class State

class State implements StateInterface {
    
    /**
     * The workflow the state is attached to.
     *
     * @var \Drupal\workflows\WorkflowTypeInterface
     */
    protected $workflow;
    
    /**
     * The state's ID.
     *
     * @var string
     */
    protected $id;
    
    /**
     * The state's label.
     *
     * @var string
     */
    protected $label;
    
    /**
     * The state's weight.
     *
     * @var int
     */
    protected $weight;
    
    /**
     * State constructor.
     *
     * @param \Drupal\workflows\WorkflowTypeInterface $workflow
     *   The workflow the state is attached to.
     * @param string $id
     *   The state's ID.
     * @param string $label
     *   The state's label.
     * @param int $weight
     *   The state's weight.
     */
    public function __construct(WorkflowTypeInterface $workflow, $id, $label, $weight = 0) {
        $this->workflow = $workflow;
        $this->id = $id;
        $this->label = $label;
        $this->weight = $weight;
    }
    
    /**
     * {@inheritdoc}
     */
    public function id() {
        return $this->id;
    }
    
    /**
     * {@inheritdoc}
     */
    public function label() {
        return $this->label;
    }
    
    /**
     * {@inheritdoc}
     */
    public function weight() {
        return $this->weight;
    }
    
    /**
     * {@inheritdoc}
     */
    public function canTransitionTo($to_state_id) {
        return $this->workflow
            ->hasTransitionFromStateToState($this->id, $to_state_id);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getTransitionTo($to_state_id) {
        if (!$this->canTransitionTo($to_state_id)) {
            throw new \InvalidArgumentException("Can not transition to '{$to_state_id}' state");
        }
        return $this->workflow
            ->getTransitionFromStateToState($this->id(), $to_state_id);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getTransitions() {
        return $this->workflow
            ->getTransitionsForState($this->id);
    }
    
    /**
     * Helper method to convert a State value object to a label.
     *
     * @param \Drupal\workflows\StateInterface $state
     *   The state.
     *
     * @return string
     *   The label of the state.
     */
    public static function labelCallback(StateInterface $state) {
        return $state->label();
    }

}