import type { APIRoute } from 'astro';

// Helper function to refresh the access token
async function refreshSpotifyToken(refreshToken: string, clientId: string, clientSecret: string) {
  const response = await fetch('https://accounts.spotify.com/api/token', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded',
      'Authorization': `Basic ${btoa(`${clientId}:${clientSecret}`)}`,
    },
    body: new URLSearchParams({
      grant_type: 'refresh_token',
      refresh_token: refreshToken,
    }),
  });

  if (!response.ok) {
    throw new Error('Failed to refresh token');
  }

  return await response.json();
}

// Function to fetch current track from Spotify
async function fetchCurrentTrack() {
  try {
    const clientId = import.meta.env.SPOTIFY_CLIENT_ID;
    const clientSecret = import.meta.env.SPOTIFY_CLIENT_SECRET;
    let accessToken = import.meta.env.SPOTIFY_ACCESS_TOKEN;
    const refreshToken = import.meta.env.SPOTIFY_REFRESH_TOKEN;

    if (!clientId || !clientSecret || !refreshToken) {
      return null;
    }

    // Try to fetch current track with existing token
    let spotifyResponse = await fetch('https://api.spotify.com/v1/me/player/currently-playing', {
      headers: {
        'Authorization': `Bearer ${accessToken}`,
        'Content-Type': 'application/json',
      },
    });

    // If token is expired (401), refresh it
    if (spotifyResponse.status === 401) {
      try {
        const tokenData = await refreshSpotifyToken(refreshToken, clientId, clientSecret);
        accessToken = tokenData.access_token;
        
        // Retry the request with new token
        spotifyResponse = await fetch('https://api.spotify.com/v1/me/player/currently-playing', {
          headers: {
            'Authorization': `Bearer ${accessToken}`,
            'Content-Type': 'application/json',
          },
        });
      } catch (refreshError) {
        console.error('Failed to refresh token:', refreshError);
        return null;
      }
    }

    if (spotifyResponse.status === 204) {
      // Nothing is currently playing
      return {
        is_playing: false,
        item: null
      };
    }

    if (!spotifyResponse.ok) {
      return null;
    }

    const data = await spotifyResponse.json();
    
    return {
      is_playing: data.is_playing,
      item: data.item ? {
        name: data.item.name,
        artists: data.item.artists,
        is_playing: data.is_playing,
        external_urls: data.item.external_urls
      } : null
    };

  } catch (error) {
    console.error('Spotify API Error:', error);
    return null;
  }
}

export const GET: APIRoute = async ({ request }) => {
  // Set up Server-Sent Events
  const encoder = new TextEncoder();
  let controller: ReadableStreamDefaultController<Uint8Array>;
  let isClosed = false;
  let pollInterval: NodeJS.Timeout | null = null;
  
  const stream = new ReadableStream({
    start(ctrl) {
      controller = ctrl;
    },
    cancel() {
      // Client disconnected
      console.log('SSE stream cancelled by client');
      isClosed = true;
      if (pollInterval) {
        clearInterval(pollInterval);
        pollInterval = null;
      }
    }
  });

  // Function to send SSE message
  const sendMessage = (data: any) => {
    if (isClosed) {
      return; // Don't try to send if stream is closed
    }
    
    try {
      const message = `data: ${JSON.stringify(data)}\n\n`;
      controller.enqueue(encoder.encode(message));
    } catch (error) {
      if (error instanceof TypeError && error.message.includes('Controller is already closed')) {
        console.log('SSE controller is closed, stopping polling');
        isClosed = true;
        if (pollInterval) {
          clearInterval(pollInterval);
          pollInterval = null;
        }
      } else {
        console.error('Error sending SSE message:', error);
      }
    }
  };

  // Start polling and sending updates
  let lastTrackData: any = null;
  
  const poll = async () => {
    if (isClosed) {
      if (pollInterval) {
        clearInterval(pollInterval);
        pollInterval = null;
      }
      return;
    }

    try {
      const currentTrack = await fetchCurrentTrack();
      
      // Only send if data has changed and stream is still open
      if (!isClosed && JSON.stringify(currentTrack) !== JSON.stringify(lastTrackData)) {
        lastTrackData = currentTrack;
        sendMessage(currentTrack || { is_playing: false, item: null });
      }
    } catch (error) {
      if (!isClosed) {
        console.error('Polling error:', error);
      }
    }
  };

  // Send initial data
  poll();
  
  // Poll every 3 seconds
  pollInterval = setInterval(poll, 3000);

  // Clean up when client disconnects (abort signal)
  request.signal.addEventListener('abort', () => {
    console.log('SSE request aborted');
    isClosed = true;
    if (pollInterval) {
      clearInterval(pollInterval);
      pollInterval = null;
    }
  });

  return new Response(stream, {
    headers: {
      'Content-Type': 'text/event-stream',
      'Cache-Control': 'no-cache',
      'Connection': 'keep-alive',
      'Access-Control-Allow-Origin': '*',
      'Access-Control-Allow-Headers': 'Cache-Control',
    },
  });
};