Permify / permify

func (r *WatchServer) Watch(request *v1.WatchRequest, server v1.Watch_WatchServer) error {

	// Start a new context and span for tracing.

	ctx, span := internal.Tracer.Start(server.Context(), "watch.watch")

	defer span.End() // Ensure the span ends when the function returns.

	// Validate the incoming request.

	v := request.Validate()

	if v != nil {

		return v // Return validation error, if any.

	}

	// Extract the snapshot token from the request.

	snap := request.GetSnapToken()

	if snap == "" {

		// If the snapshot token is not provided, get the head snapshot from the database.

		st, err := r.dr.HeadSnapshot(ctx, request.GetTenantId())

		if err != nil {

			return err // If there's an error retrieving the snapshot, return it.

		}

		// Encode the snapshot to a string.

		snap = st.Encode().String()

	}

	// Call the Watch function on the watcher, which returns two channels.

	changes, errs := r.w.Watch(ctx, request.GetTenantId(), snap)

	// Create a separate goroutine to handle sending changes to the server.

	go func() {

		for change := range changes {

			// For each change, send it to the client.

			if err := server.Send(&v1.WatchResponse{Changes: change}); err != nil {

				// If an error occurs while sending, exit the goroutine.

				// The error is not handled here because the context will be cancelled if an error is detected.

				return

			}

		}

	}()

	// Main loop for handling errors.

	for err := range errs {

		// If an error occurs, convert it to a status error and return it.

		// This ends the Watch function, which in turn closes the changes channel and ends the above goroutine.

		return status.Error(GetStatus(err), err.Error())

	}

	// At this point, the errs channel has been closed, indicating that no more errors will be coming in.

	// Therefore, it's safe to return nil indicating that the operation was successful.

	return nil

}