<?php
/**
 * Custom CSS block support.
 *
 * @package WordPress
 */

/**
 * Render the custom CSS stylesheet and add class name to block as required.
 *
 * @since 7.0.0
 *
 * @param array $parsed_block The parsed block.
 * @return array The same parsed block with custom CSS class name added if appropriate.
 *
 * @phpstan-param array{
 *     blockName: string|null,
 *     attrs: array{
 *         className?: string,
 *         style?: array{
 *             css?: string,
 *             ...
 *         },
 *         ...
 *     },
 *     ...
 * } $parsed_block
 */
function wp_render_custom_css_support_styles( $parsed_block ) {
    $custom_css = $parsed_block['attrs']['style']['css'] ?? null;
    if ( ! is_string( $custom_css ) || '' === trim( $custom_css ) ) {
        return $parsed_block;
    }

    $block_type = WP_Block_Type_Registry::get_instance()->get_registered( $parsed_block['blockName'] );
    if ( ! block_has_support( $block_type, 'customCSS', true ) ) {
        return $parsed_block;
    }

    // Validate CSS doesn't contain HTML markup (same validation as global styles REST API).
    if ( preg_match( '#</?\w+#', $custom_css ) ) {
        return $parsed_block;
    }

    // Generate a unique class name for this block instance.
    $class_name          = wp_unique_id_from_values( $parsed_block, 'wp-custom-css-' );
    $existing_class_name = $parsed_block['attrs']['className'] ?? null;
    $updated_class_name  = is_string( $existing_class_name )
        ? "$existing_class_name $class_name"
        : $class_name;

    _wp_array_set( $parsed_block, array( 'attrs', 'className' ), $updated_class_name );

    // Process the custom CSS using the same method as global styles.
    $selector      = '.' . $class_name;
    $processed_css = WP_Theme_JSON::process_blocks_custom_css( $custom_css, $selector );

    if ( ! empty( $processed_css ) ) {
        /*
         * Register and add inline style for block custom CSS.
         * The style depends on global-styles to ensure custom CSS loads after
         * and can override global styles.
         */
        wp_register_style( 'wp-block-custom-css', false, array( 'global-styles' ) );
        wp_add_inline_style( 'wp-block-custom-css', $processed_css );
    }

    return $parsed_block;
}

/**
 * Enqueues the block custom CSS styles.
 *
 * @since 7.0.0
 */
function wp_enqueue_block_custom_css() {
    wp_enqueue_style( 'wp-block-custom-css' );
}

/**
 * Applies the custom CSS class name to the block's rendered HTML.
 *
 * The class name is generated in {@see wp_render_custom_css_support_styles()}
 * and stored in block attributes. This filter adds it to the actual markup.
 *
 * @since 7.0.0
 *
 * @param string $block_content Rendered block content.
 * @param array  $block         Block object.
 * @return string               Filtered block content.
 *
 * @phpstan-param array{
 *     attrs: array{
 *         className?: string,
 *         ...
 *     },
 *     ...
 * } $block
 */
function wp_render_custom_css_class_name( $block_content, $block ) {
    $class_name_attr = $block['attrs']['className'] ?? null;

    if ( ! is_string( $class_name_attr ) || ! str_contains( $class_name_attr, 'wp-custom-css-' ) ) {
        return $block_content;
    }

    // Parse out the 'wp-custom-css-*' class name added by wp_render_custom_css_support_styles().
    $custom_class_name = null;
    $token_delimiter   = " \t\f\r\n";
    $class_token       = strtok( $class_name_attr, $token_delimiter );
    while ( false !== $class_token ) {
        if ( str_starts_with( $class_token, 'wp-custom-css-' ) ) {
            $custom_class_name = $class_token;
            break;
        }
        $class_token = strtok( $token_delimiter );
    }
    if ( null === $custom_class_name ) {
        return $block_content;
    }

    $tags = new WP_HTML_Tag_Processor( $block_content );

    if ( $tags->next_tag() ) {
        $tags->add_class( 'has-custom-css' );
        $tags->add_class( $custom_class_name );
    }

    return $tags->get_updated_html();
}

add_filter( 'render_block', 'wp_render_custom_css_class_name', 10, 2 );
add_filter( 'render_block_data', 'wp_render_custom_css_support_styles', 10, 1 );
add_action( 'wp_enqueue_scripts', 'wp_enqueue_block_custom_css', 1 );

/**
 * Registers the style block attribute for block types that support it.
 *
 * @param WP_Block_Type $block_type Block Type.
 */
function wp_register_custom_css_support( $block_type ) {
    // Setup attributes and styles within that if needed.
    if ( ! $block_type->attributes ) {
        $block_type->attributes = array();
    }

    // Check for existing style attribute definition e.g. from block.json.
    if ( array_key_exists( 'style', $block_type->attributes ) ) {
        return;
    }

    $has_custom_css_support = block_has_support( $block_type, array( 'customCSS' ), true );

    if ( $has_custom_css_support ) {
        $block_type->attributes['style'] = array(
            'type' => 'object',
        );
    }
}

/**
 * Strips custom CSS (`style.css` in attributes) from all blocks in post content.
 *
 * Uses {@see WP_Block_Parser::next_token()} to scan block tokens and surgically
 * replace only the attribute JSON that changed — no parse_blocks() +
 * serialize_blocks() round-trip needed.
 *
 * @since 7.0.0
 * @access private
 *
 * @param string $content Post content to filter, expected to be escaped with slashes.
 * @return string Filtered post content with block custom CSS removed.
 */
function wp_strip_custom_css_from_blocks( $content ) {
    if ( ! has_blocks( $content ) ) {
        return $content;
    }

    $unslashed = stripslashes( $content );

    $parser           = new WP_Block_Parser();
    $parser->document = $unslashed;
    $parser->offset   = 0;
    $end              = strlen( $unslashed );
    $replacements     = array();

    while ( $parser->offset < $end ) {
        $next_token = $parser->next_token();

        if ( 'no-more-tokens' === $next_token[0] ) {
            break;
        }

        list( $token_type, , $attrs, $start_offset, $token_length ) = $next_token;

        $parser->offset = $start_offset + $token_length;

        if ( 'block-opener' !== $token_type && 'void-block' !== $token_type ) {
            continue;
        }

        if ( ! isset( $attrs['style']['css'] ) ) {
            continue;
        }

        // Remove css and clean up empty style.
        unset( $attrs['style']['css'] );
        if ( empty( $attrs['style'] ) ) {
            unset( $attrs['style'] );
        }

        // Locate the JSON portion within the token.
        $token_string   = substr( $unslashed, $start_offset, $token_length );
        $json_rel_start = strcspn( $token_string, '{' );
        $json_rel_end   = strrpos( $token_string, '}' );

        $json_start  = $start_offset + $json_rel_start;
        $json_length = $json_rel_end - $json_rel_start + 1;

        // Re-encode attributes. If attrs is now empty, remove JSON and trailing space.
        if ( empty( $attrs ) ) {
            // Remove the trailing space after JSON.
            $replacements[] = array( $json_start, $json_length + 1, '' );
        } else {
            $replacements[] = array( $json_start, $json_length, serialize_block_attributes( $attrs ) );
        }
    }

    if ( empty( $replacements ) ) {
        return $content;
    }

    // Build the result by splicing replacements into the original string.
    $result = '';
    $was_at = 0;

    foreach ( $replacements as $replacement ) {
        list( $offset, $length, $new_json ) = $replacement;
        $result                            .= substr( $unslashed, $was_at, $offset - $was_at ) . $new_json;
        $was_at                             = $offset + $length;
    }

    if ( $was_at < $end ) {
        $result .= substr( $unslashed, $was_at );
    }

    return addslashes( $result );
}

/**
 * Adds the filters to strip custom CSS from block content on save.
 * Priority of 8 to run before wp_filter_global_styles_post (priority 9) and wp_filter_post_kses (priority 10).
 *
 * @since 7.0.0
 * @access private
 */
function wp_custom_css_kses_init_filters() {
    add_filter( 'content_save_pre', 'wp_strip_custom_css_from_blocks', 8 );
    add_filter( 'content_filtered_save_pre', 'wp_strip_custom_css_from_blocks', 8 );
}

/**
 * Removes the filters that strip custom CSS from block content on save.
 * Priority of 8 to run before wp_filter_global_styles_post (priority 9) and wp_filter_post_kses (priority 10).
 *
 * @since 7.0.0
 * @access private
 */
function wp_custom_css_remove_filters() {
    remove_filter( 'content_save_pre', 'wp_strip_custom_css_from_blocks', 8 );
    remove_filter( 'content_filtered_save_pre', 'wp_strip_custom_css_from_blocks', 8 );
}

/**
 * Registers the custom CSS content filters if the user does not have the edit_css capability.
 *
 * @since 7.0.0
 * @access private
 */
function wp_custom_css_kses_init() {
    wp_custom_css_remove_filters();
    if ( ! current_user_can( 'edit_css' ) ) {
        wp_custom_css_kses_init_filters();
    }
}

/**
 * Initializes custom CSS content filters when imported data should be filtered.
 *
 * Runs at priority 999 on {@see 'force_filtered_html_on_import'} to ensure it
 * fires after general KSES initialization, independently of user capabilities.
 * If the input of the filter is true it means we are in an import situation and should
 * enable the custom CSS filters, independently of the user capabilities.
 *
 * @since 7.0.0
 * @access private
 *
 * @param mixed $arg Input argument of the filter.
 * @return mixed Input argument of the filter.
 */
function wp_custom_css_force_filtered_html_on_import_filter( $arg ) {
    if ( $arg ) {
        wp_custom_css_kses_init_filters();
    }
    return $arg;
}

// Run before wp_filter_global_styles_post (priority 9) and wp_filter_post_kses (priority 10).
add_action( 'init', 'wp_custom_css_kses_init', 20 );
add_action( 'set_current_user', 'wp_custom_css_kses_init' );
add_filter( 'force_filtered_html_on_import', 'wp_custom_css_force_filtered_html_on_import_filter', 999 );

// Register the block support.
WP_Block_Supports::get_instance()->register(
    'custom-css',
    array(
        'register_attribute' => 'wp_register_custom_css_support',
    )
);