interface StateInterface

interface StateInterface {
    
    /**
     * The key of the state plugin form.
     */
    const PLUGIN_FORM_KEY = 'state';
    
    /**
     * Gets the state's ID.
     *
     * @return string
     *   The state's ID.
     */
    public function id();
    
    /**
     * Gets the state's label.
     *
     * @return string
     *   The state's label.
     */
    public function label();
    
    /**
     * Gets the state's weight.
     *
     * @return int
     *   The state's weight.
     */
    public function weight();
    
    /**
     * Determines if the state can transition to the provided state ID.
     *
     * @param $to_state_id
     *   The state to transition to.
     *
     * @return bool
     *   TRUE if the state can transition to the provided state ID. FALSE, if not.
     */
    public function canTransitionTo($to_state_id);
    
    /**
     * Gets the Transition object for the provided state ID.
     *
     * @param $to_state_id
     *   The state to transition to.
     *
     * @return \Drupal\workflows\TransitionInterface
     *   The Transition object for the provided state ID.
     *
     * @throws \InvalidArgumentException()
     *   Exception thrown when the provided state ID can not be transitioned to.
     */
    public function getTransitionTo($to_state_id);
    
    /**
     * Gets all the possible transition objects for the state.
     *
     * @return \Drupal\workflows\TransitionInterface[]
     *   All the possible transition objects for the state.
     */
    public function getTransitions();

}