const data = await response.json();
    return NextResponse.json(data);
  } catch (error: any) {
    console.error("Transcription proxy error:", error);
    const isTimeout = error.name === "TimeoutError" || error.name === "AbortError";
    return NextResponse.json(
      { error: isTimeout ? "Transcription timed out" : "Internal server error connecting to model layer" },
      { status: isTimeout ? 504 : 500 }
    );
  }
}