<?php

namespace Drupal\Core\Plugin;

use Drupal\Component\Plugin\ConfigurableInterface;
use Drupal\Component\Plugin\Context\ContextInterface as ComponentContextInterface;
use Drupal\Component\Plugin\Definition\ContextAwarePluginDefinitionInterface;
use Drupal\Component\Plugin\Exception\ContextException;
use Drupal\Core\Cache\Cache;
use Drupal\Core\Cache\CacheableDependencyInterface;
use Drupal\Core\Plugin\Context\Context;
use Drupal\Core\Plugin\Context\ContextInterface;
use Symfony\Component\Validator\ConstraintViolationList;

/**
 * Provides a trait to add context-aware functionality to plugins.
 *
 * @see \Drupal\Core\Plugin\ContextAwarePluginInterface
 *
 * @ingroup plugin_api
 */
trait ContextAwarePluginTrait {

  /**
   * The data objects representing the context of this plugin.
   *
   * @var \Drupal\Core\Plugin\Context\ContextInterface[]
   */
  protected $context = [];

  /**
   * {@inheritdoc}
   */
  public function getContexts() {
    // Make sure all context objects are initialized.
    foreach ($this->getContextDefinitions() as $name => $definition) {
      $this->getContext($name);
    }
    return $this->context;
  }

  /**
   * {@inheritdoc}
   *
   * @return \Drupal\Core\Plugin\Context\ContextInterface
   *   The context object.
   */
  public function getContext($name) {
    // Check for a valid context value.
    if (!isset($this->context[$name])) {
      $this->context[$name] = new Context($this->getContextDefinition($name));
    }
    return $this->context[$name];
  }

  /**
   * {@inheritdoc}
   */
  public function setContext($name, ComponentContextInterface $context) {
    // Check that the context passed is an instance of our extended interface.
    if (!$context instanceof ContextInterface) {
      throw new ContextException("Passed $name context must be an instance of \\Drupal\\Core\\Plugin\\Context\\ContextInterface");
    }
    $this->context[$name] = $context;
  }

  /**
   * {@inheritdoc}
   */
  public function getContextValues() {
    $values = [];
    foreach ($this->getContextDefinitions() as $name => $definition) {
      $values[$name] = isset($this->context[$name]) ? $this->context[$name]->getContextValue() : NULL;
    }
    return $values;
  }

  /**
   * {@inheritdoc}
   */
  public function getContextValue($name) {
    return $this->getContext($name)->getContextValue();
  }

  /**
   * {@inheritdoc}
   */
  public function setContextValue($name, $value) {
    $this->setContext($name, Context::createFromContext($this->getContext($name), $value));
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  public function getContextMapping() {
    $configuration = $this instanceof ConfigurableInterface ? $this->getConfiguration() : $this->configuration;
    return $configuration['context_mapping'] ?? [];
  }

  /**
   * {@inheritdoc}
   */
  public function setContextMapping(array $context_mapping) {
    if ($this instanceof ConfigurableInterface) {
      $configuration = $this->getConfiguration();
      $configuration['context_mapping'] = array_filter($context_mapping);
      $this->setConfiguration($configuration);
    }
    else {
      $this->configuration['context_mapping'] = $context_mapping;
    }
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  abstract public function getPluginDefinition();

  /**
   * {@inheritdoc}
   *
   * @return \Drupal\Core\Plugin\Context\ContextDefinitionInterface[]
   *   The array of context definitions, keyed by context name.
   */
  public function getContextDefinitions() {
    $definition = $this->getPluginDefinition();
    if ($definition instanceof ContextAwarePluginDefinitionInterface) {
      return $definition->getContextDefinitions();
    }

    return !empty($definition['context_definitions']) ? $definition['context_definitions'] : [];
  }

  /**
   * {@inheritdoc}
   *
   * @return \Drupal\Core\Plugin\Context\ContextDefinitionInterface
   *   The definition against which the context value must validate.
   */
  public function getContextDefinition($name) {
    $definition = $this->getPluginDefinition();
    if ($definition instanceof ContextAwarePluginDefinitionInterface) {
      if ($definition->hasContextDefinition($name)) {
        return $definition->getContextDefinition($name);
      }
    }
    elseif (!empty($definition['context_definitions'][$name])) {
      return $definition['context_definitions'][$name];
    }
    throw new ContextException(sprintf("The %s context is not a valid context.", $name));
  }

  /**
   * {@inheritdoc}
   */
  public function validateContexts() {
    $violations = new ConstraintViolationList();

    // @todo Implement the Symfony Validator component to let the validator
    //   traverse and set property paths accordingly.
    //   See https://www.drupal.org/project/drupal/issues/3153847.
    foreach ($this->getContexts() as $context) {
      $violations->addAll($context->validate());
    }
    return $violations;
  }

  /**
   * {@inheritdoc}
   */
  public function getCacheContexts() {
    $cache_contexts = [];
    // Applied contexts can affect the cache contexts when this plugin is
    // involved in caching, collect and return them.
    foreach ($this->getContexts() as $context) {
      /** @var \Drupal\Core\Cache\CacheableDependencyInterface $context */
      if ($context instanceof CacheableDependencyInterface) {
        $cache_contexts = Cache::mergeContexts($cache_contexts, $context->getCacheContexts());
      }
    }
    return $cache_contexts;
  }

  /**
   * {@inheritdoc}
   */
  public function getCacheTags() {
    $tags = [];
    // Applied contexts can affect the cache tags when this plugin is
    // involved in caching, collect and return them.
    foreach ($this->getContexts() as $context) {
      /** @var \Drupal\Core\Cache\CacheableDependencyInterface $context */
      if ($context instanceof CacheableDependencyInterface) {
        $tags = Cache::mergeTags($tags, $context->getCacheTags());
      }
    }
    return $tags;
  }

  /**
   * {@inheritdoc}
   */
  public function getCacheMaxAge() {
    $max_age = Cache::PERMANENT;

    // Applied contexts can affect the cache max age when this plugin is
    // involved in caching, collect and return them.
    foreach ($this->getContexts() as $context) {
      /** @var \Drupal\Core\Cache\CacheableDependencyInterface $context */
      if ($context instanceof CacheableDependencyInterface) {
        $max_age = Cache::mergeMaxAges($max_age, $context->getCacheMaxAge());
      }
    }
    return $max_age;
  }

}