import { NextResponse } from "next/server";
import { promises as fs } from "fs";
import path from "path";
import { randomUUID } from "crypto";

const UPLOAD_DIR = path.join(process.cwd(), "public", "nano-banana", "uploads");
const MAX_FILE_SIZE_BYTES = 10 * 1024 * 1024; // 10MB
const ALLOWED_MIME = new Set(["image/png", "image/jpeg", "image/webp"]);

function getExtension(file: File) {
  const fromType =
    file.type === "image/png"
      ? "png"
      : file.type === "image/jpeg"
        ? "jpg"
        : file.type === "image/webp"
          ? "webp"
          : null;

  if (fromType) return fromType;

  const ext = path.extname(file.name).replace(".", "");
  if (ext) return ext;
  return "png";
}

export async function POST(req: Request) {
  try {
    const formData = await req.formData();
    const file = formData.get("file");

    if (!(file instanceof File)) {
      return NextResponse.json({ message: "File is required." }, { status: 400 });
    }

    if (!ALLOWED_MIME.has(file.type)) {
      return NextResponse.json({ message: "Unsupported file type." }, { status: 415 });
    }

    if (file.size > MAX_FILE_SIZE_BYTES) {
      return NextResponse.json({ message: "File is too large." }, { status: 413 });
    }

    await fs.mkdir(UPLOAD_DIR, { recursive: true });

    const filename = `${randomUUID()}.${getExtension(file)}`;
    const filePath = path.join(UPLOAD_DIR, filename);
    const buffer = Buffer.from(await file.arrayBuffer());

    await fs.writeFile(filePath, buffer);

    const relativePath = `/nano-banana/uploads/${filename}`;
    const host = req.headers.get("x-forwarded-host") ?? req.headers.get("host");
    const protocol = req.headers.get("x-forwarded-proto") ?? (host?.includes("localhost") ? "http" : "https");
    const origin = host ? `${protocol}://${host}` : "";
    const url = origin ? new URL(relativePath, origin).toString() : relativePath;

    return NextResponse.json({ url }, { status: 201 });
  } catch (error) {
    console.error(error);
    return NextResponse.json({ message: "Failed to upload file." }, { status: 500 });
  }
}