Obtain OAuth 2.0 Access Token Using Client Credentials Grant

const fetch = require('node-fetch');

async function getClientCredentialsToken(tokenUrl, clientId, clientSecret, scope = '') {
  try {
    const authString = Buffer.from(`${clientId}:${clientSecret}`).toString('base64');
    const params = new URLSearchParams();
    params.append('grant_type', 'client_credentials');
    if (scope) {
      params.append('scope', scope);
    }

    const response = await fetch(tokenUrl, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/x-www-form-urlencoded',
        'Authorization': `Basic ${authString}`
      },
      body: params.toString()
    });

    if (!response.ok) {
      const errorText = await response.text();
      throw new Error(`Failed to get token: ${response.status} - ${errorText}`);
    }

    const data = await response.json();
    return data.access_token;
  } catch (error) {
    console.error('Error fetching client credentials token:', error);
    throw error;
  }
}

// Usage example:
// const TOKEN_URL = 'https://api.example.com/oauth/token';
// const CLIENT_ID = 'your_client_id';
// const CLIENT_SECRET = 'your_client_secret';
// const SCOPE = 'read:data write:data'; // Optional scope

// (async () => {
//   try {
//     const accessToken = await getClientCredentialsToken(TOKEN_URL, CLIENT_ID, CLIENT_SECRET, SCOPE);
//     console.log('Access Token:', accessToken);
//     // Use accessToken to make subsequent API calls
//   } catch (error) {
//     console.error('Application failed to authenticate:', error);
//   }
// })();