Updating an entitlement

function update_entitlement (entitlement_id, properties_to_update = {}) {
    // *Always* use this endpoint prefix for the Bango Resale API.
    const base_url = "https://resale.api.bango.net";

    // This is what's returned with HTTP 2xx.
    let entitlement = null;

    // The entitlement ID is passed in the body not the path.
    // Here, assume properties_to_update is a map of entitlement
    // property names to values.
    // See API ref for details of which properties you can update.
    const request_body_params = properties_to_update
        .copy()
        .set('entitlementId', entitlement_id);

    try {
        // PATCH UTF-8 JSON to the Bango Resale API and parse the JSON response
        let response = rest_client_call({
            method: "PATCH",
            url: base_url + "entitlement",
            headers: {
                "Authorization": get_authorization_header(),
                "Content-Type": "application/json",
            },
            body: make_json_string(request_body_params),
        }).from_json();

        // The responseCode tells us the result.
        switch (response.responseCode) {
            // Success: no action required
            case "OK":
                entitlement = response;
                break;

            // More to do: The reseller must take action
            case "CLIENT_ACTION_REQUIRED":
                // This response parameter tells us what we need to do.
                switch (response.parameters.action) {
                    case "NAVIGATE_TO_URL":
                        // Send the user to a particular web page
                        // to complete a merchant-defined process.
                        // Set entitlement's notificationUrl to
                        // receive notification of entitlement
                        // changes asynchronously.
                        redirect_device_to({
                            url: response.parameters.url,
                        });
                        // Updated entitlement is returned in this case
                        // but with status PENDING.
                        entitlement = response;
                        break;

                    default:
                        // Unrecognized action.
                        // Check the documentation again.
                        throw "Unrecognized client action";
                }

                break;

            // Failures
            // These may indicate issues in your code, not the Bango Platform.
            case "BAD_REQUEST": // Invalid request
            case "UNAUTHORIZED": // Check your credentials
            case "NOT_AVAILABLE": // Unable to update this entitlement
            case "NOT_FOUND": // Invalid entitlement ID
            case "TOO_MANY_REQUESTS": // Request limit reached: try again later
                throw "Unable to update entitlement";

            // Bango Platform issues
            // These likely indicate transient problems.
            // In production code, you might want to try the request again
            // after a delay, ultimately falling back to an error state.
            case "INTERNAL_ERROR":
            case "SERVICE_UNAVAILABLE":
                throw "Bango Platform unavailable";

            // This might indicate Bango has added a new response code.
            // Check the documentation again.
            default:
                throw "Unrecognized response code";
        }

    } catch (exception) {
        // Production code might want to notify the reseller in some way,
        // and/or log full details of the exception for later analysis,
        // and degrade gracefully for the user.
        output("An error occurred!");
        output(exception);
    }

    // null if entitlement not updated.
    // if updated, will have an entitlementId, status, and other properties:
    // see API reference.
    return entitlement;
}