# Presenter Service Interface

Exception PresenterException(message: string);

/**
 * Executes some presenting function on the server. The term "presenting" means
 * a non writing (or modifying) idempotent request. There may be some
 * side-effect allowed (like tracking calls to one presenter), but the main
 * purpose is to get data of the server, which is not autoupdate-, projector-, or
 * icc-data.
 *
 * Some purposes may be:
 * - aggregating of login data
 * - managing of whoami, if additional data is needed, that the auth service
 *   doesn't provide
 * - To get history points
 * - To get history data
 * - To get the installed version
 * - To query statistics
 * - To calculate recursive trees (e.g. origins of motions; not possible with
 *   the autoupdate service)
 * - to synchronize the servertime for countdowns
 *
 * @throws PresenterException This exception might be thrown, if there was an
 * server error (Http-500-equivalent). For user error (e.g. wrong data) use the
 * PresenterError interface.
 */
handle_request(payload: Presenter[], user_id: Id): PresenterResult[]

/**
 * This interface specifies what presenter is used with the payload for the call.
 */
Interface Presenter {
    presenter: string;
    data: any;
}

/**
 * A presenter may return anything. This is presenter-specific. But if there was
 * an error (user error, not a PresenterException), the response for this
 * presenter should follow `PresenterError`.
 *
 * TODO: Maybe we do not want to response an error but always throw an exception
 * instead.
 */
type PresenterResult = any | PresenterError;

/**
 * A common format for errors.
 */
Interface PresenterError {
    error: object;
}