<?php
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Reads and rewrites a theme's "Version:" header line (in style.css). See
 * FUFD_File_Rewriter for the shared file-rewrite mechanics also used by
 * FUFD_Version_Manager (plugins).
 */
class FUFD_Theme_Version_Manager {

	/**
	 * @param string $stylesheet Theme directory name (the "stylesheet" slug).
	 * @return string|WP_Error Current version as read from style.css.
	 */
	public static function get_current_version( $stylesheet ) {
		// Only ever touch a theme WordPress itself lists as installed.
		if ( ! array_key_exists( $stylesheet, wp_get_themes() ) ) {
			return new WP_Error( 'fufd_missing_theme', __( 'Theme not found.', 'downup' ) );
		}

		$theme = wp_get_theme( $stylesheet );

		$version = $theme->get( 'Version' );

		if ( empty( $version ) ) {
			return new WP_Error( 'fufd_missing_version', __( 'Theme has no Version header.', 'downup' ) );
		}

		return $version;
	}

	/**
	 * Rewrites the Version header in the theme's style.css only. WordPress's own
	 * update check then picks up the changed version.
	 *
	 * @param string $stylesheet
	 * @return true|WP_Error
	 */
	public static function prepare_fake_downgrade( $stylesheet ) {
		$current_version = self::get_current_version( $stylesheet );

		if ( is_wp_error( $current_version ) ) {
			return $current_version;
		}

		$fake_version = FUFD_File_Rewriter::compute_fake_version( $current_version );

		if ( is_wp_error( $fake_version ) ) {
			return $fake_version;
		}

		$theme = wp_get_theme( $stylesheet );
		$path  = $theme->get_stylesheet_directory() . '/style.css';

		$result = FUFD_File_Rewriter::rewrite_version_line( $path, $current_version, $fake_version );

		if ( is_wp_error( $result ) ) {
			return $result;
		}

		return true;
	}
}