const axios = require('axios');
const qs = require('qs');
const config = require('../config.json');

let accessToken = null;
let tokenExpires = 0;

async function getAccessToken() {
  if (accessToken && Date.now() < tokenExpires) return accessToken;

  const data = qs.stringify({
    grant_type: 'client_credentials',
    client_id: config.SpotifyClientID,
    client_secret: config.SpotifyClientSecret,
  });

  const res = await axios.post('https://accounts.spotify.com/api/token', data, {
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
  });

  accessToken = res.data.access_token;
  tokenExpires = Date.now() + res.data.expires_in * 1000;
  return accessToken;
}

async function fetchSpotifyPlaylist(playlistUrl) {
  const match = playlistUrl.match(/playlist\/([a-zA-Z0-9]+)/);
  if (!match) throw new Error('Invalid Spotify playlist URL');

  const playlistId = match[1];
  const token = await getAccessToken();
  const headers = { Authorization: `Bearer ${token}` };

  let offset = 0;
  const limit = 100;
  let allTracks = [];

  while (true) {
    const res = await axios.get(`https://api.spotify.com/v1/playlists/${playlistId}/tracks`, {
      headers,
      params: { offset, limit },
    });

    const tracks = res.data.items;
    if (!tracks.length) break;

    for (const item of tracks) {
      const track = item.track;
      if (!track || !track.name || !track.artists) continue;

      const artists = track.artists.map(a => a.name).join(', ');
      allTracks.push({
        title: track.name,
        artist: artists,
        duration: Math.floor(track.duration_ms / 1000),
        url: track.external_urls.spotify,
        thumbnail: track.album?.images?.[0]?.url || '',
      });
    }

    offset += limit;
  }

  return allTracks;
}

async function getSpotifyData(url) {
  const token = await getAccessToken();
  const headers = { Authorization: `Bearer ${token}` };

  // Track
  if (url.includes('/track/')) {
    const id = url.split('/track/')[1].split('?')[0];
    const res = await axios.get(`https://api.spotify.com/v1/tracks/${id}`, { headers });
    const t = res.data;

    return [{
      title: t.name,
      artist: t.artists.map(a => a.name).join(', '),
      duration: Math.floor(t.duration_ms / 1000),
      url,
      thumbnail: t.album?.images?.[0]?.url || '',
    }];
  }

  // Playlist
  if (url.includes('/playlist/')) {
    return await fetchSpotifyPlaylist(url);
  }

  return [];
}

module.exports = { fetchSpotifyPlaylist, getSpotifyData };