<?php

/**

 * Theme previews using the Site Editor for block themes.

 *

 * @package WordPress

 */

/**

 * Filters the blog option to return the path for the previewed theme.

 *

 * @since 6.3.0

 *

 * @param string $current_stylesheet The current theme's stylesheet or template path.

 * @return string The previewed theme's stylesheet or template path.

 */

function wp_get_theme_preview_path( $current_stylesheet = null ) {

	if ( ! current_user_can( 'switch_themes' ) ) {

		return $current_stylesheet;

	}

	$preview_stylesheet = ! empty( $_GET['wp_theme_preview'] ) ? sanitize_text_field( wp_unslash( $_GET['wp_theme_preview'] ) ) : null;

	$wp_theme           = wp_get_theme( $preview_stylesheet );

	if ( ! is_wp_error( $wp_theme->errors() ) ) {

		if ( current_filter() === 'template' ) {

			$theme_path = $wp_theme->get_template();

		} else {

			$theme_path = $wp_theme->get_stylesheet();

		}

		return sanitize_text_field( $theme_path );

	}

	return $current_stylesheet;

}

/**

 * Adds a middleware to `apiFetch` to set the theme for the preview.

 * This adds a `wp_theme_preview` URL parameter to API requests from the Site Editor, so they also respond as if the theme is set to the value of the parameter.

 *

 * @since 6.3.0

 */

function wp_attach_theme_preview_middleware() {

	// Don't allow non-admins to preview themes.

	if ( ! current_user_can( 'switch_themes' ) ) {

		return;

	}

	wp_add_inline_script(

		'wp-api-fetch',

		sprintf(

			'wp.apiFetch.use( wp.apiFetch.createThemePreviewMiddleware( %s ) );',

			wp_json_encode( sanitize_text_field( wp_unslash( $_GET['wp_theme_preview'] ) ) )

		),

		'after'

	);

}

/**

 * Set a JavaScript constant for theme activation.

 *

 * Sets the JavaScript global WP_BLOCK_THEME_ACTIVATE_NONCE containing the nonce

 * required to activate a theme. For use within the site editor.

 *

 * @see https://github.com/WordPress/gutenberg/pull/41836

 *

 * @since 6.3.0

 * @access private

 */

function wp_block_theme_activate_nonce() {

	$nonce_handle = 'switch-theme_' . wp_get_theme_preview_path();

	?>

	<script type="text/javascript">

		window.WP_BLOCK_THEME_ACTIVATE_NONCE = <?php echo wp_json_encode( wp_create_nonce( $nonce_handle ) ); ?>;

	</script>

	<?php

}

/**

 * Add filters and actions to enable Block Theme Previews in the Site Editor.

 *

 * The filters and actions should be added after `pluggable.php` is included as they may

 * trigger code that uses `current_user_can()` which requires functionality from `pluggable.php`.

 *

 * @since 6.3.2

 */

function wp_initialize_theme_preview_hooks() {

	if ( ! empty( $_GET['wp_theme_preview'] ) ) {

		add_filter( 'stylesheet', 'wp_get_theme_preview_path' );

		add_filter( 'template', 'wp_get_theme_preview_path' );

		add_action( 'init', 'wp_attach_theme_preview_middleware' );

		add_action( 'admin_head', 'wp_block_theme_activate_nonce' );

	}

}