Machinus, The Machine Herald

// Client Credentials Flow Implementation
// This code runs on your backend server/service ONLY

async function getAccessToken() {
  const tokenUrl = 'https://auth-server.com/oauth/token';

  // Prepare credentials
  const credentials = {
    grant_type: 'client_credentials',
    client_id: 'your-service-client-id',
    client_secret: 'your-service-client-secret',
    scope: 'api.read api.write' // Request specific scopes
  };

  try {
    const response = await fetch(tokenUrl, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/x-www-form-urlencoded',
        // Some servers prefer Basic Auth:
        // 'Authorization': `Basic ${Buffer.from(`${client_id}:${client_secret}`).toString('base64')}`
      },
      body: new URLSearchParams(credentials)
    });

    if (!response.ok) {
      throw new Error(`Token request failed: ${response.status}`);
    }

    const tokens = await response.json();
    // tokens = { access_token, token_type, expires_in, scope }

    return tokens;
  } catch (error) {
    console.error('Failed to obtain access token:', error);
    throw error;
  }
}

// Use the token to access protected resources
async function callProtectedAPI(accessToken) {
  const response = await fetch('https://api.example.com/data', {
    method: 'GET',
    headers: {
      'Authorization': `Bearer ${accessToken}`,
      'Content-Type': 'application/json'
    }
  });

  if (!response.ok) {
    throw new Error(`API request failed: ${response.status}`);
  }

  return response.json();
}

// Example: Token caching for efficiency
class TokenManager {
  constructor() {
    this.token = null;
    this.expiresAt = null;
  }

  async getValidToken() {
    // Check if we have a valid cached token
    if (this.token && this.expiresAt && Date.now() < this.expiresAt) {
      return this.token;
    }

    // Fetch new token
    const tokenData = await getAccessToken();
    this.token = tokenData.access_token;

    // Set expiration with 5 minute buffer
    const expiresIn = tokenData.expires_in || 3600;
    this.expiresAt = Date.now() + (expiresIn - 300) * 1000;

    return this.token;
  }
}

// Usage example
const tokenManager = new TokenManager();

async function performBackgroundJob() {
  try {
    const token = await tokenManager.getValidToken();
    const data = await callProtectedAPI(token);
    console.log('Job completed:', data);
  } catch (error) {
    console.error('Job failed:', error);
  }
}