<?php
/**
 * Determine and compare MD5 checksums with PHP
 * 
 * @author	Helmut Kaczmarek <email@helmutkaczmarek.de>
 * @link	https://wiki.helmutkaczmarek.de/code:php:checksum
 */

// Allowed file extensions
$allowedExtensions = array('jpg', 'jpeg', 'dng', 'cr2');

// Directory containing the files to be examined
$dataDirectory = 'D:\Folder';
 
// Directory containing this script
$scriptDirectory = 'D:\Folder\Checksum';

// Folder name for checksum files (will be subfolder of $scriptDirectory)
$listsDirectory = $scriptDirectory . '\Lists';

// Folder name for log files (will be subfolder of $scriptDirectory)
$logsDirectory = $scriptDirectory . '\Logs';

// Number of checksum files and log files to be kept
$filesToKeep = 10;

// Timezone (otherwise $currentTimestamp will use UTC)
date_default_timezone_set('Europe/Berlin');

// Generate the current timestamp in format YYYYMMDD_HHMMSS
$currentTimestamp = date('Ymd_His');

// Check if the subfolders exist, otherwise create them
if (!is_dir($listsDirectory)) {
    mkdir($listsDirectory);
}
if (!is_dir($logsDirectory)) {
    mkdir($logsDirectory);
}

// File name for the checksum file and log file including time stamp
$checksumFilename = $listsDirectory . '\\' . $currentTimestamp . '_checksum.txt';
$logFilename = $logsDirectory . '\\' . $currentTimestamp . '_log.txt';

// Function to search directories recursively
function scanDirectory($directory) {
    global $allowedExtensions, $checksumFilename;
    
    $files = scandir($directory);
    
    foreach ($files as $file) {
        if ($file !== '.' && $file !== '..') {
            $filePath = $directory . '\\' . $file;
            
            if (is_dir($filePath)) {
                scanDirectory($filePath);
            } else {
                $extension = strtolower(pathinfo($file, PATHINFO_EXTENSION));
                
                if (in_array($extension, $allowedExtensions)) {
                    $md5Checksum = md5_file($filePath);
                    
                    // Write the MD5 checksum to the checksum file
                    file_put_contents($checksumFilename, "$md5Checksum\t$filePath\n", FILE_APPEND);
                    
                    // Display the current filename on the command prompt
                    echo "Processing $filePath\n";
                }
            }
        }
    }
}

// Search the directory recursively for files
scanDirectory($dataDirectory);

// Write log file
$logEntry = "MD5 checksums have been created and stored in $checksumFilename.\n";
file_put_contents($logFilename, $logEntry, FILE_APPEND);

// Function to delete old files
function deleteOldFiles($directory) {
    global $filesToKeep;
    
    $allFiles = glob($directory . '\*.*');
    
    // Use array_multisort() to sort by modification time in descending order
    array_multisort(array_map('filemtime', $allFiles), SORT_DESC, $allFiles);

    // Only keep the last $filesToKeep
    $filesToKeepArray = array_slice($allFiles, 0, $filesToKeep);
    foreach ($allFiles as $file) {
        if (!in_array($file, $filesToKeepArray)) {
            unlink($file);
        }
    }
}

// Delete old checksum files and log files
deleteOldFiles($listsDirectory);
deleteOldFiles($logsDirectory);

// Checksum file comparison function
function compareChecksumFiles($file1, $file2) {
    $checksums1 = file($file1, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    $checksums2 = file($file2, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    
    $differentFiles = array();

    foreach ($checksums1 as $line1) {
        list($checksum1, $file1) = explode("\t", $line1);
        foreach ($checksums2 as $line2) {
            list($checksum2, $file2) = explode("\t", $line2);
            if ($file1 === $file2 && $checksum1 !== $checksum2) {
                $differentFiles[] = $file1;
                break;
            }
        }
    }
    
    return $differentFiles;
}

// Paths to the last two checksum files
$lastChecksumFiles = glob($listsDirectory . '\*_checksum.txt', GLOB_NOSORT);
if (count($lastChecksumFiles) >= 2) {
    $lastChecksumFile1 = $lastChecksumFiles[count($lastChecksumFiles) - 1];
    $lastChecksumFile2 = $lastChecksumFiles[count($lastChecksumFiles) - 2];

    $differentFiles = compareChecksumFiles($lastChecksumFile1, $lastChecksumFile2);

    // Output and log file
    $logMessage = '';

    if (count($differentFiles) > 0) {
        echo "ATTENTION: Different MD5 checksums found! See log file in $logFilename.\n";
        $logMessage .= "ATTENTION: The following files have different checksums:\n";
        foreach ($differentFiles as $file) {
            $logMessage .= "$file\n";
        }
    } else {
        $logMessage .= "INFO: No different MD5 checksums found.\n";
        echo "INFO: No different MD5 checksums found.\n";
    }

    file_put_contents($logFilename, $logMessage, FILE_APPEND);
}

echo $logEntry;
?>