<?php

/**

 * Server-side rendering of the `core/post-navigation-link` block.

 *

 * @package WordPress

 */

/**

 * Renders the `core/post-navigation-link` block on the server.

 *

 * @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 = isset( $attributes['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  = '';

	// 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'

				);

			}

		}

	}

	// The dynamic portion of the function name, `$navigation_type`,

	// refers to the type of adjacency, 'next' or 'previous'.

	$get_link_function = "get_{$navigation_type}_post_link";

	$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.

 */

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' );