export const OPTIONS = async () => {
  return new Response(null, {
    status: 204,
    headers: {
      'Access-Control-Allow-Origin': '*',
      'Access-Control-Allow-Methods': 'GET, OPTIONS',
      'Access-Control-Allow-Headers': 'Content-Type, Range',
      'Access-Control-Max-Age': '86400',
    },
  });
};

export const GET = async ({ request, url }) => {
  const targetUrl = url.searchParams.get('url');
  
  if (!targetUrl) {
    return new Response(JSON.stringify({ error: 'Missing target URL' }), {
      status: 400,
      headers: { 'Content-Type': 'application/json' }
    });
  }

  try {
    const headers = new Headers();
    // Use the origin of the target URL as the referer to bypass simple checks
    const targetOrigin = new URL(targetUrl).origin;
    headers.set('Referer', targetOrigin + '/');
    headers.set('Origin', targetOrigin);
    headers.set('User-Agent', 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36');

    // Forward Range header for smooth scrubbing/seeking (HTTP 206 Partial Content support)
    const rangeHeader = request.headers.get('Range') || request.headers.get('range');
    if (rangeHeader) {
      headers.set('Range', rangeHeader);
    }

    const response = await fetch(targetUrl, { headers });

    if (!response.ok) {
      // If it's an image and it's not found, return a transparent 1x1 pixel 
      // This prevents the player from retrying and avoids broken image icons in the UI
      const isImage = targetUrl.match(/\.(jpg|jpeg|png|gif|webp|svg)(\?.*)?$/i) || 
                     targetUrl.toLowerCase().includes('preview.jpg') || 
                     targetUrl.toLowerCase().includes('thumb.jpg');

      if (isImage && response.status === 404) {
        // 1x1 transparent GIF
        const transparentPixel = Buffer.from('R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7', 'base64');
        return new Response(transparentPixel, {
          status: 200,
          headers: {
            'Content-Type': 'image/gif',
            'Access-Control-Allow-Origin': '*',
            'Cache-Control': 'public, max-age=86400'
          }
        });
      }

      console.warn(`[Proxy] Failed to fetch ${targetUrl}: ${response.status} ${response.statusText}`);
      return new Response(null, { status: response.status });
    }

    const contentType = response.headers.get('Content-Type') || '';
    
    // If it's a playlist (m3u8), we might need to rewrite relative paths to absolute ones
    // so that the player doesn't try to load them relative to the proxy URL.
    if (contentType.includes('mpegurl') || contentType.includes('x-mpegURL') || targetUrl.endsWith('.m3u8')) {
      let text = await response.text();
      const urlObj = new URL(targetUrl);
      const baseUrl = targetUrl.substring(0, targetUrl.lastIndexOf('/') + 1);

      // Rewrite relative paths to absolute URLs pointing back to the proxy
      // This ensures that all segments also go through the proxy to bypass CORS
      const proxiedText = text.split('\n').map(line => {
        const trimmed = line.trim();
        if (!trimmed) return line;

        // If it is a tag/comment line
        if (trimmed.startsWith('#')) {
          // Check for URI attribute in EXT tags (like EXT-X-KEY, EXT-X-MAP, EXT-X-MEDIA)
          if (trimmed.includes('URI=')) {
            return trimmed.replace(/URI=(["'])([^"'\r\n]+)\1/g, (match, quote, p1) => {
              let absolutePath = p1;
              if (!p1.startsWith('http')) {
                absolutePath = p1.startsWith('/') 
                  ? urlObj.origin + p1 
                  : baseUrl + p1;
              }
              return `URI=${quote}/api/proxy-media?url=${encodeURIComponent(absolutePath)}${quote}`;
            });
          }
          return line;
        }

        // If it is a segment URL (non-tag line)
        // If it's already an absolute URL, wrap it in proxy
        if (trimmed.startsWith('http')) {
          return `/api/proxy-media?url=${encodeURIComponent(trimmed)}`;
        }
        // If it's a relative path, make it absolute and wrap it
        const absolutePath = trimmed.startsWith('/') 
          ? urlObj.origin + trimmed 
          : baseUrl + trimmed;
        return `/api/proxy-media?url=${encodeURIComponent(absolutePath)}`;
      }).join('\n');

      return new Response(proxiedText, {
        status: 200,
        headers: {
          'Content-Type': 'application/x-mpegURL',
          'Access-Control-Allow-Origin': '*',
          'Cache-Control': 'no-cache'
        }
      });
    }

    // For other media (images, segments), stream the response directly to the browser
    // This achieves zero-latency start and supports seeking (206 Partial Content)
    const status = response.status;
    const responseHeaders = new Headers({
      'Content-Type': contentType,
      'Access-Control-Allow-Origin': '*',
      'Cache-Control': 'public, max-age=3600'
    });

    // Copy Range-related headers from destination response if they exist
    const contentRange = response.headers.get('Content-Range') || response.headers.get('content-range');
    if (contentRange) {
      responseHeaders.set('Content-Range', contentRange);
    }
    const contentLength = response.headers.get('Content-Length') || response.headers.get('content-length');
    if (contentLength) {
      responseHeaders.set('Content-Length', contentLength);
    }
    const acceptRanges = response.headers.get('Accept-Ranges') || response.headers.get('accept-ranges');
    if (acceptRanges) {
      responseHeaders.set('Accept-Ranges', acceptRanges);
    }

    return new Response(response.body, {
      status: status,
      headers: responseHeaders
    });
  } catch (error) {
    console.error(`[Proxy] Error:`, error);
    return new Response(null, { status: 500 });
  }
};