WordPress/wp-includes/blocks.php

<?php
/**
 * Functions related to registering and parsing blocks.
 *
 * @package WordPress
 * @subpackage Blocks
 * @since 5.0.0
 */

/**
 * Removes the block asset's path prefix if provided.
 *
 * @since 5.5.0
 *
 * @param string $asset_handle_or_path Asset handle or prefixed path.
 * @return string Path without the prefix or the original value.
 */
function remove_block_asset_path_prefix( $asset_handle_or_path ) {
	$path_prefix = 'file:';
	if ( 0 !== strpos( $asset_handle_or_path, $path_prefix ) ) {
		return $asset_handle_or_path;
	}
	$path = substr(
		$asset_handle_or_path,
		strlen( $path_prefix )
	);
	if ( strpos( $path, './' ) === 0 ) {
		$path = substr( $path, 2 );
	}
	return $path;
}

/**
 * Generates the name for an asset based on the name of the block
 * and the field name provided.
 *
 * @since 5.5.0
 * @since 6.1.0 Added `$index` parameter.
 *
 * @param string $block_name Name of the block.
 * @param string $field_name Name of the metadata field.
 * @param int    $index      Optional. Index of the asset when multiple items passed.
 *                           Default 0.
 * @return string Generated asset name for the block's field.
 */
function generate_block_asset_handle( $block_name, $field_name, $index = 0 ) {
	if ( 0 === strpos( $block_name, 'core/' ) ) {
		$asset_handle = str_replace( 'core/', 'wp-block-', $block_name );
		if ( 0 === strpos( $field_name, 'editor' ) ) {
			$asset_handle .= '-editor';
		}
		if ( 0 === strpos( $field_name, 'view' ) ) {
			$asset_handle .= '-view';
		}
		if ( $index > 0 ) {
			$asset_handle .= '-' . ( $index + 1 );
		}
		return $asset_handle;
	}

	$field_mappings = array(
		'editorScript' => 'editor-script',
		'script'       => 'script',
		'viewScript'   => 'view-script',
		'editorStyle'  => 'editor-style',
		'style'        => 'style',
	);
	$asset_handle   = str_replace( '/', '-', $block_name ) .
		'-' . $field_mappings[ $field_name ];
	if ( $index > 0 ) {
		$asset_handle .= '-' . ( $index + 1 );
	}
	return $asset_handle;
}

/**
 * Finds a script handle for the selected block metadata field. It detects
 * when a path to file was provided and finds a corresponding asset file
 * with details necessary to register the script under automatically
 * generated handle name. It returns unprocessed script handle otherwise.
 *
 * @since 5.5.0
 * @since 6.1.0 Added `$index` parameter.
 *
 * @param array  $metadata   Block metadata.
 * @param string $field_name Field name to pick from metadata.
 * @param int    $index      Optional. Index of the script to register when multiple items passed.
 *                           Default 0.
 * @return string|false Script handle provided directly or created through
 *                      script's registration, or false on failure.
 */
function register_block_script_handle( $metadata, $field_name, $index = 0 ) {
	if ( empty( $metadata[ $field_name ] ) ) {
		return false;
	}

	$script_handle = $metadata[ $field_name ];
	if ( is_array( $script_handle ) ) {
		if ( empty( $script_handle[ $index ] ) ) {
			return false;
		}
		$script_handle = $script_handle[ $index ];
	}

	$script_path = remove_block_asset_path_prefix( $script_handle );
	if ( $script_handle === $script_path ) {
		return $script_handle;
	}

	$script_handle     = generate_block_asset_handle( $metadata['name'], $field_name, $index );
	$script_asset_path = wp_normalize_path(
		realpath(
			dirname( $metadata['file'] ) . '/' .
			substr_replace( $script_path, '.asset.php', - strlen( '.js' ) )
		)
	);
	if ( ! file_exists( $script_asset_path ) ) {
		_doing_it_wrong(
			__FUNCTION__,
			sprintf(
				/* translators: 1: Field name, 2: Block name. */
				__( 'The asset file for the "%1$s" defined in "%2$s" block definition is missing.' ),
				$field_name,
				$metadata['name']
			),
			'5.5.0'
		);
		return false;
	}

	// Path needs to be normalized to work in Windows env.
	static $wpinc_path_norm = '';
	if ( ! $wpinc_path_norm ) {
		$wpinc_path_norm = wp_normalize_path( realpath( ABSPATH . WPINC ) );
	}

	$theme_path_norm  = wp_normalize_path( get_theme_file_path() );
	$script_path_norm = wp_normalize_path( realpath( dirname( $metadata['file'] ) . '/' . $script_path ) );

	$is_core_block  = isset( $metadata['file'] ) && 0 === strpos( $metadata['file'], $wpinc_path_norm );
	$is_theme_block = 0 === strpos( $script_path_norm, $theme_path_norm );

	$script_uri = plugins_url( $script_path, $metadata['file'] );
	if ( $is_core_block ) {
		$script_uri = includes_url( str_replace( $wpinc_path_norm, '', $script_path_norm ) );
	} elseif ( $is_theme_block ) {
		$script_uri = get_theme_file_uri( str_replace( $theme_path_norm, '', $script_path_norm ) );
	}

	$script_asset        = require $script_asset_path;
	$script_dependencies = isset( $script_asset['dependencies'] ) ? $script_asset['dependencies'] : array();
	$result              = wp_register_script(
		$script_handle,
		$script_uri,
		$script_dependencies,
		isset( $script_asset['version'] ) ? $script_asset['version'] : false
	);
	if ( ! $result ) {
		return false;
	}

	if ( ! empty( $metadata['textdomain'] ) && in_array( 'wp-i18n', $script_dependencies, true ) ) {
		wp_set_script_translations( $script_handle, $metadata['textdomain'] );
	}

	return $script_handle;
}

/**
 * Finds a style handle for the block metadata field. It detects when a path
 * to file was provided and registers the style under automatically
 * generated handle name. It returns unprocessed style handle otherwise.
 *
 * @since 5.5.0
 * @since 6.1.0 Added `$index` parameter.
 *
 * @param array  $metadata   Block metadata.
 * @param string $field_name Field name to pick from metadata.
 * @param int    $index      Optional. Index of the style to register when multiple items passed.
 *                           Default 0.
 * @return string|false Style handle provided directly or created through
 *                      style's registration, or false on failure.
 */
function register_block_style_handle( $metadata, $field_name, $index = 0 ) {
	if ( empty( $metadata[ $field_name ] ) ) {
		return false;
	}

	static $wpinc_path_norm = '';
	if ( ! $wpinc_path_norm ) {
		$wpinc_path_norm = wp_normalize_path( realpath( ABSPATH . WPINC ) );
	}

	$is_core_block = isset( $metadata['file'] ) && 0 === strpos( $metadata['file'], $wpinc_path_norm );
	// Skip registering individual styles for each core block when a bundled version provided.
	if ( $is_core_block && ! wp_should_load_separate_core_block_assets() ) {
		return false;
	}

	$style_handle = $metadata[ $field_name ];
	if ( is_array( $style_handle ) ) {
		if ( empty( $style_handle[ $index ] ) ) {
			return false;
		}
		$style_handle = $style_handle[ $index ];
	}

	$style_path      = remove_block_asset_path_prefix( $style_handle );
	$is_style_handle = $style_handle === $style_path;
	// Allow only passing style handles for core blocks.
	if ( $is_core_block && ! $is_style_handle ) {
		return false;
	}
	// Return the style handle unless it's the first item for every core block that requires special treatment.
	if ( $is_style_handle && ! ( $is_core_block && 0 === $index ) ) {
		return $style_handle;
	}

	// Check whether styles should have a ".min" suffix or not.
	$suffix = SCRIPT_DEBUG ? '' : '.min';
	if ( $is_core_block ) {
		$style_path = "style$suffix.css";
	}

	$style_path_norm = wp_normalize_path( realpath( dirname( $metadata['file'] ) . '/' . $style_path ) );
	$has_style_file  = '' !== $style_path_norm;

	if ( $has_style_file ) {
		$style_uri = plugins_url( $style_path, $metadata['file'] );

		// Cache $theme_path_norm to avoid calling get_theme_file_path() multiple times.
		static $theme_path_norm = '';
		if ( ! $theme_path_norm ) {
			$theme_path_norm = wp_normalize_path( get_theme_file_path() );
		}

		$is_theme_block = str_starts_with( $style_path_norm, $theme_path_norm );

		if ( $is_theme_block ) {
			$style_uri = get_theme_file_uri( str_replace( $theme_path_norm, '', $style_path_norm ) );
		} elseif ( $is_core_block ) {
			$style_uri = includes_url( 'blocks/' . str_replace( 'core/', '', $metadata['name'] ) . "/style$suffix.css" );
		}
	} else {
		$style_uri = false;
	}

	$style_handle = generate_block_asset_handle( $metadata['name'], $field_name, $index );
	$version      = ! $is_core_block && isset( $metadata['version'] ) ? $metadata['version'] : false;
	$result       = wp_register_style(
		$style_handle,
		$style_uri,
		array(),
		$version
	);
	if ( ! $result ) {
		return false;
	}

	if ( $has_style_file ) {
		wp_style_add_data( $style_handle, 'path', $style_path_norm );

		$rtl_file = str_replace( "{$suffix}.css", "-rtl{$suffix}.css", $style_path_norm );

		if ( is_rtl() && file_exists( $rtl_file ) ) {
			wp_style_add_data( $style_handle, 'rtl', 'replace' );
			wp_style_add_data( $style_handle, 'suffix', $suffix );
			wp_style_add_data( $style_handle, 'path', $rtl_file );
		}
	}

	return $style_handle;
}

/**
 * Gets i18n schema for block's metadata read from `block.json` file.
 *
 * @since 5.9.0
 *
 * @return object The schema for block's metadata.
 */
function get_block_metadata_i18n_schema() {
	static $i18n_block_schema;

	if ( ! isset( $i18n_block_schema ) ) {
		$i18n_block_schema = wp_json_file_decode( __DIR__ . '/block-i18n.json' );
	}

	return $i18n_block_schema;
}

/**
 * Registers a block type from the metadata stored in the `block.json` file.
 *
 * @since 5.5.0
 * @since 5.7.0 Added support for `textdomain` field and i18n handling for all translatable fields.
 * @since 5.9.0 Added support for `variations` and `viewScript` fields.
 * @since 6.1.0 Added support for `render` field.
 *
 * @param string $file_or_folder Path to the JSON file with metadata definition for
 *                               the block or path to the folder where the `block.json` file is located.
 *                               If providing the path to a JSON file, the filename must end with `block.json`.
 * @param array  $args           Optional. Array of block type arguments. Accepts any public property
 *                               of `WP_Block_Type`. See WP_Block_Type::__construct() for information
 *                               on accepted arguments. Default empty array.
 * @return WP_Block_Type|false The registered block type on success, or false on failure.
 */
function register_block_type_from_metadata( $file_or_folder, $args = array() ) {
	/*
	 * Get an array of metadata from a PHP file.
	 * This improves performance for core blocks as it's only necessary to read a single PHP file
	 * instead of reading a JSON file per-block, and then decoding from JSON to PHP.
	 * Using a static variable ensures that the metadata is only read once per request.
	 */
	static $core_blocks_meta;
	if ( ! $core_blocks_meta ) {
		$core_blocks_meta = include_once ABSPATH . WPINC . '/blocks/blocks-json.php';
	}

	$metadata_file = ( ! str_ends_with( $file_or_folder, 'block.json' ) ) ?
		trailingslashit( $file_or_folder ) . 'block.json' :
		$file_or_folder;

	if ( ! file_exists( $metadata_file ) ) {
		return false;
	}

	// Try to get metadata from the static cache for core blocks.
	$metadata = false;
	if ( str_starts_with( $file_or_folder, ABSPATH . WPINC ) ) {
		$core_block_name = str_replace( ABSPATH . WPINC . '/blocks/', '', $file_or_folder );
		if ( ! empty( $core_blocks_meta[ $core_block_name ] ) ) {
			$metadata = $core_blocks_meta[ $core_block_name ];
		}
	}

	// If metadata is not found in the static cache, read it from the file.
	if ( ! $metadata ) {
		$metadata = wp_json_file_decode( $metadata_file, array( 'associative' => true ) );
	}

	if ( ! is_array( $metadata ) || empty( $metadata['name'] ) ) {
		return false;
	}
	$metadata['file'] = wp_normalize_path( realpath( $metadata_file ) );

	/**
	 * Filters the metadata provided for registering a block type.
	 *
	 * @since 5.7.0
	 *
	 * @param array $metadata Metadata for registering a block type.
	 */
	$metadata = apply_filters( 'block_type_metadata', $metadata );

	// Add `style` and `editor_style` for core blocks if missing.
	if ( ! empty( $metadata['name'] ) && 0 === strpos( $metadata['name'], 'core/' ) ) {
		$block_name = str_replace( 'core/', '', $metadata['name'] );

		if ( ! isset( $metadata['style'] ) ) {
			$metadata['style'] = "wp-block-$block_name";
		}
		if ( ! isset( $metadata['editorStyle'] ) ) {
			$metadata['editorStyle'] = "wp-block-{$block_name}-editor";
		}
	}

	$settings          = array();
	$property_mappings = array(
		'apiVersion'      => 'api_version',
		'title'           => 'title',
		'category'        => 'category',
		'parent'          => 'parent',
		'ancestor'        => 'ancestor',
		'icon'            => 'icon',
		'description'     => 'description',
		'keywords'        => 'keywords',
		'attributes'      => 'attributes',
		'providesContext' => 'provides_context',
		'usesContext'     => 'uses_context',
		'supports'        => 'supports',
		'styles'          => 'styles',
		'variations'      => 'variations',
		'example'         => 'example',
	);
	$textdomain        = ! empty( $metadata['textdomain'] ) ? $metadata['textdomain'] : null;
	$i18n_schema       = get_block_metadata_i18n_schema();

	foreach ( $property_mappings as $key => $mapped_key ) {
		if ( isset( $metadata[ $key ] ) ) {
			$settings[ $mapped_key ] = $metadata[ $key ];
			if ( $textdomain && isset( $i18n_schema->$key ) ) {
				$settings[ $mapped_key ] = translate_settings_using_i18n_schema( $i18n_schema->$key, $settings[ $key ], $textdomain );
			}
		}
	}

	$script_fields = array(
		'editorScript' => 'editor_script_handles',
		'script'       => 'script_handles',
		'viewScript'   => 'view_script_handles',
	);
	foreach ( $script_fields as $metadata_field_name => $settings_field_name ) {
		if ( ! empty( $metadata[ $metadata_field_name ] ) ) {
			$scripts           = $metadata[ $metadata_field_name ];
			$processed_scripts = array();
			if ( is_array( $scripts ) ) {
				for ( $index = 0; $index < count( $scripts ); $index++ ) {
					$result = register_block_script_handle(
						$metadata,
						$metadata_field_name,
						$index
					);
					if ( $result ) {
						$processed_scripts[] = $result;
					}
				}
			} else {
				$result = register_block_script_handle(
					$metadata,
					$metadata_field_name
				);
				if ( $result ) {
					$processed_scripts[] = $result;
				}
			}
			$settings[ $settings_field_name ] = $processed_scripts;
		}
	}

	$style_fields = array(
		'editorStyle' => 'editor_style_handles',
		'style'       => 'style_handles',
	);
	foreach ( $style_fields as $metadata_field_name => $settings_field_name ) {
		if ( ! empty( $metadata[ $metadata_field_name ] ) ) {
			$styles           = $metadata[ $metadata_field_name ];
			$processed_styles = array();
			if ( is_array( $styles ) ) {
				for ( $index = 0; $index < count( $styles ); $index++ ) {
					$result = register_block_style_handle(
						$metadata,
						$metadata_field_name,
						$index
					);
					if ( $result ) {
						$processed_styles[] = $result;
					}
				}
			} else {
				$result = register_block_style_handle(
					$metadata,
					$metadata_field_name
				);
				if ( $result ) {
					$processed_styles[] = $result;
				}
			}
			$settings[ $settings_field_name ] = $processed_styles;
		}
	}

	if ( ! empty( $metadata['render'] ) ) {
		$template_path = wp_normalize_path(
			realpath(
				dirname( $metadata['file'] ) . '/' .
				remove_block_asset_path_prefix( $metadata['render'] )
			)
		);
		if ( $template_path ) {
			/**
			 * Renders the block on the server.
			 *
			 * @since 6.1.0
			 *
			 * @param array    $attributes Block attributes.
			 * @param string   $content    Block default content.
			 * @param WP_Block $block      Block instance.
			 *
			 * @return string Returns the block content.
			 */
			$settings['render_callback'] = function( $attributes, $content, $block ) use ( $template_path ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
				ob_start();
				require $template_path;
				return ob_get_clean();
			};
		}
	}

	/**
	 * Filters the settings determined from the block type metadata.
	 *
	 * @since 5.7.0
	 *
	 * @param array $settings Array of determined settings for registering a block type.
	 * @param array $metadata Metadata provided for registering a block type.
	 */
	$settings = apply_filters(
		'block_type_metadata_settings',
		array_merge(
			$settings,
			$args
		),
		$metadata
	);

	return WP_Block_Type_Registry::get_instance()->register(
		$metadata['name'],
		$settings
	);
}

/**
 * Registers a block type. The recommended way is to register a block type using
 * the metadata stored in the `block.json` file.
 *
 * @since 5.0.0
 * @since 5.8.0 First parameter now accepts a path to the `block.json` file.
 *
 * @param string|WP_Block_Type $block_type Block type name including namespace, or alternatively
 *                                         a path to the JSON file with metadata definition for the block,
 *                                         or a path to the folder where the `block.json` file is located,
 *                                         or a complete WP_Block_Type instance.
 *                                         In case a WP_Block_Type is provided, the $args parameter will be ignored.
 * @param array                $args       Optional. Array of block type arguments. Accepts any public property
 *                                         of `WP_Block_Type`. See WP_Block_Type::__construct() for information
 *                                         on accepted arguments. Default empty array.
 *
 * @return WP_Block_Type|false The registered block type on success, or false on failure.
 */
function register_block_type( $block_type, $args = array() ) {
	if ( is_string( $block_type ) && file_exists( $block_type ) ) {
		return register_block_type_from_metadata( $block_type, $args );
	}

	return WP_Block_Type_Registry::get_instance()->register( $block_type, $args );
}

/**
 * Unregisters a block type.
 *
 * @since 5.0.0
 *
 * @param string|WP_Block_Type $name Block type name including namespace, or alternatively
 *                                   a complete WP_Block_Type instance.
 * @return WP_Block_Type|false The unregistered block type on success, or false on failure.
 */
function unregister_block_type( $name ) {
	return WP_Block_Type_Registry::get_instance()->unregister( $name );
}

/**
 * Determines whether a post or content string has blocks.
 *
 * This test optimizes for performance rather than strict accuracy, detecting
 * the pattern of a block but not validating its structure. For strict accuracy,
 * you should use the block parser on post content.
 *
 * @since 5.0.0
 *
 * @see parse_blocks()
 *
 * @param int|string|WP_Post|null $post Optional. Post content, post ID, or post object.
 *                                      Defaults to global $post.
 * @return bool Whether the post has blocks.
 */
function has_blocks( $post = null ) {
	if ( ! is_string( $post ) ) {
		$wp_post = get_post( $post );

		if ( ! $wp_post instanceof WP_Post ) {
			return false;
		}

		$post = $wp_post->post_content;
	}

	return false !== strpos( (string) $post, '<!-- wp:' );
}

/**
 * Determines whether a $post or a string contains a specific block type.
 *
 * This test optimizes for performance rather than strict accuracy, detecting
 * whether the block type exists but not validating its structure and not checking
 * reusable blocks. For strict accuracy, you should use the block parser on post content.
 *
 * @since 5.0.0
 *
 * @see parse_blocks()
 *
 * @param string                  $block_name Full block type to look for.
 * @param int|string|WP_Post|null $post       Optional. Post content, post ID, or post object.
 *                                            Defaults to global $post.
 * @return bool Whether the post content contains the specified block.
 */
function has_block( $block_name, $post = null ) {
	if ( ! has_blocks( $post ) ) {
		return false;
	}

	if ( ! is_string( $post ) ) {
		$wp_post = get_post( $post );
		if ( $wp_post instanceof WP_Post ) {
			$post = $wp_post->post_content;
		}
	}

	/*
	 * Normalize block name to include namespace, if provided as non-namespaced.
	 * This matches behavior for WordPress 5.0.0 - 5.3.0 in matching blocks by
	 * their serialized names.
	 */
	if ( false === strpos( $block_name, '/' ) ) {
		$block_name = 'core/' . $block_name;
	}

	// Test for existence of block by its fully qualified name.
	$has_block = false !== strpos( $post, '<!-- wp:' . $block_name . ' ' );

	if ( ! $has_block ) {
		/*
		 * If the given block name would serialize to a different name, test for
		 * existence by the serialized form.
		 */
		$serialized_block_name = strip_core_block_namespace( $block_name );
		if ( $serialized_block_name !== $block_name ) {
			$has_block = false !== strpos( $post, '<!-- wp:' . $serialized_block_name . ' ' );
		}
	}

	return $has_block;
}

/**
 * Returns an array of the names of all registered dynamic block types.
 *
 * @since 5.0.0
 *
 * @return string[] Array of dynamic block names.
 */
function get_dynamic_block_names() {
	$dynamic_block_names = array();

	$block_types = WP_Block_Type_Registry::get_instance()->get_all_registered();
	foreach ( $block_types as $block_type ) {
		if ( $block_type->is_dynamic() ) {
			$dynamic_block_names[] = $block_type->name;
		}
	}

	return $dynamic_block_names;
}

/**
 * Given an array of attributes, returns a string in the serialized attributes
 * format prepared for post content.
 *
 * The serialized result is a JSON-encoded string, with unicode escape sequence
 * substitution for characters which might otherwise interfere with embedding
 * the result in an HTML comment.
 *
 * This function must produce output that remains in sync with the output of
 * the serializeAttributes JavaScript function in the block editor in order
 * to ensure consistent operation between PHP and JavaScript.
 *
 * @since 5.3.1
 *
 * @param array $block_attributes Attributes object.
 * @return string Serialized attributes.
 */
function serialize_block_attributes( $block_attributes ) {
	$encoded_attributes = wp_json_encode( $block_attributes, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE );
	$encoded_attributes = preg_replace( '/--/', '\\u002d\\u002d', $encoded_attributes );
	$encoded_attributes = preg_replace( '/</', '\\u003c', $encoded_attributes );
	$encoded_attributes = preg_replace( '/>/', '\\u003e', $encoded_attributes );
	$encoded_attributes = preg_replace( '/&/', '\\u0026', $encoded_attributes );
	// Regex: /\\"/
	$encoded_attributes = preg_replace( '/\\\\"/', '\\u0022', $encoded_attributes );

	return $encoded_attributes;
}

/**
 * Returns the block name to use for serialization. This will remove the default
 * "core/" namespace from a block name.
 *
 * @since 5.3.1
 *
 * @param string|null $block_name Optional. Original block name. Null if the block name is unknown,
 *                                e.g. Classic blocks have their name set to null. Default null.
 * @return string Block name to use for serialization.
 */
function strip_core_block_namespace( $block_name = null ) {
	if ( is_string( $block_name ) && 0 === strpos( $block_name, 'core/' ) ) {
		return substr( $block_name, 5 );
	}

	return $block_name;
}

/**
 * Returns the content of a block, including comment delimiters.
 *
 * @since 5.3.1
 *
 * @param string|null $block_name       Block name. Null if the block name is unknown,
 *                                      e.g. Classic blocks have their name set to null.
 * @param array       $block_attributes Block attributes.
 * @param string      $block_content    Block save content.
 * @return string Comment-delimited block content.
 */
function get_comment_delimited_block_content( $block_name, $block_attributes, $block_content ) {
	if ( is_null( $block_name ) ) {
		return $block_content;
	}

	$serialized_block_name = strip_core_block_namespace( $block_name );
	$serialized_attributes = empty( $block_attributes ) ? '' : serialize_block_attributes( $block_attributes ) . ' ';

	if ( empty( $block_content ) ) {
		return sprintf( '<!-- wp:%s %s/-->', $serialized_block_name, $serialized_attributes );
	}

	return sprintf(
		'<!-- wp:%s %s-->%s<!-- /wp:%s -->',
		$serialized_block_name,
		$serialized_attributes,
		$block_content,
		$serialized_block_name
	);
}

/**
 * Returns the content of a block, including comment delimiters, serializing all
 * attributes from the given parsed block.
 *
 * This should be used when preparing a block to be saved to post content.
 * Prefer `render_block` when preparing a block for display. Unlike
 * `render_block`, this does not evaluate a block's `render_callback`, and will
 * instead preserve the markup as parsed.
 *
 * @since 5.3.1
 *
 * @param array $block A representative array of a single parsed block object. See WP_Block_Parser_Block.
 * @return string String of rendered HTML.
 */
function serialize_block( $block ) {
	$block_content = '';

	$index = 0;
	foreach ( $block['innerContent'] as $chunk ) {
		$block_content .= is_string( $chunk ) ? $chunk : serialize_block( $block['innerBlocks'][ $index++ ] );
	}

	if ( ! is_array( $block['attrs'] ) ) {
		$block['attrs'] = array();
	}

	return get_comment_delimited_block_content(
		$block['blockName'],
		$block['attrs'],
		$block_content
	);
}

/**
 * Returns a joined string of the aggregate serialization of the given
 * parsed blocks.
 *
 * @since 5.3.1
 *
 * @param array[] $blocks An array of representative arrays of parsed block objects. See serialize_block().
 * @return string String of rendered HTML.
 */
function serialize_blocks( $blocks ) {
	return implode( '', array_map( 'serialize_block', $blocks ) );
}

/**
 * Filters and sanitizes block content to remove non-allowable HTML
 * from parsed block attribute values.
 *
 * @since 5.3.1
 *
 * @param string         $text              Text that may contain block content.
 * @param array[]|string $allowed_html      Optional. An array of allowed HTML elements and attributes,
 *                                          or a context name such as 'post'. See wp_kses_allowed_html()
 *                                          for the list of accepted context names. Default 'post'.
 * @param string[]       $allowed_protocols Optional. Array of allowed URL protocols.
 *                                          Defaults to the result of wp_allowed_protocols().
 * @return string The filtered and sanitized content result.
 */
function filter_block_content( $text, $allowed_html = 'post', $allowed_protocols = array() ) {
	$result = '';

	$blocks = parse_blocks( $text );
	foreach ( $blocks as $block ) {
		$block   = filter_block_kses( $block, $allowed_html, $allowed_protocols );
		$result .= serialize_block( $block );
	}

	return $result;
}

/**
 * Filters and sanitizes a parsed block to remove non-allowable HTML
 * from block attribute values.
 *
 * @since 5.3.1
 *
 * @param WP_Block_Parser_Block $block             The parsed block object.
 * @param array[]|string        $allowed_html      An array of allowed HTML elements and attributes,
 *                                                 or a context name such as 'post'. See wp_kses_allowed_html()
 *                                                 for the list of accepted context names.
 * @param string[]              $allowed_protocols Optional. Array of allowed URL protocols.
 *                                                 Defaults to the result of wp_allowed_protocols().
 * @return array The filtered and sanitized block object result.
 */
function filter_block_kses( $block, $allowed_html, $allowed_protocols = array() ) {
	$block['attrs'] = filter_block_kses_value( $block['attrs'], $allowed_html, $allowed_protocols );

	if ( is_array( $block['innerBlocks'] ) ) {
		foreach ( $block['innerBlocks'] as $i => $inner_block ) {
			$block['innerBlocks'][ $i ] = filter_block_kses( $inner_block, $allowed_html, $allowed_protocols );
		}
	}

	return $block;
}

/**
 * Filters and sanitizes a parsed block attribute value to remove
 * non-allowable HTML.
 *
 * @since 5.3.1
 *
 * @param string[]|string $value             The attribute value to filter.
 * @param array[]|string  $allowed_html      An array of allowed HTML elements and attributes,
 *                                           or a context name such as 'post'. See wp_kses_allowed_html()
 *                                           for the list of accepted context names.
 * @param string[]        $allowed_protocols Optional. Array of allowed URL protocols.
 *                                           Defaults to the result of wp_allowed_protocols().
 * @return string[]|string The filtered and sanitized result.
 */
function filter_block_kses_value( $value, $allowed_html, $allowed_protocols = array() ) {
	if ( is_array( $value ) ) {
		foreach ( $value as $key => $inner_value ) {
			$filtered_key   = filter_block_kses_value( $key, $allowed_html, $allowed_protocols );
			$filtered_value = filter_block_kses_value( $inner_value, $allowed_html, $allowed_protocols );

			if ( $filtered_key !== $key ) {
				unset( $value[ $key ] );
			}

			$value[ $filtered_key ] = $filtered_value;
		}
	} elseif ( is_string( $value ) ) {
		return wp_kses( $value, $allowed_html, $allowed_protocols );
	}

	return $value;
}

/**
 * Parses blocks out of a content string, and renders those appropriate for the excerpt.
 *
 * As the excerpt should be a small string of text relevant to the full post content,
 * this function renders the blocks that are most likely to contain such text.
 *
 * @since 5.0.0
 *
 * @param string $content The content to parse.
 * @return string The parsed and filtered content.
 */
function excerpt_remove_blocks( $content ) {
	$allowed_inner_blocks = array(
		// Classic blocks have their blockName set to null.
		null,
		'core/freeform',
		'core/heading',
		'core/html',
		'core/list',
		'core/media-text',
		'core/paragraph',
		'core/preformatted',
		'core/pullquote',
		'core/quote',
		'core/table',
		'core/verse',
	);

	$allowed_wrapper_blocks = array(
		'core/columns',
		'core/column',
		'core/group',
	);

	/**
	 * Filters the list of blocks that can be used as wrapper blocks, allowing
	 * excerpts to be generated from the `innerBlocks` of these wrappers.
	 *
	 * @since 5.8.0
	 *
	 * @param string[] $allowed_wrapper_blocks The list of names of allowed wrapper blocks.
	 */
	$allowed_wrapper_blocks = apply_filters( 'excerpt_allowed_wrapper_blocks', $allowed_wrapper_blocks );

	$allowed_blocks = array_merge( $allowed_inner_blocks, $allowed_wrapper_blocks );

	/**
	 * Filters the list of blocks that can contribute to the excerpt.
	 *
	 * If a dynamic block is added to this list, it must not generate another
	 * excerpt, as this will cause an infinite loop to occur.
	 *
	 * @since 5.0.0
	 *
	 * @param string[] $allowed_blocks The list of names of allowed blocks.
	 */
	$allowed_blocks = apply_filters( 'excerpt_allowed_blocks', $allowed_blocks );
	$blocks         = parse_blocks( $content );
	$output         = '';

	foreach ( $blocks as $block ) {
		if ( in_array( $block['blockName'], $allowed_blocks, true ) ) {
			if ( ! empty( $block['innerBlocks'] ) ) {
				if ( in_array( $block['blockName'], $allowed_wrapper_blocks, true ) ) {
					$output .= _excerpt_render_inner_blocks( $block, $allowed_blocks );
					continue;
				}

				// Skip the block if it has disallowed or nested inner blocks.
				foreach ( $block['innerBlocks'] as $inner_block ) {
					if (
						! in_array( $inner_block['blockName'], $allowed_inner_blocks, true ) ||
						! empty( $inner_block['innerBlocks'] )
					) {
						continue 2;
					}
				}
			}

			$output .= render_block( $block );
		}
	}

	return $output;
}

/**
 * Renders inner blocks from the allowed wrapper blocks
 * for generating an excerpt.
 *
 * @since 5.8.0
 * @access private
 *
 * @param array $parsed_block   The parsed block.
 * @param array $allowed_blocks The list of allowed inner blocks.
 * @return string The rendered inner blocks.
 */
function _excerpt_render_inner_blocks( $parsed_block, $allowed_blocks ) {
	$output = '';

	foreach ( $parsed_block['innerBlocks'] as $inner_block ) {
		if ( ! in_array( $inner_block['blockName'], $allowed_blocks, true ) ) {
			continue;
		}

		if ( empty( $inner_block['innerBlocks'] ) ) {
			$output .= render_block( $inner_block );
		} else {
			$output .= _excerpt_render_inner_blocks( $inner_block, $allowed_blocks );
		}
	}

	return $output;
}

/**
 * Renders a single block into a HTML string.
 *
 * @since 5.0.0
 *
 * @global WP_Post $post The post to edit.
 *
 * @param array $parsed_block A single parsed block object.
 * @return string String of rendered HTML.
 */
function render_block( $parsed_block ) {
	global $post;
	$parent_block = null;

	/**
	 * Allows render_block() to be short-circuited, by returning a non-null value.
	 *
	 * @since 5.1.0
	 * @since 5.9.0 The `$parent_block` parameter was added.
	 *
	 * @param string|null   $pre_render   The pre-rendered content. Default null.
	 * @param array         $parsed_block The block being rendered.
	 * @param WP_Block|null $parent_block If this is a nested block, a reference to the parent block.
	 */
	$pre_render = apply_filters( 'pre_render_block', null, $parsed_block, $parent_block );
	if ( ! is_null( $pre_render ) ) {
		return $pre_render;
	}

	$source_block = $parsed_block;

	/**
	 * Filters the block being rendered in render_block(), before it's processed.
	 *
	 * @since 5.1.0
	 * @since 5.9.0 The `$parent_block` parameter was added.
	 *
	 * @param array         $parsed_block The block being rendered.
	 * @param array         $source_block An un-modified copy of $parsed_block, as it appeared in the source content.
	 * @param WP_Block|null $parent_block If this is a nested block, a reference to the parent block.
	 */
	$parsed_block = apply_filters( 'render_block_data', $parsed_block, $source_block, $parent_block );

	$context = array();

	if ( $post instanceof WP_Post ) {
		$context['postId'] = $post->ID;

		/*
		 * The `postType` context is largely unnecessary server-side, since the ID
		 * is usually sufficient on its own. That being said, since a block's
		 * manifest is expected to be shared between the server and the client,
		 * it should be included to consistently fulfill the expectation.
		 */
		$context['postType'] = $post->post_type;
	}

	/**
	 * Filters the default context provided to a rendered block.
	 *
	 * @since 5.5.0
	 * @since 5.9.0 The `$parent_block` parameter was added.
	 *
	 * @param array         $context      Default context.
	 * @param array         $parsed_block Block being rendered, filtered by `render_block_data`.
	 * @param WP_Block|null $parent_block If this is a nested block, a reference to the parent block.
	 */
	$context = apply_filters( 'render_block_context', $context, $parsed_block, $parent_block );

	$block = new WP_Block( $parsed_block, $context );

	return $block->render();
}

/**
 * Parses blocks out of a content string.
 *
 * @since 5.0.0
 *
 * @param string $content Post content.
 * @return array[] Array of parsed block objects.
 */
function parse_blocks( $content ) {
	/**
	 * Filter to allow plugins to replace the server-side block parser.
	 *
	 * @since 5.0.0
	 *
	 * @param string $parser_class Name of block parser class.
	 */
	$parser_class = apply_filters( 'block_parser_class', 'WP_Block_Parser' );

	$parser = new $parser_class();
	return $parser->parse( $content );
}

/**
 * Parses dynamic blocks out of `post_content` and re-renders them.
 *
 * @since 5.0.0
 *
 * @param string $content Post content.
 * @return string Updated post content.
 */
function do_blocks( $content ) {
	$blocks = parse_blocks( $content );
	$output = '';

	foreach ( $blocks as $block ) {
		$output .= render_block( $block );
	}

	// If there are blocks in this content, we shouldn't run wpautop() on it later.
	$priority = has_filter( 'the_content', 'wpautop' );
	if ( false !== $priority && doing_filter( 'the_content' ) && has_blocks( $content ) ) {
		remove_filter( 'the_content', 'wpautop', $priority );
		add_filter( 'the_content', '_restore_wpautop_hook', $priority + 1 );
	}

	return $output;
}

/**
 * If do_blocks() needs to remove wpautop() from the `the_content` filter, this re-adds it afterwards,
 * for subsequent `the_content` usage.
 *
 * @since 5.0.0
 * @access private
 *
 * @param string $content The post content running through this filter.
 * @return string The unmodified content.
 */
function _restore_wpautop_hook( $content ) {
	$current_priority = has_filter( 'the_content', '_restore_wpautop_hook' );

	add_filter( 'the_content', 'wpautop', $current_priority - 1 );
	remove_filter( 'the_content', '_restore_wpautop_hook', $current_priority );

	return $content;
}

/**
 * Returns the current version of the block format that the content string is using.
 *
 * If the string doesn't contain blocks, it returns 0.
 *
 * @since 5.0.0
 *
 * @param string $content Content to test.
 * @return int The block format version is 1 if the content contains one or more blocks, 0 otherwise.
 */
function block_version( $content ) {
	return has_blocks( $content ) ? 1 : 0;
}

/**
 * Registers a new block style.
 *
 * @since 5.3.0
 *
 * @link https://developer.wordpress.org/block-editor/reference-guides/block-api/block-styles/
 *
 * @param string $block_name       Block type name including namespace.
 * @param array  $style_properties Array containing the properties of the style name,
 *                                 label, style (name of the stylesheet to be enqueued),
 *                                 inline_style (string containing the CSS to be added).
 * @return bool True if the block style was registered with success and false otherwise.
 */
function register_block_style( $block_name, $style_properties ) {
	return WP_Block_Styles_Registry::get_instance()->register( $block_name, $style_properties );
}

/**
 * Unregisters a block style.
 *
 * @since 5.3.0
 *
 * @param string $block_name       Block type name including namespace.
 * @param string $block_style_name Block style name.
 * @return bool True if the block style was unregistered with success and false otherwise.
 */
function unregister_block_style( $block_name, $block_style_name ) {
	return WP_Block_Styles_Registry::get_instance()->unregister( $block_name, $block_style_name );
}

/**
 * Checks whether the current block type supports the feature requested.
 *
 * @since 5.8.0
 *
 * @param WP_Block_Type $block_type Block type to check for support.
 * @param array         $feature    Path to a specific feature to check support for.
 * @param mixed         $default    Optional. Fallback value for feature support. Default false.
 * @return bool Whether the feature is supported.
 */
function block_has_support( $block_type, $feature, $default = false ) {
	$block_support = $default;
	if ( $block_type && property_exists( $block_type, 'supports' ) ) {
		$block_support = _wp_array_get( $block_type->supports, $feature, $default );
	}

	return true === $block_support || is_array( $block_support );
}

/**
 * Converts typography keys declared under `supports.*` to `supports.typography.*`.
 *
 * Displays a `_doing_it_wrong()` notice when a block using the older format is detected.
 *
 * @since 5.8.0
 *
 * @param array $metadata Metadata for registering a block type.
 * @return array Filtered metadata for registering a block type.
 */
function wp_migrate_old_typography_shape( $metadata ) {
	if ( ! isset( $metadata['supports'] ) ) {
		return $metadata;
	}

	$typography_keys = array(
		'__experimentalFontFamily',
		'__experimentalFontStyle',
		'__experimentalFontWeight',
		'__experimentalLetterSpacing',
		'__experimentalTextDecoration',
		'__experimentalTextTransform',
		'fontSize',
		'lineHeight',
	);

	foreach ( $typography_keys as $typography_key ) {
		$support_for_key = _wp_array_get( $metadata['supports'], array( $typography_key ), null );

		if ( null !== $support_for_key ) {
			_doing_it_wrong(
				'register_block_type_from_metadata()',
				sprintf(
					/* translators: 1: Block type, 2: Typography supports key, e.g: fontSize, lineHeight, etc. 3: block.json, 4: Old metadata key, 5: New metadata key. */
					__( 'Block "%1$s" is declaring %2$s support in %3$s file under %4$s. %2$s support is now declared under %5$s.' ),
					$metadata['name'],
					"<code>$typography_key</code>",
					'<code>block.json</code>',
					"<code>supports.$typography_key</code>",
					"<code>supports.typography.$typography_key</code>"
				),
				'5.8.0'
			);

			_wp_array_set( $metadata['supports'], array( 'typography', $typography_key ), $support_for_key );
			unset( $metadata['supports'][ $typography_key ] );
		}
	}

	return $metadata;
}

/**
 * Helper function that constructs a WP_Query args array from
 * a `Query` block properties.
 *
 * It's used in Query Loop, Query Pagination Numbers and Query Pagination Next blocks.
 *
 * @since 5.8.0
 * @since 6.1.0 Added `query_loop_block_query_vars` filter and `parents` support in query.
 *
 * @param WP_Block $block Block instance.
 * @param int      $page  Current query's page.
 *
 * @return array Returns the constructed WP_Query arguments.
 */
function build_query_vars_from_query_block( $block, $page ) {
	$query = array(
		'post_type'    => 'post',
		'order'        => 'DESC',
		'orderby'      => 'date',
		'post__not_in' => array(),
	);

	if ( isset( $block->context['query'] ) ) {
		if ( ! empty( $block->context['query']['postType'] ) ) {
			$post_type_param = $block->context['query']['postType'];
			if ( is_post_type_viewable( $post_type_param ) ) {
				$query['post_type'] = $post_type_param;
			}
		}
		if ( isset( $block->context['query']['sticky'] ) && ! empty( $block->context['query']['sticky'] ) ) {
			$sticky = get_option( 'sticky_posts' );
			if ( 'only' === $block->context['query']['sticky'] ) {
				$query['post__in'] = $sticky;
			} else {
				$query['post__not_in'] = array_merge( $query['post__not_in'], $sticky );
			}
		}
		if ( ! empty( $block->context['query']['exclude'] ) ) {
			$excluded_post_ids     = array_map( 'intval', $block->context['query']['exclude'] );
			$excluded_post_ids     = array_filter( $excluded_post_ids );
			$query['post__not_in'] = array_merge( $query['post__not_in'], $excluded_post_ids );
		}
		if (
			isset( $block->context['query']['perPage'] ) &&
			is_numeric( $block->context['query']['perPage'] )
		) {
			$per_page = absint( $block->context['query']['perPage'] );
			$offset   = 0;

			if (
				isset( $block->context['query']['offset'] ) &&
				is_numeric( $block->context['query']['offset'] )
			) {
				$offset = absint( $block->context['query']['offset'] );
			}

			$query['offset']         = ( $per_page * ( $page - 1 ) ) + $offset;
			$query['posts_per_page'] = $per_page;
		}
		// Migrate `categoryIds` and `tagIds` to `tax_query` for backwards compatibility.
		if ( ! empty( $block->context['query']['categoryIds'] ) || ! empty( $block->context['query']['tagIds'] ) ) {
			$tax_query = array();
			if ( ! empty( $block->context['query']['categoryIds'] ) ) {
				$tax_query[] = array(
					'taxonomy'         => 'category',
					'terms'            => array_filter( array_map( 'intval', $block->context['query']['categoryIds'] ) ),
					'include_children' => false,
				);
			}
			if ( ! empty( $block->context['query']['tagIds'] ) ) {
				$tax_query[] = array(
					'taxonomy'         => 'post_tag',
					'terms'            => array_filter( array_map( 'intval', $block->context['query']['tagIds'] ) ),
					'include_children' => false,
				);
			}
			$query['tax_query'] = $tax_query;
		}
		if ( ! empty( $block->context['query']['taxQuery'] ) ) {
			$query['tax_query'] = array();
			foreach ( $block->context['query']['taxQuery'] as $taxonomy => $terms ) {
				if ( is_taxonomy_viewable( $taxonomy ) && ! empty( $terms ) ) {
					$query['tax_query'][] = array(
						'taxonomy'         => $taxonomy,
						'terms'            => array_filter( array_map( 'intval', $terms ) ),
						'include_children' => false,
					);
				}
			}
		}
		if (
			isset( $block->context['query']['order'] ) &&
				in_array( strtoupper( $block->context['query']['order'] ), array( 'ASC', 'DESC' ), true )
		) {
			$query['order'] = strtoupper( $block->context['query']['order'] );
		}
		if ( isset( $block->context['query']['orderBy'] ) ) {
			$query['orderby'] = $block->context['query']['orderBy'];
		}
		if (
			isset( $block->context['query']['author'] ) &&
			(int) $block->context['query']['author'] > 0
		) {
			$query['author'] = (int) $block->context['query']['author'];
		}
		if ( ! empty( $block->context['query']['search'] ) ) {
			$query['s'] = $block->context['query']['search'];
		}
		if ( ! empty( $block->context['query']['parents'] ) && is_post_type_hierarchical( $query['post_type'] ) ) {
			$query['post_parent__in'] = array_filter( array_map( 'intval', $block->context['query']['parents'] ) );
		}
	}

	/**
	 * Filters the arguments which will be passed to `WP_Query` for the Query Loop Block.
	 *
	 * Anything to this filter should be compatible with the `WP_Query` API to form
	 * the query context which will be passed down to the Query Loop Block's children.
	 * This can help, for example, to include additional settings or meta queries not
	 * directly supported by the core Query Loop Block, and extend its capabilities.
	 *
	 * Please note that this will only influence the query that will be rendered on the
	 * front-end. The editor preview is not affected by this filter. Also, worth noting
	 * that the editor preview uses the REST API, so, ideally, one should aim to provide
	 * attributes which are also compatible with the REST API, in order to be able to
	 * implement identical queries on both sides.
	 *
	 * @since 6.1.0
	 *
	 * @param array    $query Array containing parameters for `WP_Query` as parsed by the block context.
	 * @param WP_Block $block Block instance.
	 * @param int      $page  Current query's page.
	 */
	return apply_filters( 'query_loop_block_query_vars', $query, $block, $page );
}

/**
 * Helper function that returns the proper pagination arrow HTML for
 * `QueryPaginationNext` and `QueryPaginationPrevious` blocks based
 * on the provided `paginationArrow` from `QueryPagination` context.
 *
 * It's used in QueryPaginationNext and QueryPaginationPrevious blocks.
 *
 * @since 5.9.0
 *
 * @param WP_Block $block   Block instance.
 * @param bool     $is_next Flag for handling `next/previous` blocks.
 * @return string|null The pagination arrow HTML or null if there is none.
 */
function get_query_pagination_arrow( $block, $is_next ) {
	$arrow_map = array(
		'none'    => '',
		'arrow'   => array(
			'next'     => '→',
			'previous' => '←',
		),
		'chevron' => array(
			'next'     => '»',
			'previous' => '«',
		),
	);
	if ( ! empty( $block->context['paginationArrow'] ) && array_key_exists( $block->context['paginationArrow'], $arrow_map ) && ! empty( $arrow_map[ $block->context['paginationArrow'] ] ) ) {
		$pagination_type = $is_next ? 'next' : 'previous';
		$arrow_attribute = $block->context['paginationArrow'];
		$arrow           = $arrow_map[ $block->context['paginationArrow'] ][ $pagination_type ];
		$arrow_classes   = "wp-block-query-pagination-$pagination_type-arrow is-arrow-$arrow_attribute";
		return "<span class='$arrow_classes' aria-hidden='true'>$arrow</span>";
	}
	return null;
}

/**
 * Helper function that constructs a comment query vars array from the passed
 * block properties.
 *
 * It's used with the Comment Query Loop inner blocks.
 *
 * @since 6.0.0
 *
 * @param WP_Block $block Block instance.
 * @return array Returns the comment query parameters to use with the
 *               WP_Comment_Query constructor.
 */
function build_comment_query_vars_from_block( $block ) {

	$comment_args = array(
		'orderby'       => 'comment_date_gmt',
		'order'         => 'ASC',
		'status'        => 'approve',
		'no_found_rows' => false,
	);

	if ( is_user_logged_in() ) {
		$comment_args['include_unapproved'] = array( get_current_user_id() );
	} else {
		$unapproved_email = wp_get_unapproved_comment_author_email();

		if ( $unapproved_email ) {
			$comment_args['include_unapproved'] = array( $unapproved_email );
		}
	}

	if ( ! empty( $block->context['postId'] ) ) {
		$comment_args['post_id'] = (int) $block->context['postId'];
	}

	if ( get_option( 'thread_comments' ) ) {
		$comment_args['hierarchical'] = 'threaded';
	} else {
		$comment_args['hierarchical'] = false;
	}

	if ( get_option( 'page_comments' ) === '1' || get_option( 'page_comments' ) === true ) {
		$per_page     = get_option( 'comments_per_page' );
		$default_page = get_option( 'default_comments_page' );
		if ( $per_page > 0 ) {
			$comment_args['number'] = $per_page;

			$page = (int) get_query_var( 'cpage' );
			if ( $page ) {
				$comment_args['paged'] = $page;
			} elseif ( 'oldest' === $default_page ) {
				$comment_args['paged'] = 1;
			} elseif ( 'newest' === $default_page ) {
				$max_num_pages = (int) ( new WP_Comment_Query( $comment_args ) )->max_num_pages;
				if ( 0 !== $max_num_pages ) {
					$comment_args['paged'] = $max_num_pages;
				}
			}
			// Set the `cpage` query var to ensure the previous and next pagination links are correct
			// when inheriting the Discussion Settings.
			if ( 0 === $page && isset( $comment_args['paged'] ) && $comment_args['paged'] > 0 ) {
				set_query_var( 'cpage', $comment_args['paged'] );
			}
		}
	}

	return $comment_args;
}

/**
 * Helper function that returns the proper pagination arrow HTML for
 * `CommentsPaginationNext` and `CommentsPaginationPrevious` blocks based on the
 * provided `paginationArrow` from `CommentsPagination` context.
 *
 * It's used in CommentsPaginationNext and CommentsPaginationPrevious blocks.
 *
 * @since 6.0.0
 *
 * @param WP_Block $block           Block instance.
 * @param string   $pagination_type Optional. Type of the arrow we will be rendering.
 *                                  Accepts 'next' or 'previous'. Default 'next'.
 * @return string|null The pagination arrow HTML or null if there is none.
 */
function get_comments_pagination_arrow( $block, $pagination_type = 'next' ) {
	$arrow_map = array(
		'none'    => '',
		'arrow'   => array(
			'next'     => '→',
			'previous' => '←',
		),
		'chevron' => array(
			'next'     => '»',
			'previous' => '«',
		),
	);
	if ( ! empty( $block->context['comments/paginationArrow'] ) && ! empty( $arrow_map[ $block->context['comments/paginationArrow'] ][ $pagination_type ] ) ) {
		$arrow_attribute = $block->context['comments/paginationArrow'];
		$arrow           = $arrow_map[ $block->context['comments/paginationArrow'] ][ $pagination_type ];
		$arrow_classes   = "wp-block-comments-pagination-$pagination_type-arrow is-arrow-$arrow_attribute";
		return "<span class='$arrow_classes' aria-hidden='true'>$arrow</span>";
	}
	return null;
}