server.js

const express = require('express');
const fetch = require('node-fetch');
const querystring = require('querystring');
const app = express();
const port = 7860;

const clientId = process.env.SPOTIFY_CLIENT_ID;
const clientSecret = process.env.SPOTIFY_CLIENT_SECRET;
const redirectUri = process.env.SPOTIFY_REDIRECT_URI;

app.use(express.static('public'));
app.use(express.json());

app.get('/login', (req, res) => {
  const scope = 'streaming user-read-private user-read-email user-read-currently-playing user-modify-playback-state playlist-read-private user-library-read user-library-modify user-follow-read';
  res.redirect('https://accounts.spotify.com/authorize?' +
    querystring.stringify({
      response_type: 'code',
      client_id: clientId,
      scope: scope,
      redirect_uri: redirectUri,
    }));
});

app.get('/callback', async (req, res) => {
  const code = req.query.code || null;
  const authOptions = {
    method: 'POST',
    headers: {
      'Authorization': 'Basic ' + (Buffer.from(clientId + ':' + clientSecret).toString('base64')),
      'Content-Type': 'application/x-www-form-urlencoded'
    },
    body: querystring.stringify({
      code: code,
      redirect_uri: redirectUri,
      grant_type: 'authorization_code'
    })
  };

  try {
    const response = await fetch('https://accounts.spotify.com/api/token', authOptions);
    const data = await response.json();

    if (!response.ok) {
        console.error("Error from Spotify:", data);
        res.status(response.status).send(`Error from Spotify: ${data.error_description || data.error}`);
        return;
    }

    const token = data.access_token;
    res.redirect('/#' + querystring.stringify({ access_token: token }));
    return;

  } catch (error) {
    console.error("Network or other error during token exchange:", error);
    res.status(500).send("An internal server error occurred.");
    return;
  }
});

// Endpoint to get recommendations
app.post('/recommendations', async (req, res) => {
  const { access_token, seed_tracks, seed_artists, seed_genres } = req.body;
  
  try {
    const params = new URLSearchParams();
    if (seed_tracks) params.append('seed_tracks', seed_tracks);
    if (seed_artists) params.append('seed_artists', seed_artists);
    if (seed_genres) params.append('seed_genres', seed_genres);
    params.append('limit', '20');

    const response = await fetch(`https://api.spotify.com/v1/recommendations?${params}`, {
      headers: {
        'Authorization': `Bearer ${access_token}`
      }
    });

    if (!response.ok) {
      const errorText = await response.text();
      console.error('Spotify API error:', response.status, errorText);
      res.status(response.status).json({ error: 'Failed to get recommendations' });
      return;
    }

    const data = await response.json();
    res.json(data);
  } catch (error) {
    console.error('Error getting recommendations:', error);
    res.status(500).json({ error: 'Failed to get recommendations' });
  }
});

app.listen(port, () => {
  console.log(`App listening at port ${port}`);
});