import { NextResponse } from "next/server";

export const runtime = "nodejs";

export async function POST(req: Request) {
  try {
    // 1) env check
    const uploadUrl = process.env.CDN_UPLOAD_URL;
    const token = process.env.CDN_SERVICE_TOKEN;

    if (!uploadUrl) {
      return NextResponse.json(
        { error: "Missing env: CDN_UPLOAD_URL" },
        { status: 500 },
      );
    }
    if (!token) {
      return NextResponse.json(
        { error: "Missing env: CDN_SERVICE_TOKEN" },
        { status: 500 },
      );
    }

    // 2) read multipart
    const incoming = await req.formData();
    const file = incoming.get("file");

    if (!file) {
      return NextResponse.json(
        { error: "file is required (field name must be 'file')" },
        { status: 400 },
      );
    }

    // In Next route handlers, this should be a Web File
    if (!(file instanceof File)) {
      return NextResponse.json(
        {
          error: "Invalid file type",
          receivedType: Object.prototype.toString.call(file),
        },
        { status: 400 },
      );
    }

    // 3) forward to CDN
    const fd = new FormData();
    fd.append("file", file, file.name);

    const cdnRes = await fetch(uploadUrl, {
      method: "POST",
      headers: {
        Authorization: `Bearer ${token}`,
      },
      body: fd,
    });

    const contentType = cdnRes.headers.get("content-type") || "";
    const isJson = contentType.includes("application/json");

    const payload = isJson ? await cdnRes.json() : await cdnRes.text();

    if (!cdnRes.ok) {
      return NextResponse.json(
        {
          error: "CDN upload failed",
          status: cdnRes.status,
          payload,
        },
        { status: cdnRes.status },
      );
    }

    return NextResponse.json(payload);
  } catch (e: unknown) {
    // 4) robust error serialization (no toString on undefined)
    let details = "unknown error";
    if (e instanceof Error) details = e.message;
    else if (typeof e === "string") details = e;
    else {
      try {
        details = JSON.stringify(e);
      } catch {
        details = "non-serializable error";
      }
    }

    return NextResponse.json(
      { error: "Unexpected error", details },
      { status: 500 },
    );
  }
}