import { NextRequest, NextResponse } from 'next/server';

export const dynamic = 'force-dynamic';

function getCandidateUrls(filePath: string): string[] {
  const set = new Set<string>();

  if (process.env.INTERNAL_API_URL) {
    const base = process.env.INTERNAL_API_URL.replace(/\/api\/?$/, '');
    set.add(`${base}/uploads/${filePath}`);
  }

  if (process.env.NEXT_PUBLIC_API_URL && !process.env.NEXT_PUBLIC_API_URL.startsWith('/')) {
    const base = process.env.NEXT_PUBLIC_API_URL.replace(/\/api\/?$/, '');
    set.add(`${base}/uploads/${filePath}`);
  }

  // Production backend port and domains
  set.add(`http://127.0.0.1:4400/uploads/${filePath}`);
  set.add(`http://localhost:4400/uploads/${filePath}`);
  set.add(`http://127.0.0.1:4000/uploads/${filePath}`);
  set.add(`http://localhost:4000/uploads/${filePath}`);
  set.add(`https://api.canina.ir/uploads/${filePath}`);

  set.add(`http://backend_prod:3000/uploads/${filePath}`);
  set.add(`http://canino_backend_prod:3000/uploads/${filePath}`);
  set.add(`http://backend:3000/uploads/${filePath}`);

  set.add(`http://127.0.0.1:4001/uploads/${filePath}`);
  set.add(`http://localhost:4001/uploads/${filePath}`);

  return Array.from(set);
}

function getMimeType(filePath: string, fallback: string): string {
  const ext = filePath.split('.').pop()?.toLowerCase();
  switch (ext) {
    case 'webp': return 'image/webp';
    case 'jpg':
    case 'jpeg': return 'image/jpeg';
    case 'png': return 'image/png';
    case 'gif': return 'image/gif';
    case 'svg': return 'image/svg+xml';
    case 'avif': return 'image/avif';
    case 'mp4': return 'video/mp4';
    case 'webm': return 'video/webm';
    case 'mp3': return 'audio/mpeg';
    case 'pdf': return 'application/pdf';
    default: return fallback || 'application/octet-stream';
  }
}

export async function GET(
  request: NextRequest,
  { params }: { params: Promise<{ path: string[] }> }
) {
  try {
    const { path } = await params;
    if (!path || path.length === 0) {
      return new NextResponse('Bad Request: Missing file path', { status: 400 });
    }

    const rawFilePath = path.join('/');
    const filePath = path.map(segment => encodeURIComponent(segment)).join('/');
    const candidates = getCandidateUrls(filePath);

    // Forward streaming/caching headers from client
    const forwardedHeaders: HeadersInit = {};
    const rangeHeader = request.headers.get('range');
    if (rangeHeader) forwardedHeaders['range'] = rangeHeader;
    const ifNoneMatch = request.headers.get('if-none-match');
    if (ifNoneMatch) forwardedHeaders['if-none-match'] = ifNoneMatch;
    const ifModifiedSince = request.headers.get('if-modified-since');
    if (ifModifiedSince) forwardedHeaders['if-modified-since'] = ifModifiedSince;

    let backendRes: Response | null = null;

    for (const targetUrl of candidates) {
      try {
        const res = await fetch(targetUrl, {
          method: 'GET',
          headers: forwardedHeaders,
          cache: 'no-store',
        });

        if (res.ok || res.status === 304 || res.status === 206) {
          backendRes = res;
          break;
        }
      } catch {
        // Continue trying next candidate
      }
    }

    // If 304 received without body or if not found with conditional headers, retry unconditionally
    if (backendRes && backendRes.status === 304 && !backendRes.body) {
      for (const targetUrl of candidates) {
        try {
          const freshRes = await fetch(targetUrl, {
            method: 'GET',
            cache: 'no-store',
          });
          if (freshRes.ok) {
            backendRes = freshRes;
            break;
          }
        } catch {
          // Continue
        }
      }
    }

    if (!backendRes) {
      return new NextResponse('Media file not found upstream', { status: 404 });
    }

    const responseHeaders = new Headers();
    const rawContentType = backendRes.headers.get('content-type') || '';
    const contentType = getMimeType(rawFilePath, rawContentType);
    responseHeaders.set('Content-Type', contentType);

    const contentLength = backendRes.headers.get('content-length');
    if (contentLength) responseHeaders.set('Content-Length', contentLength);

    const contentRange = backendRes.headers.get('content-range');
    if (contentRange) responseHeaders.set('Content-Range', contentRange);

    const acceptRanges = backendRes.headers.get('accept-ranges') || 'bytes';
    responseHeaders.set('Accept-Ranges', acceptRanges);

    const etag = backendRes.headers.get('etag');
    if (etag) responseHeaders.set('ETag', etag);

    const lastModified = backendRes.headers.get('last-modified');
    if (lastModified) responseHeaders.set('Last-Modified', lastModified);

    responseHeaders.set('Cache-Control', 'public, max-age=31536000, s-maxage=31536000, immutable');
    responseHeaders.set('X-Content-Type-Options', 'nosniff');

    return new Response(backendRes.body, {
      status: backendRes.status,
      statusText: backendRes.statusText,
      headers: responseHeaders,
    });
  } catch (err: unknown) {
    console.error('[Media Proxy Error]', err);
    return new NextResponse('Internal Media Proxy Error', { status: 502 });
  }
}

export async function HEAD(
  request: NextRequest,
  { params }: { params: Promise<{ path: string[] }> }
) {
  try {
    const { path } = await params;
    if (!path || path.length === 0) {
      return new NextResponse(null, { status: 400 });
    }

    const filePath = path.map(segment => encodeURIComponent(segment)).join('/');
    const candidates = getCandidateUrls(filePath);

    let backendRes: Response | null = null;

    for (const targetUrl of candidates) {
      try {
        const res = await fetch(targetUrl, { method: 'HEAD', cache: 'no-store' });
        if (res.ok || res.status === 304) {
          backendRes = res;
          break;
        }
      } catch {
        // Continue
      }
    }

    if (!backendRes) {
      return new NextResponse(null, { status: 404 });
    }

    const responseHeaders = new Headers();
    const contentType = backendRes.headers.get('content-type') || 'application/octet-stream';
    responseHeaders.set('Content-Type', contentType);
    const contentLength = backendRes.headers.get('content-length');
    if (contentLength) responseHeaders.set('Content-Length', contentLength);
    responseHeaders.set('Accept-Ranges', 'bytes');
    responseHeaders.set('Cache-Control', 'public, max-age=31536000, s-maxage=31536000, immutable');

    return new NextResponse(null, {
      status: backendRes.status,
      headers: responseHeaders,
    });
  } catch (err: unknown) {
    console.error('[Media Proxy HEAD Error]', err);
    return new NextResponse(null, { status: 502 });
  }
}