<?php
/**
 * Server-side rendering of the `core/footnotes` block.
 *
 * @package WordPress
 */

/**
 * Renders the `core/footnotes` block on the server.
 *
 * @since 6.3.0
 *
 * @param array    $attributes Block attributes.
 * @param string   $content    Block default content.
 * @param WP_Block $block      Block instance.
 *
 * @return string Returns the HTML representing the footnotes.
 */
function render_block_core_footnotes( $attributes, $content, $block ) {
    // Bail out early if the post ID is not set for some reason.
    if ( empty( $block->context['postId'] ) ) {
        return '';
    }

    if ( post_password_required( $block->context['postId'] ) ) {
        return '';
    }

    $footnotes = get_post_meta( $block->context['postId'], 'footnotes', true );

    if ( ! $footnotes ) {
        return '';
    }

    $footnotes = json_decode( $footnotes, true );

    if ( ! is_array( $footnotes ) || count( $footnotes ) === 0 ) {
        return '';
    }

    $wrapper_attributes = get_block_wrapper_attributes();
    $footnote_index     = 1;

    $block_content = '';

    foreach ( $footnotes as $footnote ) {
        // Translators: %d: Integer representing the number of return links on the page.
        $aria_label     = sprintf( __( 'Jump to footnote reference %1$d' ), $footnote_index );
        $block_content .= sprintf(
            '<li id="%1$s">%2$s <a href="#%1$s-link" aria-label="%3$s">↩︎</a></li>',
            esc_attr( $footnote['id'] ),
            wp_kses_post( $footnote['content'] ),
            esc_attr( $aria_label )
        );
        ++$footnote_index;
    }

    return sprintf(
        '<ol %1$s>%2$s</ol>',
        $wrapper_attributes,
        $block_content
    );
}

/**
 * Registers the `core/footnotes` block on the server.
 *
 * @since 6.3.0
 */
function register_block_core_footnotes() {
    register_block_type_from_metadata(
        __DIR__ . '/footnotes',
        array(
            'render_callback' => 'render_block_core_footnotes',
        )
    );
}
add_action( 'init', 'register_block_core_footnotes' );


/**
 * Registers the footnotes meta field required for footnotes to work.
 *
 * @since 6.5.0
 */
function register_block_core_footnotes_post_meta() {
    $post_types = get_post_types( array( 'show_in_rest' => true ) );
    foreach ( $post_types as $post_type ) {
        // Only register the meta field if the post type supports the editor, custom fields, and revisions.
        if (
            post_type_supports( $post_type, 'editor' ) &&
            post_type_supports( $post_type, 'custom-fields' ) &&
            post_type_supports( $post_type, 'revisions' )
        ) {
            register_post_meta(
                $post_type,
                'footnotes',
                array(
                    'show_in_rest'      => true,
                    'single'            => true,
                    'type'              => 'string',
                    'revisions_enabled' => true,
                )
            );
        }
    }
}

/*
 * Most post types are registered at priority 10, so use priority 20 here in
 * order to catch them.
*/
add_action( 'init', 'register_block_core_footnotes_post_meta', 20 );

/**
 * Adds the footnotes field to the revisions display.
 *
 * @since 6.3.0
 *
 * @param array $fields The revision fields.
 * @return array The revision fields.
 */
function wp_add_footnotes_to_revision( $fields ) {
    $fields['footnotes'] = __( 'Footnotes' );
    return $fields;
}
add_filter( '_wp_post_revision_fields', 'wp_add_footnotes_to_revision' );

/**
 * Gets the footnotes field from the revision for the revisions screen.
 *
 * @since 6.3.0
 *
 * @param string $revision_field The field value, but $revision->$field
 *                               (footnotes) does not exist.
 * @param string $field          The field name, in this case "footnotes".
 * @param object $revision       The revision object to compare against.
 * @return string The field value.
 */
function wp_get_footnotes_from_revision( $revision_field, $field, $revision ) {
    return get_metadata( 'post', $revision->ID, $field, true );
}
add_filter( '_wp_post_revision_field_footnotes', 'wp_get_footnotes_from_revision', 10, 3 );