backend/src/utils/media/spotify.util.ts

import { secureFetch } from '../network/security.util.js';

let cachedToken: string | null = null;
let tokenExpiry = 0;

export async function getSpotifyAccessToken(): Promise<string> {
  if (cachedToken && Date.now() < tokenExpiry) {
    return cachedToken;
  }

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

  if (!clientId || !clientSecret) {
    throw new Error('Spotify credentials missing');
  }

  const authString = Buffer.from(`${clientId}:${clientSecret}`).toString(
    'base64'
  );
  const response = await secureFetch('https://accounts.spotify.com/api/token', {
    method: 'POST',
    headers: {
      Authorization: `Basic ${authString}`,
      'Content-Type': 'application/x-www-form-urlencoded',
    },
    body: 'grant_type=client_credentials',
  });

  if (!response.ok) {
    const errorText = await response.text();
    const message = `Spotify auth failed: ${response.status} - ${errorText}`;
    throw new Error(message);
  }

  const data = (await response.json()) as {
    access_token: string;
    expires_in: number;
  };
  cachedToken = data.access_token;
  tokenExpiry = Date.now() + data.expires_in * 1000 - 60000;

  return cachedToken;
}