Delphi Google Cloud SDK — FCM, Pub/Sub, Calendar & more

Google Cloud Platform exposes hundreds of REST APIs — messaging, storage, queueing, identity, mapping, machine learning, productivity (Calendar, Drive, Gmail, Docs), advertising, analytics, billing and more. Until now, calling them from Delphi meant hand-writing JWT signers, OAuth2 token refreshers, multipart uploaders and SSE parsers. sgcWebSockets ships first-class components for the most common surfaces — TsgcHTTP_API_GoogleFCM for Firebase Cloud Messaging HTTP v1, TsgcHTTP_API_GoogleCloudPubSub for Cloud Pub/Sub, TsgcHTTP_API_GoogleCalendar for the Calendar API v3 — plus reusable OAuth2 + service-account-JWT infrastructure that drives every other Google endpoint and the sgcOpenAPI code generator for the long tail.

Authentication is uniform: a Google Cloud project, a service account JSON key (or an OAuth2 client for end-user flows), and the appropriate https://www.googleapis.com/auth/... scopes. The library’s JWT signer builds the assertion, requests an access token from oauth2.googleapis.com/token, and caches / refreshes it transparently. The same code runs unmodified on Windows, macOS, Linux, iOS and Android, with both VCL and FMX UI layers.

Most Google Cloud APIs accept two forms of credential: a service-account JSON key (RS256-signed JWT exchanged at oauth2.googleapis.com/token for a short-lived bearer token, no user interaction) and an OAuth2 client with the standard authorisation-code or device-code flow for end-user data (Calendar, Drive, Gmail). sgcWebSockets covers both: TsgcJWTClient signs the assertion, TsgcOAuth2Client drives the user flow, and the per-service components consume whichever credential you wire in. Tokens are cached in memory and refreshed before expiry so your application code never touches a 401.

Cloud Pub/Sub is Google’s globally distributed, at-least-once messaging fabric — the backbone of countless event-driven architectures. The same service account credential drives both ends; publishers POST messages to a topic, subscribers either pull on a schedule or accept push deliveries on an HTTPS endpoint.

uses
  sgcHTTP_API_GoogleCloudPubSub;

var
  vPubSub: TsgcHTTP_API_GoogleCloudPubSub;
begin
  vPubSub := TsgcHTTP_API_GoogleCloudPubSub.Create(nil);
  try
    vPubSub.ProjectId          := 'my-project';
    vPubSub.ServiceAccountFile := 'C:\keys\my-project-pubsub.json';

    // Publish
    vPubSub.Publish('orders', '{"orderId":1234,"total":42.50}');

    // Pull
    vPubSub.OnMessageReceived := DoMessageReceived;
    vPubSub.Subscribe('orders-worker');  // long-running pull loop
  finally
    vPubSub.Free;
  end;
end;