<?php

/**

 * Blocks API: WP_Block_List class

 *

 * @package WordPress

 * @since 5.5.0

 */

/**

 * Class representing a list of block instances.

 *

 * @since 5.5.0

 */

class WP_Block_List implements Iterator, ArrayAccess, Countable {

	/**

	 * Original array of parsed block data, or block instances.

	 *

	 * @since 5.5.0

	 * @var array[]|WP_Block[]

	 * @access protected

	 */

	protected $blocks;

	/**

	 * All available context of the current hierarchy.

	 *

	 * @since 5.5.0

	 * @var array

	 * @access protected

	 */

	protected $available_context;

	/**

	 * Block type registry to use in constructing block instances.

	 *

	 * @since 5.5.0

	 * @var WP_Block_Type_Registry

	 * @access protected

	 */

	protected $registry;

	/**

	 * Constructor.

	 *

	 * Populates object properties from the provided block instance argument.

	 *

	 * @since 5.5.0

	 *

	 * @param array[]|WP_Block[]     $blocks            Array of parsed block data, or block instances.

	 * @param array                  $available_context Optional array of ancestry context values.

	 * @param WP_Block_Type_Registry $registry          Optional block type registry.

	 */

	public function __construct( $blocks, $available_context = array(), $registry = null ) {

		if ( ! $registry instanceof WP_Block_Type_Registry ) {

			$registry = WP_Block_Type_Registry::get_instance();

		}

		$this->blocks            = $blocks;

		$this->available_context = $available_context;

		$this->registry          = $registry;

	}

	/**

	 * Returns true if a block exists by the specified block index, or false

	 * otherwise.

	 *

	 * @since 5.5.0

	 *

	 * @link https://www.php.net/manual/en/arrayaccess.offsetexists.php

	 *

	 * @param string $index Index of block to check.

	 * @return bool Whether block exists.

	 */

	public function offsetExists( $index ) {

		return isset( $this->blocks[ $index ] );

	}

	/**

	 * Returns the value by the specified block index.

	 *

	 * @since 5.5.0

	 *

	 * @link https://www.php.net/manual/en/arrayaccess.offsetget.php

	 *

	 * @param string $index Index of block value to retrieve.

	 * @return mixed|null Block value if exists, or null.

	 */

	public function offsetGet( $index ) {

		$block = $this->blocks[ $index ];

		if ( isset( $block ) && is_array( $block ) ) {

			$block                  = new WP_Block( $block, $this->available_context, $this->registry );

			$this->blocks[ $index ] = $block;

		}

		return $block;

	}

	/**

	 * Assign a block value by the specified block index.

	 *

	 * @since 5.5.0

	 *

	 * @link https://www.php.net/manual/en/arrayaccess.offsetset.php

	 *

	 * @param string $index Index of block value to set.

	 * @param mixed  $value Block value.

	 */

	public function offsetSet( $index, $value ) {

		if ( is_null( $index ) ) {

			$this->blocks[] = $value;

		} else {

			$this->blocks[ $index ] = $value;

		}

	}

	/**

	 * Unset a block.

	 *

	 * @since 5.5.0

	 *

	 * @link https://www.php.net/manual/en/arrayaccess.offsetunset.php

	 *

	 * @param string $index Index of block value to unset.

	 */

	public function offsetUnset( $index ) {

		unset( $this->blocks[ $index ] );

	}

	/**

	 * Rewinds back to the first element of the Iterator.

	 *

	 * @since 5.5.0

	 *

	 * @link https://www.php.net/manual/en/iterator.rewind.php

	 */

	public function rewind() {

		reset( $this->blocks );

	}

	/**

	 * Returns the current element of the block list.

	 *

	 * @since 5.5.0

	 *

	 * @link https://www.php.net/manual/en/iterator.current.php

	 *

	 * @return mixed Current element.

	 */

	public function current() {

		return $this->offsetGet( $this->key() );

	}

	/**

	 * Returns the key of the current element of the block list.

	 *

	 * @since 5.5.0

	 *

	 * @link https://www.php.net/manual/en/iterator.key.php

	 *

	 * @return mixed Key of the current element.

	 */

	public function key() {

		return key( $this->blocks );

	}

	/**

	 * Moves the current position of the block list to the next element.

	 *

	 * @since 5.5.0

	 *

	 * @link https://www.php.net/manual/en/iterator.next.php

	 */

	public function next() {

		next( $this->blocks );

	}

	/**

	 * Checks if current position is valid.

	 *

	 * @since 5.5.0

	 *

	 * @link https://www.php.net/manual/en/iterator.valid.php

	 */

	public function valid() {

		return null !== key( $this->blocks );

	}

	/**

	 * Returns the count of blocks in the list.

	 *

	 * @since 5.5.0

	 *

	 * @link https://www.php.net/manual/en/countable.count.php

	 *

	 * @return int Block count.

	 */

	public function count() {

		return count( $this->blocks );

	}

}