class WorkflowTypeBase

abstract class WorkflowTypeBase extends PluginBase implements WorkflowTypeInterface {
    use PluginWithFormsTrait;
    
    /**
     * A regex for matching a valid state/transition machine name.
     */
    const VALID_ID_REGEX = '/[^a-z0-9_]+/';
    
    /**
     * {@inheritdoc}
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->setConfiguration($configuration);
    }
    
    /**
     * {@inheritdoc}
     */
    public function label() {
        $definition = $this->getPluginDefinition();
        // The label can be an object.
        // @see \Drupal\Core\StringTranslation\TranslatableMarkup
        return $definition['label'];
    }
    
    /**
     * {@inheritdoc}
     */
    public function workflowHasData(WorkflowInterface $workflow) {
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function workflowStateHasData(WorkflowInterface $workflow, StateInterface $state) {
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getConfiguration() {
        return $this->configuration;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setConfiguration(array $configuration) {
        $this->configuration = $configuration + $this->defaultConfiguration();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getRequiredStates() {
        return $this->getPluginDefinition()['required_states'];
    }
    
    /**
     * {@inheritdoc}
     */
    public function defaultConfiguration() {
        return [
            'states' => [],
            'transitions' => [],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        return [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function onDependencyRemoval(array $dependencies) {
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getInitialState() {
        $ordered_states = $this->getStates();
        return reset($ordered_states);
    }
    
    /**
     * {@inheritdoc}
     */
    public function addState($state_id, $label) {
        if ($this->hasState($state_id)) {
            throw new \InvalidArgumentException("The state '{$state_id}' already exists in workflow.");
        }
        if (preg_match(static::VALID_ID_REGEX, $state_id)) {
            throw new \InvalidArgumentException("The state ID '{$state_id}' must contain only lowercase letters, numbers, and underscores");
        }
        $this->configuration['states'][$state_id] = [
            'label' => $label,
            'weight' => $this->getNextWeight($this->configuration['states']),
        ];
        ksort($this->configuration['states']);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasState($state_id) {
        return isset($this->configuration['states'][$state_id]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getStates($state_ids = NULL) {
        if ($state_ids === NULL) {
            $state_ids = array_keys($this->configuration['states']);
        }
        
        /** @var \Drupal\workflows\StateInterface[] $states */
        $states = array_combine($state_ids, array_map([
            $this,
            'getState',
        ], $state_ids));
        return static::labelWeightMultisort($states);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getState($state_id) {
        if (!isset($this->configuration['states'][$state_id])) {
            throw new \InvalidArgumentException("The state '{$state_id}' does not exist in workflow.");
        }
        return new State($this, $state_id, $this->configuration['states'][$state_id]['label'], $this->configuration['states'][$state_id]['weight']);
    }
    
    /**
     * {@inheritdoc}
     */
    public function setStateLabel($state_id, $label) {
        if (!$this->hasState($state_id)) {
            throw new \InvalidArgumentException("The state '{$state_id}' does not exist in workflow.");
        }
        $this->configuration['states'][$state_id]['label'] = $label;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setStateWeight($state_id, $weight) {
        if (!$this->hasState($state_id)) {
            throw new \InvalidArgumentException("The state '{$state_id}' does not exist in workflow.");
        }
        if (!is_numeric($weight)) {
            $label = $this->getState($state_id)
                ->label();
            throw new \InvalidArgumentException("The weight '{$weight}' must be numeric for state '{$label}'.");
        }
        $this->configuration['states'][$state_id]['weight'] = $weight;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function deleteState($state_id) {
        if (!$this->hasState($state_id)) {
            throw new \InvalidArgumentException("The state '{$state_id}' does not exist in workflow.");
        }
        if (count($this->configuration['states']) === 1) {
            throw new \InvalidArgumentException("The state '{$state_id}' can not be deleted from workflow as it is the only state.");
        }
        foreach ($this->configuration['transitions'] as $transition_id => $transition) {
            if ($transition['to'] === $state_id) {
                $this->deleteTransition($transition_id);
                continue;
            }
            $from_key = array_search($state_id, $transition['from'], TRUE);
            if ($from_key !== FALSE) {
                // Remove state from the from array.
                unset($transition['from'][$from_key]);
                if (empty($transition['from'])) {
                    // There are no more 'from' entries, remove the transition.
                    $this->deleteTransition($transition_id);
                    continue;
                }
                // We changed the from state, update the transition.
                $this->setTransitionFromStates($transition_id, $transition['from']);
            }
        }
        unset($this->configuration['states'][$state_id]);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function addTransition($transition_id, $label, array $from_state_ids, $to_state_id) {
        if ($this->hasTransition($transition_id)) {
            throw new \InvalidArgumentException("The transition '{$transition_id}' already exists in workflow.");
        }
        if (preg_match(static::VALID_ID_REGEX, $transition_id)) {
            throw new \InvalidArgumentException("The transition ID '{$transition_id}' must contain only lowercase letters, numbers, and underscores.");
        }
        if (!$this->hasState($to_state_id)) {
            throw new \InvalidArgumentException("The state '{$to_state_id}' does not exist in workflow.");
        }
        $this->configuration['transitions'][$transition_id] = [
            'label' => $label,
            'from' => [],
            'to' => $to_state_id,
            // Always add to the end.
'weight' => $this->getNextWeight($this->configuration['transitions']),
        ];
        try {
            $this->setTransitionFromStates($transition_id, $from_state_ids);
        } catch (\InvalidArgumentException $e) {
            unset($this->configuration['transitions'][$transition_id]);
            throw $e;
        }
        ksort($this->configuration['transitions']);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getTransitions(array $transition_ids = NULL) {
        if ($transition_ids === NULL) {
            $transition_ids = array_keys($this->configuration['transitions']);
        }
        
        /** @var \Drupal\workflows\TransitionInterface[] $transitions */
        $transitions = array_combine($transition_ids, array_map([
            $this,
            'getTransition',
        ], $transition_ids));
        return static::labelWeightMultisort($transitions);
    }
    
    /**
     * Sort states or transitions by weight, label, and key.
     *
     * @param \Drupal\workflows\StateInterface[]|\Drupal\workflows\TransitionInterface[] $objects
     *   An array of state or transition objects to multi-sort, keyed by the
     *   state or transition ID.
     *
     * @return \Drupal\workflows\StateInterface[]|\Drupal\workflows\TransitionInterface[]
     *   An array of sorted transitions or states, keyed by the state or
     *   transition ID.
     */
    protected static function labelWeightMultisort($objects) {
        if (count($objects) > 1) {
            // Separate weights, labels, and keys into arrays.
            $weights = $labels = [];
            $keys = array_keys($objects);
            foreach ($objects as $id => $object) {
                $weights[$id] = $object->weight();
                $labels[$id] = $object->label();
            }
            // Sort weights, labels, and keys in the same order as each other.
            array_multisort($weights, SORT_NUMERIC, SORT_ASC, $labels, SORT_NATURAL, SORT_ASC, $keys);
            // Combine keys and weights to make sure the weights are keyed with the
            // correct keys.
            $weights = array_combine($keys, $weights);
            // Return the objects sorted by weight.
            return array_replace($weights, $objects);
        }
        return $objects;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getTransition($transition_id) {
        if (!$this->hasTransition($transition_id)) {
            throw new \InvalidArgumentException("The transition '{$transition_id}' does not exist in workflow.");
        }
        return new Transition($this, $transition_id, $this->configuration['transitions'][$transition_id]['label'], $this->configuration['transitions'][$transition_id]['from'], $this->configuration['transitions'][$transition_id]['to'], $this->configuration['transitions'][$transition_id]['weight']);
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasTransition($transition_id) {
        return isset($this->configuration['transitions'][$transition_id]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getTransitionsForState($state_id, $direction = TransitionInterface::DIRECTION_FROM) {
        $transition_ids = array_keys(array_filter($this->configuration['transitions'], function ($transition) use ($state_id, $direction) {
            return in_array($state_id, (array) $transition[$direction], TRUE);
        }));
        return $this->getTransitions($transition_ids);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getTransitionFromStateToState($from_state_id, $to_state_id) {
        $transition_id = $this->getTransitionIdFromStateToState($from_state_id, $to_state_id);
        if (empty($transition_id)) {
            throw new \InvalidArgumentException("The transition from '{$from_state_id}' to '{$to_state_id}' does not exist in workflow.");
        }
        return $this->getTransition($transition_id);
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasTransitionFromStateToState($from_state_id, $to_state_id) {
        return $this->getTransitionIdFromStateToState($from_state_id, $to_state_id) !== NULL;
    }
    
    /**
     * Gets the transition ID from state to state.
     *
     * @param string $from_state_id
     *   The state ID to transition from.
     * @param string $to_state_id
     *   The state ID to transition to.
     *
     * @return string|null
     *   The transition ID, or NULL if no transition exists.
     */
    protected function getTransitionIdFromStateToState($from_state_id, $to_state_id) {
        foreach ($this->configuration['transitions'] as $transition_id => $transition) {
            if (in_array($from_state_id, $transition['from'], TRUE) && $transition['to'] === $to_state_id) {
                return $transition_id;
            }
        }
        return NULL;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setTransitionLabel($transition_id, $label) {
        if (!$this->hasTransition($transition_id)) {
            throw new \InvalidArgumentException("The transition '{$transition_id}' does not exist in workflow.");
        }
        $this->configuration['transitions'][$transition_id]['label'] = $label;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setTransitionWeight($transition_id, $weight) {
        if (!$this->hasTransition($transition_id)) {
            throw new \InvalidArgumentException("The transition '{$transition_id}' does not exist in workflow.");
        }
        if (!is_numeric($weight)) {
            $label = $this->getTransition($transition_id)
                ->label();
            throw new \InvalidArgumentException("The weight '{$weight}' must be numeric for transition '{$label}'.");
        }
        $this->configuration['transitions'][$transition_id]['weight'] = $weight;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setTransitionFromStates($transition_id, array $from_state_ids) {
        if (!$this->hasTransition($transition_id)) {
            throw new \InvalidArgumentException("The transition '{$transition_id}' does not exist in workflow.");
        }
        // Ensure that the states exist.
        foreach ($from_state_ids as $from_state_id) {
            if (!$this->hasState($from_state_id)) {
                throw new \InvalidArgumentException("The state '{$from_state_id}' does not exist in workflow.");
            }
            if ($this->hasTransitionFromStateToState($from_state_id, $this->configuration['transitions'][$transition_id]['to'])) {
                $existing_transition_id = $this->getTransitionIdFromStateToState($from_state_id, $this->configuration['transitions'][$transition_id]['to']);
                if ($transition_id !== $existing_transition_id) {
                    throw new \InvalidArgumentException("The '{$existing_transition_id}' transition already allows '{$from_state_id}' to '{$this->configuration['transitions'][$transition_id]['to']}' transitions in workflow.");
                }
            }
        }
        // Preserve the order of the state IDs in the from value and don't save any
        // keys.
        $from_state_ids = array_values($from_state_ids);
        sort($from_state_ids);
        $this->configuration['transitions'][$transition_id]['from'] = $from_state_ids;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function deleteTransition($transition_id) {
        if (!$this->hasTransition($transition_id)) {
            throw new \InvalidArgumentException("The transition '{$transition_id}' does not exist in workflow.");
        }
        unset($this->configuration['transitions'][$transition_id]);
        return $this;
    }
    
    /**
     * Gets the weight for a new state or transition.
     *
     * @param array $items
     *   An array of states or transitions information where each item has a
     *   'weight' key with a numeric value.
     *
     * @return int
     *   The weight for a new item in the array so that it has the highest weight.
     */
    protected function getNextWeight(array $items) {
        return array_reduce($items, function ($carry, $item) {
            return max($carry, $item['weight'] + 1);
        }, 0);
    }

}