Retrieving a single entitlement

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

    // This is what we're trying to find.
    let entitlement = null;

    try {
        // GET UTF-8 JSON to the Bango Resale API and parse the JSON response
        let response = rest_client_call({
            method: "GET",
            url: base_url + "entitlement/" + entitlement_id,
            headers: {
                "Authorization": get_authorization_header(),
            },
        }).from_json();

        // The responseCode tells us the result.
        switch (response.responseCode) {
            // Success
            case "OK":
                entitlement = response;
                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_FOUND": // Invalid entitlement ID
            case "TOO_MANY_REQUESTS": // Request limit reached: try again later
                throw "Unable to retrieve 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 retrieved.
    // If retrieved, will have an entitlementId, status, and other properties:
    // see API reference.
    return entitlement;
}