<?php

/**
 * @package     MokoSuiteBackup
 * @subpackage  com_mokosuitebackup
 * @author      Moko Consulting <hello@mokoconsulting.tech>
 * @copyright   Copyright (C) 2026 Moko Consulting. All rights reserved.
 * @license     GNU General Public License version 3 or later; see LICENSE
 *
 * Differential file scanner — compares current filesystem against a
 * stored manifest from the last full backup. Only returns files that
 * are new or modified since the base backup.
 *
 * Manifest format (JSON):
 *   {"path/to/file": {"size": 1234, "mtime": 1717350000}, ...}
 */

namespace Joomla\Component\MokoSuiteBackup\Administrator\Engine;

defined('_JEXEC') or die;

class DifferentialScanner
{
	/**
	 * Build a file manifest for the current state of the site.
	 *
	 * @param   string[]  $filePaths  Array of relative file paths (from FileScanner)
	 * @param   string    $rootDir    Joomla root directory
	 *
	 * @return  array<string, array{size: int, mtime: int}>
	 */
	public static function buildManifest(array $filePaths, string $rootDir): array
	{
		$manifest = [];

		foreach ($filePaths as $relativePath) {
			$fullPath = rtrim($rootDir, '/') . '/' . $relativePath;

			if (!is_file($fullPath)) {
				continue;
			}

			$manifest[$relativePath] = [
				'size'  => (int) filesize($fullPath),
				'mtime' => (int) filemtime($fullPath),
			];
		}

		return $manifest;
	}

	/**
	 * Compare current files against a base manifest and return only changed/new files.
	 *
	 * @param   array   $currentFiles   Array of relative file paths from FileScanner
	 * @param   array   $baseManifest   Manifest from the base full backup
	 * @param   string  $rootDir        Joomla root directory
	 *
	 * @return  string[]  Array of relative paths that are new or modified
	 */
	public static function getChangedFiles(array $currentFiles, array $baseManifest, string $rootDir): array
	{
		$changed = [];

		foreach ($currentFiles as $relativePath) {
			$fullPath = rtrim($rootDir, '/') . '/' . $relativePath;

			if (!is_file($fullPath)) {
				continue;
			}

			// New file — not in base manifest
			if (!isset($baseManifest[$relativePath])) {
				$changed[] = $relativePath;

				continue;
			}

			// Check if modified (size or mtime changed)
			$currentSize  = (int) filesize($fullPath);
			$currentMtime = (int) filemtime($fullPath);
			$baseEntry    = $baseManifest[$relativePath];

			if ($currentSize !== $baseEntry['size'] || $currentMtime !== $baseEntry['mtime']) {
				$changed[] = $relativePath;
			}
		}

		return $changed;
	}
}