import { NextRequest, NextResponse } from 'next/server';
import { readFile } from 'fs/promises';
import { existsSync } from 'fs';
import path from 'path';

const UPLOAD_DIR = process.env.UPLOAD_DIR || '/app/uploads';

const MIME_TYPES: Record<string, string> = {
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.png': 'image/png',
  '.gif': 'image/gif',
  '.webp': 'image/webp',
  '.svg': 'image/svg+xml',
  '.avif': 'image/avif',
  '.pdf': 'application/pdf',
  '.txt': 'text/plain',
  '.md': 'text/markdown',
  '.csv': 'text/csv',
  '.json': 'application/json',
  '.xml': 'application/xml',
  '.zip': 'application/zip',
  '.gz': 'application/gzip',
  '.js': 'text/javascript',
  '.ts': 'text/typescript',
  '.html': 'text/html',
  '.css': 'text/css',
  '.py': 'text/x-python',
};

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

    // Validate filename (no path traversal)
    if (filename.includes('/') || filename.includes('\\') || filename.includes('..')) {
      return NextResponse.json({ error: 'Invalid filename' }, { status: 400 });
    }

    const filePath = path.join(UPLOAD_DIR, filename);

    // Validate resolved path stays within UPLOAD_DIR
    const resolvedPath = path.resolve(filePath);
    if (!resolvedPath.startsWith(path.resolve(UPLOAD_DIR))) {
      return NextResponse.json({ error: 'Invalid filename' }, { status: 400 });
    }

    if (!existsSync(filePath)) {
      return NextResponse.json({ error: 'File not found' }, { status: 404 });
    }

    const data = await readFile(filePath);
    const ext = path.extname(filename).toLowerCase();
    const contentType = MIME_TYPES[ext] || 'application/octet-stream';

    return new NextResponse(data, {
      headers: {
        'Content-Type': contentType,
        'Cache-Control': 'public, max-age=31536000, immutable',
        'Content-Length': data.length.toString(),
      },
    });
  } catch (error) {
    console.error('Serve file error:', error);
    return NextResponse.json({ error: 'Failed to serve file' }, { status: 500 });
  }
}