azure-forwarder.ts

import { ZuploContext, ZuploRequest, ZoneCache, environment } from "@zuplo/runtime";

// Get environment variables
// AZURE_AD_TENENT_ID: The tenant ID of your Azure AD (UUID)
// AZURE_AD_CLIENT_ID: The client ID of the "zuplo" Azure AD application (UUID)
// AZURE_AD_CLIENT_SECRET: The secret for the "zuplo" Azure AD application
// API_HOST: The url of your Azure App service i.e. https://zup-demo1.azurewebsites.net/
const { AZURE_AD_TENENT_ID, AZURE_AD_CLIENT_ID, AZURE_AD_CLIENT_SECRET, API_HOST } = environment;
const TOKEN_CACHE_KEY = "ad-token"

// The the token cache for slightly less than the token expiration
const TOKEN_CACHE_TTL = 60 * 55

export default async function (request: ZuploRequest, context: ZuploContext) {
  const cache = new ZoneCache("tokens", context);
  let accessToken = await cache.get(TOKEN_CACHE_KEY);
  if (!accessToken) {
    accessToken = await getAccessToken();
    // cache for 55 minutes
    cache.put(TOKEN_CACHE_KEY, accessToken, TOKEN_CACHE_TTL)
  }

  // Create new Headers and add Authorization 
  const headers = new Headers(request.headers);
  headers.set("Authorization", `Bearer ${accessToken}`);

  const url = new URL(request.url);

  // Forward request to Azure App 
  return fetch(`${API_HOST}${url.pathname}${url.search}`, {
    headers,
    body: request.body,
    method: request.method
  });
}

async function getAccessToken() {
  const body = new URLSearchParams({
    client_id: AZURE_AD_CLIENT_ID,
    scope: `${AZURE_AD_CLIENT_ID}/.default`,
    client_secret: AZURE_AD_CLIENT_SECRET,
    grant_type: "client_credentials"
  });

  const response = await fetch(`https://login.microsoftonline.com/${AZURE_AD_TENENT_ID}/oauth2/v2.0/token`, {
    headers: {
      "content-type": "application/x-www-form-urlencoded"
    },
    method: "POST",
    body
  });
  const result = await response.json();

  return result.access_token;
}