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

/**
 * Renders the `core/post-navigation-link` block on the server.
 *
 * @since 5.9.0
 *
 * @param array  $attributes Block attributes.
 * @param string $content    Block default content.
 *
 * @return string Returns the next or previous post link that is adjacent to the current post.
 */
function render_block_core_post_navigation_link( $attributes, $content ) {
    if ( ! is_singular() ) {
        return '';
    }

    // Get the navigation type to show the proper link. Available options are `next|previous`.
    $navigation_type = $attributes['type'] ?? 'next';
    // Allow only `next` and `previous` in `$navigation_type`.
    if ( ! in_array( $navigation_type, array( 'next', 'previous' ), true ) ) {
        return '';
    }
    $classes = "post-navigation-link-$navigation_type";
    if ( isset( $attributes['textAlign'] ) ) {
        $classes .= " has-text-align-{$attributes['textAlign']}";
    }
    $wrapper_attributes = get_block_wrapper_attributes(
        array(
            'class' => $classes,
        )
    );
    // Set default values.
    $format = '%link';
    $link   = 'next' === $navigation_type ? _x( 'Next', 'label for next post link' ) : _x( 'Previous', 'label for previous post link' );
    $label  = '';

    // Only use hardcoded values here, otherwise we need to add escaping where these values are used.
    $arrow_map = array(
        'none'    => '',
        'arrow'   => array(
            'next'     => '→',
            'previous' => '←',
        ),
        'chevron' => array(
            'next'     => '»',
            'previous' => '«',
        ),
    );

    // If a custom label is provided, make this a link.
    // `$label` is used to prepend the provided label, if we want to show the page title as well.
    if ( isset( $attributes['label'] ) && ! empty( $attributes['label'] ) ) {
        $label = "{$attributes['label']}";
        $link  = $label;
    }

    // If we want to also show the page title, make the page title a link and prepend the label.
    if ( isset( $attributes['showTitle'] ) && $attributes['showTitle'] ) {
        /*
         * If the label link option is not enabled but there is a custom label,
         * display the custom label as text before the linked title.
         */
        if ( ! $attributes['linkLabel'] ) {
            if ( $label ) {
                $format = '<span class="post-navigation-link__label">' . wp_kses_post( $label ) . '</span> %link';
            }
            $link = '%title';
        } elseif ( isset( $attributes['linkLabel'] ) && $attributes['linkLabel'] ) {
            // If the label link option is enabled and there is a custom label, display it before the title.
            if ( $label ) {
                $link = '<span class="post-navigation-link__label">' . wp_kses_post( $label ) . '</span> <span class="post-navigation-link__title">%title</span>';
            } else {
                /*
                 * If the label link option is enabled and there is no custom label,
                 * add a colon between the label and the post title.
                 */
                $label = 'next' === $navigation_type ? _x( 'Next:', 'label before the title of the next post' ) : _x( 'Previous:', 'label before the title of the previous post' );
                $link  = sprintf(
                    '<span class="post-navigation-link__label">%1$s</span> <span class="post-navigation-link__title">%2$s</span>',
                    wp_kses_post( $label ),
                    '%title'
                );
            }
        }
    }

    // Display arrows.
    if ( isset( $attributes['arrow'] ) && 'none' !== $attributes['arrow'] && isset( $arrow_map[ $attributes['arrow'] ] ) ) {
        $arrow = $arrow_map[ $attributes['arrow'] ][ $navigation_type ];

        if ( 'next' === $navigation_type ) {
            $format = '%link<span class="wp-block-post-navigation-link__arrow-next is-arrow-' . $attributes['arrow'] . '" aria-hidden="true">' . $arrow . '</span>';
        } else {
            $format = '<span class="wp-block-post-navigation-link__arrow-previous is-arrow-' . $attributes['arrow'] . '" aria-hidden="true">' . $arrow . '</span>%link';
        }
    }

    /*
     * The dynamic portion of the function name, `$navigation_type`,
     * Refers to the type of adjacency, 'next' or 'previous'.
     *
     * @see https://developer.wordpress.org/reference/functions/get_previous_post_link/
     * @see https://developer.wordpress.org/reference/functions/get_next_post_link/
     */
    $get_link_function = "get_{$navigation_type}_post_link";

    if ( ! empty( $attributes['taxonomy'] ) ) {
        $content = $get_link_function( $format, $link, true, '', $attributes['taxonomy'] );
    } else {
        $content = $get_link_function( $format, $link );
    }

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

/**
 * Registers the `core/post-navigation-link` block on the server.
 *
 * @since 5.9.0
 */
function register_block_core_post_navigation_link() {
    register_block_type_from_metadata(
        __DIR__ . '/post-navigation-link',
        array(
            'render_callback' => 'render_block_core_post_navigation_link',
        )
    );
}
add_action( 'init', 'register_block_core_post_navigation_link' );