class Attribute

class Attribute implements \ArrayAccess, \IteratorAggregate, MarkupInterface {
    
    /**
     * Stores the attribute data.
     *
     * @var \Drupal\Core\Template\AttributeValueBase[]
     */
    protected $storage = [];
    
    /**
     * Constructs a \Drupal\Core\Template\Attribute object.
     *
     * @param array $attributes
     *   An associative array of key-value pairs to be converted to attributes.
     */
    public function __construct($attributes = []) {
        foreach ($attributes as $name => $value) {
            $this->offsetSet($name, $value);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function offsetGet($name) {
        if (isset($this->storage[$name])) {
            return $this->storage[$name];
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function offsetSet($name, $value) {
        $this->storage[$name] = $this->createAttributeValue($name, $value);
    }
    
    /**
     * Creates the different types of attribute values.
     *
     * @param string $name
     *   The attribute name.
     * @param mixed $value
     *   The attribute value.
     *
     * @return \Drupal\Core\Template\AttributeValueBase
     *   An AttributeValueBase representation of the attribute's value.
     */
    protected function createAttributeValue($name, $value) {
        // If the value is already an AttributeValueBase object,
        // return a new instance of the same class, but with the new name.
        if ($value instanceof AttributeValueBase) {
            $class = get_class($value);
            return new $class($name, $value->value());
        }
        // An array value or 'class' attribute name are forced to always be an
        // AttributeArray value for consistency.
        if ($name == 'class' && !is_array($value)) {
            // Cast the value to string in case it implements MarkupInterface.
            $value = [
                (string) $value,
            ];
        }
        if (is_array($value)) {
            // Cast the value to an array if the value was passed in as a string.
            // @todo Decide to fix all the broken instances of class as a string
            // in core or cast them.
            $value = new AttributeArray($name, $value);
        }
        elseif (is_bool($value)) {
            $value = new AttributeBoolean($name, $value);
        }
        elseif ($value instanceof MarkupInterface) {
            // Attributes are not supposed to display HTML markup, so we just convert
            // the value to plain text.
            $value = PlainTextOutput::renderFromHtml($value);
            $value = new AttributeString($name, $value);
        }
        elseif (!is_object($value)) {
            $value = new AttributeString($name, $value);
        }
        return $value;
    }
    
    /**
     * {@inheritdoc}
     */
    public function offsetUnset($name) {
        unset($this->storage[$name]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function offsetExists($name) {
        return isset($this->storage[$name]);
    }
    
    /**
     * Adds classes or merges them on to array of existing CSS classes.
     *
     * @param string|array ...
     *   CSS classes to add to the class attribute array.
     *
     * @return $this
     */
    public function addClass() {
        $args = func_get_args();
        if ($args) {
            $classes = [];
            foreach ($args as $arg) {
                // Merge the values passed in from the classes array.
                // The argument is cast to an array to support comma separated single
                // values or one or more array arguments.
                $classes[] = (array) $arg;
            }
            $classes = array_merge(...$classes);
            // Merge if there are values, just add them otherwise.
            if (isset($this->storage['class']) && $this->storage['class'] instanceof AttributeArray) {
                // Merge the values passed in from the class value array.
                $classes = array_merge($this->storage['class']
                    ->value(), $classes);
                $this->storage['class']
                    ->exchangeArray($classes);
            }
            else {
                $this->offsetSet('class', $classes);
            }
        }
        return $this;
    }
    
    /**
     * Sets values for an attribute key.
     *
     * @param string $attribute
     *   Name of the attribute.
     * @param string|array $value
     *   Value(s) to set for the given attribute key.
     *
     * @return $this
     */
    public function setAttribute($attribute, $value) {
        $this->offsetSet($attribute, $value);
        return $this;
    }
    
    /**
     * Checks if the storage has an attribute with the given name.
     *
     * @param string $name
     *   The name of the attribute to check for.
     *
     * @return bool
     *   Returns TRUE if the attribute exists, or FALSE otherwise.
     */
    public function hasAttribute($name) {
        return array_key_exists($name, $this->storage);
    }
    
    /**
     * Removes an attribute from an Attribute object.
     *
     * @param string|array ...
     *   Attributes to remove from the attribute array.
     *
     * @return $this
     */
    public function removeAttribute() {
        $args = func_get_args();
        foreach ($args as $arg) {
            // Support arrays or multiple arguments.
            if (is_array($arg)) {
                foreach ($arg as $value) {
                    unset($this->storage[$value]);
                }
            }
            else {
                unset($this->storage[$arg]);
            }
        }
        return $this;
    }
    
    /**
     * Removes argument values from array of existing CSS classes.
     *
     * @param string|array ...
     *   CSS classes to remove from the class attribute array.
     *
     * @return $this
     */
    public function removeClass() {
        // With no class attribute, there is no need to remove.
        if (isset($this->storage['class']) && $this->storage['class'] instanceof AttributeArray) {
            $args = func_get_args();
            $classes = [];
            foreach ($args as $arg) {
                // Merge the values passed in from the classes array.
                // The argument is cast to an array to support comma separated single
                // values or one or more array arguments.
                $classes[] = (array) $arg;
            }
            $classes = array_merge(...$classes);
            // Remove the values passed in from the value array. Use array_values() to
            // ensure that the array index remains sequential.
            $classes = array_values(array_diff($this->storage['class']
                ->value(), $classes));
            $this->storage['class']
                ->exchangeArray($classes);
        }
        return $this;
    }
    
    /**
     * Gets the class attribute value if set.
     *
     * This method is implemented to take precedence over hasClass() for Twig 2.0.
     *
     * @return \Drupal\Core\Template\AttributeValueBase
     *   The class attribute value if set.
     *
     * @see twig_get_attribute()
     */
    public function getClass() {
        return $this->offsetGet('class');
    }
    
    /**
     * Checks if the class array has the given CSS class.
     *
     * @param string $class
     *   The CSS class to check for.
     *
     * @return bool
     *   Returns TRUE if the class exists, or FALSE otherwise.
     */
    public function hasClass($class) {
        if (isset($this->storage['class']) && $this->storage['class'] instanceof AttributeArray) {
            return in_array($class, $this->storage['class']
                ->value());
        }
        else {
            return FALSE;
        }
    }
    
    /**
     * Implements the magic __toString() method.
     */
    public function __toString() {
        $return = '';
        
        /** @var \Drupal\Core\Template\AttributeValueBase $value */
        foreach ($this->storage as $value) {
            $rendered = $value->render();
            if ($rendered) {
                $return .= ' ' . $rendered;
            }
        }
        return $return;
    }
    
    /**
     * Returns all storage elements as an array.
     *
     * @return array
     *   An associative array of attributes.
     */
    public function toArray() {
        $return = [];
        foreach ($this->storage as $name => $value) {
            $return[$name] = $value->value();
        }
        return $return;
    }
    
    /**
     * Implements the magic __clone() method.
     */
    public function __clone() {
        foreach ($this->storage as $name => $value) {
            $this->storage[$name] = clone $value;
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIterator() {
        return new \ArrayIterator($this->storage);
    }
    
    /**
     * Returns the whole array.
     */
    public function storage() {
        return $this->storage;
    }
    
    /**
     * Returns a representation of the object for use in JSON serialization.
     *
     * @return string
     *   The safe string content.
     */
    public function jsonSerialize() {
        return (string) $this;
    }
    
    /**
     * Merges an Attribute object into the current storage.
     *
     * @param \Drupal\Core\Template\Attribute $collection
     *   The Attribute object to merge.
     *
     * @return $this
     */
    public function merge(Attribute $collection) {
        $merged_attributes = NestedArray::mergeDeep($this->toArray(), $collection->toArray());
        foreach ($merged_attributes as $name => $value) {
            $this->storage[$name] = $this->createAttributeValue($name, $value);
        }
        return $this;
    }

}