<?php
declare(strict_types=1);

namespace WP_Rocket\Engine\Plugin;

use WP_Rocket\Admin\Options_Data;

class OptionsBackup {

	/**
	 * Number of backup files to keep.
	 *
	 * @var int
	 */
	const KEEP_COUNT = 4;

	/**
	 * Path to the wp-rocket-config/ directory.
	 *
	 * @var string
	 */
	private $config_path;

	/**
	 * Plugin options.
	 *
	 * @var Options_Data
	 */
	private $options;

	/**
	 * Constructor.
	 *
	 * @param string       $config_path Absolute path to the config directory (trailing slash).
	 * @param Options_Data $options     Plugin options instance.
	 */
	public function __construct( string $config_path, Options_Data $options ) {
		$this->config_path = $config_path;
		$this->options     = $options;
	}

	/**
	 * Backs up the current options before a plugin upgrade runs.
	 *
	 * Skips if the upgrade is a rollback (new < old) or if a backup for
	 * $old_version already exists (only the first snapshot per version is kept).
	 *
	 * @param string $new_version Incoming plugin version.
	 * @param string $old_version Currently installed plugin version.
	 * @return bool True when a backup was written, false when skipped or failed.
	 */
	public function backup( string $new_version, string $old_version ): bool {
		if ( version_compare( $new_version, $old_version, '<' ) ) {
			return false;
		}

		if ( $this->backup_exists_for_version( $old_version ) ) {
			return false;
		}

		$options = $this->options->get_options();

		if ( empty( $options ) ) {
			return false;
		}

		rocket_init_config_dir();

		$filename = 'wp_rocket_settings_backup_' . $old_version . '_' . gmdate( 'Y-m-d-H-i-s' ) . '.json';
		$written  = rocket_put_content(
			$this->config_path . $filename,
			(string) wp_json_encode( $options, JSON_PRETTY_PRINT )
		);

		if ( ! $written ) {
			return false;
		}

		$this->garbage_collect();

		return true;
	}

	/**
	 * Checks whether a backup file for the given version already exists.
	 *
	 * @param string $version Plugin version to look up.
	 * @return bool
	 */
	private function backup_exists_for_version( string $version ): bool {
		$files = glob( $this->config_path . 'wp_rocket_settings_backup_' . $version . '_*.json' );
		return ! empty( $files );
	}

	/**
	 * Deletes oldest backup files beyond KEEP_COUNT, sorted by modification time.
	 */
	private function garbage_collect(): void {
		$files = glob( $this->config_path . 'wp_rocket_settings_backup_*.json' );

		if ( ! $files || count( $files ) <= self::KEEP_COUNT ) {
			return;
		}

		usort(
			$files,
			function ( string $a, string $b ): int {
				return filemtime( $b ) - filemtime( $a );
			}
		);

		$filesystem = rocket_direct_filesystem();

		foreach ( array_slice( $files, self::KEEP_COUNT ) as $old_file ) {
			$filesystem->delete( $old_file );
		}
	}
}