import { NextRequest, NextResponse } from "next/server";
import fs from "fs";
import path from "path";

export async function GET(
  req: NextRequest,
  { params }: { params: { filename: string } }
) {
  try {
    const rawFilename = params.filename;

    // 1. Strict filename validation: alphanumeric + hyphens/underscores + safe image extensions only
    const validFilenameRegex = /^[a-zA-Z0-9_-]+\.(jpg|jpeg|png|webp)$/i;
    if (!rawFilename || !validFilenameRegex.test(rawFilename)) {
      return new NextResponse("Bad Request: Invalid or disallowed image filename", { status: 400 });
    }

    const filename = path.basename(rawFilename);
    const imagesDir = path.resolve(process.cwd(), "data", "images");
    const filePath = path.resolve(imagesDir, filename);

    // 2. Prevent path traversal outside data/images directory
    if (!filePath.startsWith(imagesDir)) {
      return new NextResponse("Access Denied", { status: 403 });
    }

    if (!fs.existsSync(filePath)) {
      return new NextResponse("Image Not Found", { status: 404 });
    }

    const fileBuffer = fs.readFileSync(filePath);
    const ext = path.extname(filename).toLowerCase();

    let contentType = "image/png";
    if (ext === ".jpg" || ext === ".jpeg") contentType = "image/jpeg";
    else if (ext === ".webp") contentType = "image/webp";

    return new NextResponse(fileBuffer, {
      status: 200,
      headers: {
        "Content-Type": contentType,
        "X-Content-Type-Options": "nosniff",
        "Content-Security-Policy": "default-src 'none'; sandbox",
        "Content-Disposition": `${req.nextUrl.searchParams.get("download") === "1" ? "attachment" : "inline"}; filename="${filename}"`,
        "Cache-Control": "public, max-age=31536000, immutable",
      },
    });
  } catch (error) {
    console.error("[API Image Serve] Error reading file:", error);
    return new NextResponse("Server Error", { status: 500 });
  }
}