<?php

/**

 * Server-side rendering of the `core/categories` block.

 *

 * @package WordPress

 */

/**

 * Renders the `core/categories` block on server.

 *

 * @param array $attributes The block attributes.

 *

 * @return string Returns the categories list/dropdown markup.

 */

function render_block_core_categories( $attributes ) {

	static $block_id = 0;

	$args = array(

		'echo'         => false,

		'hierarchical' => ! empty( $attributes['showHierarchy'] ),

		'orderby'      => 'name',

		'show_count'   => ! empty( $attributes['showPostCounts'] ),

		'title_li'     => '',

	);

	if ( ! empty( $attributes['showOnlyTopLevel'] ) && $attributes['showOnlyTopLevel'] ) {

		$args['parent'] = 0;

	}

	if ( ! empty( $attributes['displayAsDropdown'] ) ) {

		$id                       = 'wp-block-categories-' . $block_id;

		$args['id']               = $id;

		$args['show_option_none'] = __( 'Select Category' );

		$wrapper_markup           = '<div %1$s><label class="screen-reader-text" for="' . esc_attr( $id ) . '">' . __( 'Categories' ) . '</label>%2$s</div>';

		$items_markup             = wp_dropdown_categories( $args );

		$type                     = 'dropdown';

		if ( ! is_admin() ) {

			// Inject the dropdown script immediately after the select dropdown.

			$items_markup = preg_replace(

				'#(?<=</select>)#',

				build_dropdown_script_block_core_categories( $id ),

				$items_markup,

				1

			);

		}

	} else {

		$wrapper_markup = '<ul %1$s>%2$s</ul>';

		$items_markup   = wp_list_categories( $args );

		$type           = 'list';

	}

	$wrapper_attributes = get_block_wrapper_attributes( array( 'class' => "wp-block-categories-{$type}" ) );

	return sprintf(

		$wrapper_markup,

		$wrapper_attributes,

		$items_markup

	);

}

/**

 * Generates the inline script for a categories dropdown field.

 *

 * @param string $dropdown_id ID of the dropdown field.

 *

 * @return string Returns the dropdown onChange redirection script.

 */

function build_dropdown_script_block_core_categories( $dropdown_id ) {

	ob_start();

	?>

	( function() {

		var dropdown = document.getElementById( '<?php echo esc_js( $dropdown_id ); ?>' );

		function onCatChange() {

			if ( dropdown.options[ dropdown.selectedIndex ].value > 0 ) {

			}

		}

		dropdown.onchange = onCatChange;

	})();

	</script>

	<?php

}

/**

 * Registers the `core/categories` block on server.

 */

function register_block_core_categories() {

	register_block_type_from_metadata(

		__DIR__ . '/categories',

		array(

			'render_callback' => 'render_block_core_categories',

		)

	);

}

add_action( 'init', 'register_block_core_categories' );