<?php
/**
 * 文件备份接收端API - 同步版本
 * 支持按目录固定ID，MD5变化覆盖备份
 * 兼容 PHP 5.3 - PHP 8.2
 */

// 错误报告设置
error_reporting(E_ALL & ~E_NOTICE & ~E_STRICT & ~E_DEPRECATED);
ini_set('display_errors', 0);
ini_set('max_execution_time', 300);
ini_set('memory_limit', '256M');

class FileBackupReceiver {
    private $backupBaseDir = 'backup_storage';
    private $chunkDir = 'chunks';
    private $maxFileSize = 209715200; // 200MB限制
    private $historyFile = 'backup_history.json';
    
    public function __construct($baseDir = null) {
        if ($baseDir) {
            $this->backupBaseDir = $baseDir;
        }
        
        // 创建必要的目录
        $this->createDirectory($this->backupBaseDir);
        $this->createDirectory($this->backupBaseDir . '/' . $this->chunkDir);
    }
    
    /**
     * 创建目录
     */
    private function createDirectory($dir) {
        if (!file_exists($dir)) {
            mkdir($dir, 0755, true);
        }
    }
    
    /**
     * 处理API请求
     */
    public function handleRequest() {
        $action = isset($_POST['action']) ? $_POST['action'] : 
                  (isset($_GET['action']) ? $_GET['action'] : '');
        $backupId = isset($_POST['backup_id']) ? $_POST['backup_id'] : 
                    (isset($_GET['backup_id']) ? $_GET['backup_id'] : '');
        
        // 验证备份ID
        if (empty($backupId) && $action != 'test') {
            return $this->jsonResponse(['success' => false, 'error' => '无效的备份ID']);
        }
        
        switch ($action) {
            case 'upload':
                return $this->uploadFile($backupId);
                
            case 'upload_chunk':
                return $this->uploadChunk($backupId);
                
            case 'merge_chunks':
                return $this->mergeChunks($backupId);
                
            case 'check_md5':
                return $this->checkFileMd5($backupId);
                
            case 'test':
                return $this->testConnection();
                
            default:
                return $this->jsonResponse(['success' => false, 'error' => '无效的操作']);
        }
    }
    
    /**
     * 检查文件MD5，决定是否需要覆盖
     */
    private function checkFileMd5($backupId) {
        $filePath = isset($_POST['file_path']) ? $_POST['file_path'] : '';
        $fileMd5 = isset($_POST['file_md5']) ? $_POST['file_md5'] : '';
        
        if (empty($filePath) || empty($fileMd5)) {
            return $this->jsonResponse(['success' => false, 'error' => '缺少参数']);
        }
        
        $savePath = $this->getSavePath($backupId, $filePath);
        
        // 检查文件是否存在
        if (!file_exists($savePath)) {
            return $this->jsonResponse([
                'success' => true,
                'need_upload' => true,
                'reason' => '文件不存在'
            ]);
        }
        
        // 检查MD5是否匹配
        $existingMd5 = md5_file($savePath);
        if ($existingMd5 !== $fileMd5) {
            return $this->jsonResponse([
                'success' => true,
                'need_upload' => true,
                'reason' => 'MD5不匹配',
                'existing_md5' => $existingMd5,
                'new_md5' => $fileMd5
            ]);
        }
        
        // 文件已存在且MD5匹配，无需上传
        return $this->jsonResponse([
            'success' => true,
            'need_upload' => false,
            'reason' => '文件已存在且MD5相同',
            'file_size' => filesize($savePath)
        ]);
    }
    
    /**
     * 上传单个文件（支持覆盖）
     */
    private function uploadFile($backupId) {
        $filePath = isset($_POST['file_path']) ? $_POST['file_path'] : '';
        $fileContent = isset($_POST['file_content']) ? $_POST['file_content'] : '';
        $fileMd5 = isset($_POST['file_md5']) ? $_POST['file_md5'] : '';
        $fileSize = isset($_POST['file_size']) ? intval($_POST['file_size']) : 0;
        
        if (empty($filePath) || empty($fileContent)) {
            return $this->jsonResponse(['success' => false, 'error' => '缺少文件数据']);
        }
        
        // 验证文件大小
        if ($fileSize > $this->maxFileSize) {
            return $this->jsonResponse(['success' => false, 'error' => '文件大小超过限制']);
        }
        
        // 解码文件内容
        $content = base64_decode($fileContent);
        if ($content === false) {
            return $this->jsonResponse(['success' => false, 'error' => '文件解码失败']);
        }
        
        // 验证MD5
        $receivedMd5 = md5($content);
        if ($fileMd5 && $receivedMd5 !== $fileMd5) {
            return $this->jsonResponse(['success' => false, 'error' => '文件校验失败']);
        }
        
        // 检查是否需要覆盖
        $savePath = $this->getSavePath($backupId, $filePath);
        $needOverwrite = false;
        
        if (file_exists($savePath)) {
            $existingMd5 = md5_file($savePath);
            if ($existingMd5 === $fileMd5) {
                // MD5相同，跳过上传
                return $this->jsonResponse([
                    'success' => true,
                    'message' => '文件已存在且MD5相同，跳过上传',
                    'skipped' => true,
                    'path' => $savePath
                ]);
            }
            $needOverwrite = true;
        }
        
        // 保存文件
        $this->createDirectory(dirname($savePath));
        
        if (file_put_contents($savePath, $content) !== false) {
            // 记录备份信息
            $this->logBackup($backupId, $filePath, $fileSize, $fileMd5, $needOverwrite);
            return $this->jsonResponse([
                'success' => true,
                'message' => $needOverwrite ? '文件覆盖成功' : '文件上传成功',
                'path' => $savePath,
                'overwritten' => $needOverwrite
            ]);
        } else {
            return $this->jsonResponse(['success' => false, 'error' => '文件保存失败']);
        }
    }
    
    /**
     * 上传分块
     */
    private function uploadChunk($backupId) {
        $filePath = isset($_POST['file_path']) ? $_POST['file_path'] : '';
        $chunkIndex = isset($_POST['chunk_index']) ? intval($_POST['chunk_index']) : 0;
        $totalChunks = isset($_POST['total_chunks']) ? intval($_POST['total_chunks']) : 0;
        $chunkData = isset($_POST['chunk_data']) ? $_POST['chunk_data'] : '';
        $chunkSize = isset($_POST['chunk_size']) ? intval($_POST['chunk_size']) : 0;
        
        if (empty($filePath) || empty($chunkData) || $totalChunks == 0) {
            return $this->jsonResponse(['success' => false, 'error' => '缺少分块数据']);
        }
        
        // 解码分块数据
        $content = base64_decode($chunkData);
        if ($content === false) {
            return $this->jsonResponse(['success' => false, 'error' => '分块解码失败']);
        }
        
        // 验证分块大小
        if (strlen($content) != $chunkSize) {
            return $this->jsonResponse(['success' => false, 'error' => '分块大小不匹配']);
        }
        
        // 保存分块
        $chunkFileName = $this->getChunkFileName($backupId, $filePath, $chunkIndex);
        if (file_put_contents($chunkFileName, $content) !== false) {
            return $this->jsonResponse([
                'success' => true,
                'message' => '分块上传成功',
                'chunk_index' => $chunkIndex
            ]);
        } else {
            return $this->jsonResponse(['success' => false, 'error' => '分块保存失败']);
        }
    }
    
    /**
     * 合并分块（支持覆盖）
     */
    private function mergeChunks($backupId) {
        $filePath = isset($_POST['file_path']) ? $_POST['file_path'] : '';
        $totalChunks = isset($_POST['total_chunks']) ? intval($_POST['total_chunks']) : 0;
        $fileMd5 = isset($_POST['file_md5']) ? $_POST['file_md5'] : '';
        $fileSize = isset($_POST['file_size']) ? intval($_POST['file_size']) : 0;
        
        if (empty($filePath) || $totalChunks == 0) {
            return $this->jsonResponse(['success' => false, 'error' => '缺少合并参数']);
        }
        
        // 验证文件大小
        if ($fileSize > $this->maxFileSize) {
            return $this->jsonResponse(['success' => false, 'error' => '文件大小超过限制']);
        }
        
        // 检查是否需要覆盖
        $savePath = $this->getSavePath($backupId, $filePath);
        $needOverwrite = false;
        
        if (file_exists($savePath)) {
            $existingMd5 = md5_file($savePath);
            if ($existingMd5 === $fileMd5) {
                // MD5相同，跳过合并，删除分块文件
                $this->cleanupChunks($backupId, $filePath, $totalChunks);
                return $this->jsonResponse([
                    'success' => true,
                    'message' => '文件已存在且MD5相同，跳过合并',
                    'skipped' => true,
                    'path' => $savePath
                ]);
            }
            $needOverwrite = true;
        }
        
        // 合并所有分块
        $this->createDirectory(dirname($savePath));
        
        $fp = fopen($savePath, 'wb');
        if (!$fp) {
            return $this->jsonResponse(['success' => false, 'error' => '创建文件失败']);
        }
        
        $success = true;
        for ($i = 0; $i < $totalChunks; $i++) {
            $chunkFileName = $this->getChunkFileName($backupId, $filePath, $i);
            if (!file_exists($chunkFileName)) {
                $success = false;
                break;
            }
            
            $chunkData = file_get_contents($chunkFileName);
            if ($chunkData === false) {
                $success = false;
                break;
            }
            
            fwrite($fp, $chunkData);
            
            // 删除分块文件
            unlink($chunkFileName);
        }
        
        fclose($fp);
        
        if (!$success) {
            @unlink($savePath);
            return $this->jsonResponse(['success' => false, 'error' => '合并分块失败']);
        }
        
        // 验证合并后的文件
        if ($fileMd5) {
            $actualMd5 = md5_file($savePath);
            if ($actualMd5 !== $fileMd5) {
                @unlink($savePath);
                return $this->jsonResponse(['success' => false, 'error' => '文件校验失败']);
            }
        }
        
        // 验证文件大小
        $actualSize = filesize($savePath);
        if ($actualSize != $fileSize) {
            @unlink($savePath);
            return $this->jsonResponse(['success' => false, 'error' => '文件大小不匹配']);
        }
        
        // 记录备份信息
        $this->logBackup($backupId, $filePath, $fileSize, $fileMd5, $needOverwrite);
        
        return $this->jsonResponse([
            'success' => true,
            'message' => $needOverwrite ? '文件覆盖合并成功' : '文件合并成功',
            'path' => $savePath,
            'overwritten' => $needOverwrite
        ]);
    }
    
    /**
     * 清理分块文件
     */
    private function cleanupChunks($backupId, $filePath, $totalChunks) {
        for ($i = 0; $i < $totalChunks; $i++) {
            $chunkFileName = $this->getChunkFileName($backupId, $filePath, $i);
            if (file_exists($chunkFileName)) {
                @unlink($chunkFileName);
            }
        }
    }
    
    /**
     * 获取分块文件名
     */
    private function getChunkFileName($backupId, $filePath, $chunkIndex) {
        $safePath = md5($filePath);
        return $this->backupBaseDir . '/' . $this->chunkDir . '/' . 
               $backupId . '_' . $safePath . '_' . $chunkIndex . '.chunk';
    }
    
    /**
     * 获取保存路径
     */
    private function getSavePath($backupId, $filePath) {
        // 创建备份ID目录（基于目录的固定ID）
        $backupDir = $this->backupBaseDir . '/' . $backupId;
        $this->createDirectory($backupDir);
        
        return $backupDir . '/' . $filePath;
    }
    
    /**
     * 记录备份信息
     */
    private function logBackup($backupId, $filePath, $fileSize, $fileMd5, $overwritten = false) {
        $logFile = $this->backupBaseDir . '/' . $backupId . '/backup_log.json';
        
        $logData = [];
        if (file_exists($logFile)) {
            $content = file_get_contents($logFile);
            $logData = json_decode($content, true);
            if (!is_array($logData)) {
                $logData = [];
            }
        }
        
        $logData[$filePath] = [
            'size' => $fileSize,
            'md5' => $fileMd5,
            'backup_time' => date('Y-m-d H:i:s'),
            'timestamp' => time(),
            'overwritten' => $overwritten
        ];
        
        file_put_contents($logFile, json_encode($logData, JSON_PRETTY_PRINT));
        
        // 同时更新主备份历史
        $this->updateBackupHistory($backupId, $filePath, $fileSize, $overwritten);
    }
    
    /**
     * 更新备份历史
     */
    private function updateBackupHistory($backupId, $filePath, $fileSize, $overwritten = false) {
        $history = [];
        if (file_exists($this->historyFile)) {
            $content = file_get_contents($this->historyFile);
            $history = json_decode($content, true);
            if (!is_array($history)) {
                $history = [];
            }
        }
        
        if (!isset($history[$backupId])) {
            $history[$backupId] = [
                'first_backup' => date('Y-m-d H:i:s'),
                'last_backup' => date('Y-m-d H:i:s'),
                'files' => [],
                'total_size' => 0,
                'total_files' => 0,
                'overwritten_count' => 0
            ];
        }
        
        // 如果是覆盖操作且文件已存在，更新统计
        $existingSize = 0;
        if ($overwritten && isset($history[$backupId]['files'][$filePath])) {
            $existingSize = $history[$backupId]['files'][$filePath]['size'];
            $history[$backupId]['overwritten_count']++;
        }
        
        $history[$backupId]['files'][$filePath] = [
            'size' => $fileSize,
            'backup_time' => date('Y-m-d H:i:s'),
            'overwritten' => $overwritten
        ];
        
        // 更新总大小（减去被覆盖文件的大小）
        $history[$backupId]['total_size'] = $history[$backupId]['total_size'] - $existingSize + $fileSize;
        $history[$backupId]['total_files'] = count($history[$backupId]['files']);
        $history[$backupId]['last_backup'] = date('Y-m-d H:i:s');
        
        file_put_contents($this->historyFile, json_encode($history, JSON_PRETTY_PRINT));
    }
    
    /**
     * 测试连接
     */
    private function testConnection() {
        return $this->jsonResponse([
            'success' => true,
            'message' => 'API连接正常',
            'server_time' => date('Y-m-d H:i:s'),
            'php_version' => PHP_VERSION,
            'storage_path' => realpath($this->backupBaseDir),
            'max_file_size' => $this->formatSize($this->maxFileSize)
        ]);
    }
    
    /**
     * 格式化文件大小
     */
    private function formatSize($bytes) {
        $units = ['B', 'KB', 'MB', 'GB', 'TB'];
        $i = 0;
        while ($bytes >= 1024 && $i < count($units) - 1) {
            $bytes /= 1024;
            $i++;
        }
        return round($bytes, 2) . ' ' . $units[$i];
    }
    
    /**
     * JSON响应
     */
    private function jsonResponse($data) {
        header('Content-Type: application/json; charset=utf-8');
        echo json_encode($data);
        exit;
    }
}

// 处理请求
$receiver = new FileBackupReceiver();
$receiver->handleRequest();
?>