class Transition

class Transition implements TransitionInterface {
    
    /**
     * The workflow that this transition is attached to.
     *
     * @var \Drupal\workflows\WorkflowTypeInterface
     */
    protected $workflow;
    
    /**
     * The transition's ID.
     *
     * @var string
     */
    protected $id;
    
    /**
     * The transition's label.
     *
     * @var string
     */
    protected $label;
    
    /**
     * The transition's from state IDs.
     *
     * @var string[]
     */
    protected $fromStateIds;
    
    /**
     * The transition's to state ID.
     *
     * @var string
     */
    protected $toStateId;
    
    /**
     * The transition's weight.
     *
     * @var int
     */
    protected $weight;
    
    /**
     * Transition constructor.
     *
     * @param \Drupal\workflows\WorkflowTypeInterface $workflow
     *   The workflow the state is attached to.
     * @param string $id
     *   The transition's ID.
     * @param string $label
     *   The transition's label.
     * @param array $from_state_ids
     *   A list of from state IDs.
     * @param string $to_state_id
     *   The to state ID.
     * @param int $weight
     *   (optional) The transition's weight. Defaults to 0.
     */
    public function __construct(WorkflowTypeInterface $workflow, $id, $label, array $from_state_ids, $to_state_id, $weight = 0) {
        $this->workflow = $workflow;
        $this->id = $id;
        $this->label = $label;
        $this->fromStateIds = $from_state_ids;
        $this->toStateId = $to_state_id;
        $this->weight = $weight;
    }
    
    /**
     * {@inheritdoc}
     */
    public function id() {
        return $this->id;
    }
    
    /**
     * {@inheritdoc}
     */
    public function label() {
        return $this->label;
    }
    
    /**
     * {@inheritdoc}
     */
    public function from() {
        return $this->workflow
            ->getStates($this->fromStateIds);
    }
    
    /**
     * {@inheritdoc}
     */
    public function to() {
        return $this->workflow
            ->getState($this->toStateId);
    }
    
    /**
     * {@inheritdoc}
     */
    public function weight() {
        return $this->weight;
    }

}