class ResponsiveImageStyle

class ResponsiveImageStyle extends ConfigEntityBase implements ResponsiveImageStyleInterface {
  
  /**
   * The responsive image ID (machine name).
   *
   * @var string
   */
  protected $id;
  
  /**
   * The responsive image label.
   *
   * @var string
   */
  protected $label;
  
  /**
   * The image style mappings.
   *
   * Each image style mapping array contains the following keys:
   *   - image_mapping_type: Either 'image_style' or 'sizes'.
   *   - image_mapping:
   *     - If image_mapping_type is 'image_style', the image style ID (a
   *       string).
   *     - If image_mapping_type is 'sizes', an array with following keys:
   *       - sizes: The value for the 'sizes' attribute.
   *       - sizes_image_styles: The image styles to use for the 'srcset'
   *         attribute.
   *   - breakpoint_id: The breakpoint ID for this image style mapping.
   *   - multiplier: The multiplier for this image style mapping.
   *
   * @var array
   */
  protected $image_style_mappings = [];
  
  /**
   * @var array
   */
  protected $keyedImageStyleMappings;
  
  /**
   * The responsive image breakpoint group.
   *
   * @var string
   */
  protected $breakpoint_group = '';
  
  /**
   * The fallback image style.
   *
   * @var string
   */
  protected $fallback_image_style = '';
  
  /**
   * {@inheritdoc}
   */
  public function __construct(array $values, $entity_type_id = 'responsive_image_style') {
    parent::__construct($values, $entity_type_id);
  }
  
  /**
   * {@inheritdoc}
   */
  public function addImageStyleMapping($breakpoint_id, $multiplier, array $image_style_mapping) {
    // If there is an existing mapping, overwrite it.
    foreach ($this->image_style_mappings as &$mapping) {
      if ($mapping['breakpoint_id'] === $breakpoint_id && $mapping['multiplier'] === $multiplier) {
        $mapping = [
          'breakpoint_id' => $breakpoint_id,
          'multiplier' => $multiplier,
        ] + $image_style_mapping;
        $this->keyedImageStyleMappings = NULL;
        return $this;
      }
    }
    $this->image_style_mappings[] = [
      'breakpoint_id' => $breakpoint_id,
      'multiplier' => $multiplier,
    ] + $image_style_mapping;
    $this->keyedImageStyleMappings = NULL;
    return $this;
  }
  
  /**
   * {@inheritdoc}
   */
  public function hasImageStyleMappings() {
    $mappings = $this->getKeyedImageStyleMappings();
    return !empty($mappings);
  }
  
  /**
   * {@inheritdoc}
   */
  public function getKeyedImageStyleMappings() {
    if (!$this->keyedImageStyleMappings) {
      $this->keyedImageStyleMappings = [];
      foreach ($this->image_style_mappings as $mapping) {
        if (!static::isEmptyImageStyleMapping($mapping)) {
          $this->keyedImageStyleMappings[$mapping['breakpoint_id']][$mapping['multiplier']] = $mapping;
        }
      }
    }
    return $this->keyedImageStyleMappings;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getImageStyleMappings() {
    return $this->image_style_mappings;
  }
  
  /**
   * {@inheritdoc}
   */
  public function setBreakpointGroup($breakpoint_group) {
    // If the breakpoint group is changed then the image style mappings are
    // invalid.
    if ($breakpoint_group !== $this->breakpoint_group) {
      $this->removeImageStyleMappings();
    }
    $this->breakpoint_group = $breakpoint_group;
    return $this;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getBreakpointGroup() {
    return $this->breakpoint_group;
  }
  
  /**
   * {@inheritdoc}
   */
  public function setFallbackImageStyle($fallback_image_style) {
    $this->fallback_image_style = $fallback_image_style;
    return $this;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getFallbackImageStyle() {
    return $this->fallback_image_style;
  }
  
  /**
   * {@inheritdoc}
   */
  public function removeImageStyleMappings() {
    $this->image_style_mappings = [];
    $this->keyedImageStyleMappings = NULL;
    return $this;
  }
  
  /**
   * {@inheritdoc}
   */
  public function calculateDependencies() {
    parent::calculateDependencies();
    $providers = \Drupal::service('breakpoint.manager')->getGroupProviders($this->breakpoint_group);
    foreach ($providers as $provider => $type) {
      $this->addDependency($type, $provider);
    }
    // Extract all the styles from the image style mappings.
    $styles = ImageStyle::loadMultiple($this->getImageStyleIds());
    array_walk($styles, function ($style) {
      $this->addDependency('config', $style->getConfigDependencyName());
    });
    return $this;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function isEmptyImageStyleMapping(array $image_style_mapping) {
    if (!empty($image_style_mapping)) {
      switch ($image_style_mapping['image_mapping_type']) {
        case 'sizes':
          // The image style mapping must have a sizes attribute defined and one
          // or more image styles selected.
          if ($image_style_mapping['image_mapping']['sizes'] && $image_style_mapping['image_mapping']['sizes_image_styles']) {
            return FALSE;
          }
          break;

        case 'image_style':
          // The image style mapping must have an image style selected.
          if ($image_style_mapping['image_mapping']) {
            return FALSE;
          }
          break;

      }
    }
    return TRUE;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getImageStyleMapping($breakpoint_id, $multiplier) {
    $map = $this->getKeyedImageStyleMappings();
    if (isset($map[$breakpoint_id][$multiplier])) {
      return $map[$breakpoint_id][$multiplier];
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function getImageStyleIds() {
    $image_styles = [
      $this->getFallbackImageStyle(),
    ];
    foreach ($this->getImageStyleMappings() as $image_style_mapping) {
      // Only image styles of non-empty mappings should be loaded.
      if (!$this::isEmptyImageStyleMapping($image_style_mapping)) {
        switch ($image_style_mapping['image_mapping_type']) {
          case 'image_style':
            $image_styles[] = $image_style_mapping['image_mapping'];
            break;

          case 'sizes':
            $image_styles = array_merge($image_styles, $image_style_mapping['image_mapping']['sizes_image_styles']);
            break;

        }
      }
    }
    return array_values(array_filter(array_unique($image_styles)));
  }

}