<?php
/**
 * SMTP协议处理类
 */
require_once __DIR__ . '/../utils/Config.php';

class SmtpHandler {
    private $socket;
    private $clientIp;
    private $logger;
    private $config;
    private $state = 'init'; // 状态：init, helo, mail, rcpt, data, quit
    private $heloHost = '';
    private $fromAddress = '';
    private $toAddresses = [];
    private $dataBuffer = '';
    private $dataSize = 0;
    private $maxDataSize = 10 * 1024 * 1024; // 10MB
    
    /**
     * 构造函数
     * @param resource $socket 客户端socket
     * @param string $clientIp 客户端IP地址
     * @param Logger $logger 日志记录器
     */
    public function __construct($socket, $clientIp, $logger) {
        $this->socket = $socket;
        $this->clientIp = $clientIp;
        $this->logger = $logger;
        $this->config = Config::getInstance();
        $this->maxDataSize = $this->config->get('server.max_email_size', 10 * 1024 * 1024);
    }
    
    /**
     * 处理客户端数据
     * @param string $data 客户端发送的数据
     */
    public function handle($data) {
        $this->logger->debug("Received data from {ip}: {data}", [
            'ip' => $this->clientIp,
            'data' => rtrim($data)
        ]);
        
        // 如果处于数据状态，直接处理数据
        if ($this->state === 'data') {
            $this->handleDataContent($data);
        } else {
            // 按行处理命令
            $lines = explode("\r\n", $data);
            foreach ($lines as $line) {
                $line = trim($line);
                if (empty($line)) {
                    continue;
                }
                
                $this->processCommand($line);
            }
        }
    }
    
    /**
     * 处理SMTP命令
     * @param string $command SMTP命令
     */
    private function processCommand($command) {
        // 解析命令和参数
        $parts = preg_split('/\s+/', $command, 2);
        $cmd = strtoupper($parts[0]);
        $params = isset($parts[1]) ? $parts[1] : '';
        
        // 根据命令调用相应的处理方法
        switch ($cmd) {
            case 'HELO':
            case 'EHLO':
                $this->handleHelo($params);
                break;
            case 'MAIL':
                $this->handleMail($params);
                break;
            case 'RCPT':
                $this->handleRcpt($params);
                break;
            case 'DATA':
                $this->handleData();
                break;
            case 'RSET':
                $this->handleRset();
                break;
            case 'NOOP':
                $this->handleNoop();
                break;
            case 'QUIT':
                $this->handleQuit();
                break;
            default:
                $this->sendResponse(500, "500 Syntax error, command unrecognized");
                break;
        }
    }
    
    /**
     * 处理HELO/EHLO命令
     * @param string $params 命令参数
     */
    private function handleHelo($params) {
        $this->heloHost = $params;
        $this->state = 'helo';
        $this->sendResponse(250, "250 {domain} Hello {host} [{ip}]");
        $this->logger->info("HELO/EHLO command received from {ip}, host: {host}", [
            'ip' => $this->clientIp,
            'host' => $this->heloHost
        ]);
    }
    
    /**
     * 处理MAIL FROM命令
     * @param string $params 命令参数
     */
    private function handleMail($params) {
        if ($this->state !== 'helo') {
            $this->sendResponse(503, "503 Bad sequence of commands");
            $this->logger->warning("MAIL FROM command out of sequence from {ip}", [
                'ip' => $this->clientIp
            ]);
            return;
        }
        
        // 解析发件人地址
        preg_match('/^FROM:\s*<([^>]*)>/i', $params, $matches);
        if (empty($matches)) {
            $this->sendResponse(501, "501 Syntax error in parameters or arguments");
            $this->logger->warning("Invalid MAIL FROM syntax from {ip}: {params}", [
                'ip' => $this->clientIp,
                'params' => $params
            ]);
            return;
        }
        
        $sender = $matches[1];
        
        // 验证发件人邮箱格式
        if (!filter_var($sender, FILTER_VALIDATE_EMAIL)) {
            $this->sendResponse(553, "553 5.1.8 Invalid sender email address");
            $this->logger->warning("Invalid sender email from {ip}: {sender}", [
                'ip' => $this->clientIp,
                'sender' => $sender
            ]);
            return;
        }
        
        $this->fromAddress = $sender;
        $this->state = 'mail';
        $this->toAddresses = [];
        $this->sendResponse(250, "250 2.1.0 Sender OK");
        $this->logger->info("MAIL FROM command received from {ip}, from: {from}", [
            'ip' => $this->clientIp,
            'from' => $this->fromAddress
        ]);
    }
    
    /**
     * 处理RCPT TO命令
     * @param string $params 命令参数
     */
    private function handleRcpt($params) {
        if ($this->state !== 'mail') {
            $this->sendResponse(503, "503 Bad sequence of commands");
            $this->logger->warning("RCPT TO command out of sequence from {ip}", [
                'ip' => $this->clientIp
            ]);
            return;
        }
        
        // 解析收件人地址
        preg_match('/^TO:\s*<([^>]*)>/i', $params, $matches);
        if (empty($matches)) {
            $this->sendResponse(501, "501 Syntax error in parameters or arguments");
            $this->logger->warning("Invalid RCPT TO syntax from {ip}: {params}", [
                'ip' => $this->clientIp,
                'params' => $params
            ]);
            return;
        }
        
        $toAddress = $matches[1];
        
        // 验证收件人邮箱格式
        if (!filter_var($toAddress, FILTER_VALIDATE_EMAIL)) {
            $this->sendResponse(553, "553 5.1.8 Invalid recipient email address");
            $this->logger->warning("Invalid recipient email from {ip}: {to}", [
                'ip' => $this->clientIp,
                'to' => $toAddress
            ]);
            return;
        }
        
        // 检查收件人数量是否超过限制
        if (count($this->toAddresses) >= 100) {
            $this->sendResponse(452, "452 4.5.3 Too many recipients");
            $this->logger->warning("Too many recipients from {ip}", [
                'ip' => $this->clientIp
            ]);
            return;
        }
        
        $this->toAddresses[] = $toAddress;
        $this->sendResponse(250, "250 2.1.5 Recipient OK");
        $this->logger->info("RCPT TO command received from {ip}, to: {to}", [
            'ip' => $this->clientIp,
            'to' => $toAddress
        ]);
    }
    
    /**
     * 处理DATA命令
     */
    private function handleData() {
        if ($this->state !== 'mail' || empty($this->toAddresses)) {
            $this->sendResponse(503, "503 Bad sequence of commands");
            return;
        }
        
        $this->state = 'data';
        $this->dataBuffer = '';
        $this->dataSize = 0;
        $this->sendResponse(354, "354 Start mail input; end with <CRLF>.<CRLF>");
        $this->logger->info("DATA command received from {ip}", [
            'ip' => $this->clientIp
        ]);
    }
    
    /**
     * 处理RSET命令
     */
    private function handleRset() {
        $this->state = 'helo';
        $this->fromAddress = '';
        $this->toAddresses = [];
        $this->dataBuffer = '';
        $this->dataSize = 0;
        $this->sendResponse(250, "250 2.0.0 OK");
        $this->logger->info("RSET command received from {ip}", [
            'ip' => $this->clientIp
        ]);
    }
    
    /**
     * 处理NOOP命令
     */
    private function handleNoop() {
        $this->sendResponse(250, "250 2.0.0 OK");
        $this->logger->info("NOOP command received from {ip}", [
            'ip' => $this->clientIp
        ]);
    }
    
    /**
     * 处理DATA内容
     * @param string $data 邮件内容
     */
    private function handleDataContent($data) {
        // 添加到缓冲区
        $this->dataBuffer .= $data;
        $this->dataSize += strlen($data);
        
        // 检查数据大小是否超过限制
        if ($this->dataSize > $this->maxDataSize) {
            $this->sendResponse(552, "552 5.2.3 Message exceeds maximum size");
            $this->state = 'helo';
            $this->dataBuffer = '';
            $this->dataSize = 0;
            $this->logger->warning("Message from {ip} exceeds maximum size", [
                'ip' => $this->clientIp
            ]);
            return;
        }
        
        // 检查是否收到结束标记
        if (substr($this->dataBuffer, -5) === "\r\n.\r\n") {
            // 去除结束标记
            $emailContent = substr($this->dataBuffer, 0, -5);
            
            // 处理邮件
            $this->processEmail($emailContent);
            
            // 重置状态
            $this->state = 'helo';
            $this->dataBuffer = '';
            $this->dataSize = 0;
        }
    }
    
    /**
     * 处理并保存邮件
     * @param string $emailContent 邮件内容
     */
    private function processEmail($emailContent) {
        // 解析邮件头
        $headers = $this->parseEmailHeaders($emailContent);
        
        // 提取邮件主题和正文
        $subject = $headers['Subject'] ?? '无主题';
        $body = $this->extractEmailBody($emailContent);
        
        // 保存邮件到数据库
        $this->saveEmailToDatabase($headers, $subject, $body);
        
        // 发送成功响应
        $this->sendResponse(250, "250 2.0.0 OK: queued as {message_id}");
        
        $this->logger->info("Email from {from} to {to} saved successfully", [
            'from' => $this->fromAddress,
            'to' => implode(', ', $this->toAddresses)
        ]);
    }
    
    /**
     * 解析邮件头
     * @param string $emailContent 邮件内容
     * @return array 邮件头
     */
    private function parseEmailHeaders($emailContent) {
        $headers = [];
        $lines = explode("\r\n", $emailContent);
        
        // 解析邮件头
        foreach ($lines as $line) {
            if (empty($line)) {
                break; // 邮件头结束
            }
            
            // 处理多行邮件头
            if (preg_match('/^\s+/', $line)) {
                // 多行邮件头，追加到上一个头
                $lastHeader = array_key_last($headers);
                $headers[$lastHeader] .= ' ' . trim($line);
            } else {
                // 新的邮件头
                $parts = explode(':', $line, 2);
                if (count($parts) === 2) {
                    $name = trim($parts[0]);
                    $value = trim($parts[1]);
                    $headers[$name] = $value;
                }
            }
        }
        
        return $headers;
    }
    
    /**
     * 提取邮件正文
     * @param string $emailContent 邮件内容
     * @return string 邮件正文
     */
    private function extractEmailBody($emailContent) {
        $parts = explode("\r\n\r\n", $emailContent, 2);
        return isset($parts[1]) ? $parts[1] : '';
    }
    
    /**
     * 保存邮件到数据库
     * @param array $headers 邮件头
     * @param string $subject 邮件主题
     * @param string $body 邮件正文
     */
    private function saveEmailToDatabase($headers, $subject, $body) {
        try {
            // 包含数据库类
            require_once __DIR__ . '/../utils/Database.php';
            
            // 连接数据库
            $db = Database::getInstance();
            
            // 遍历收件人地址
            foreach ($this->toAddresses as $toAddress) {
                // 根据收件人邮箱查找对应的用户名
            $sql = "SELECT username FROM user WHERE email = ? AND is_deleted = 0";
            $user = $db->fetchOne($sql, [$toAddress]);
            $userId = $user ? $user['username'] : 'admin'; // 如果找不到，使用默认用户名（admin为管理员）
                
                // 保存邮件
                $sql = "INSERT INTO emails (from_address, to_address, subject, content, user_id, send_time) VALUES (?, ?, ?, ?, ?, NOW())";
                $db->insert($sql, [
                    $this->fromAddress,
                    $toAddress,
                    $subject,
                    $body,
                    $userId
                ]);
            }
        } catch (Exception $e) {
            $this->logger->error("Failed to save email: {error}", [
                'error' => $e->getMessage()
            ]);
        }
    }
    
    /**
     * 处理QUIT命令
     */
    private function handleQuit() {
        $this->sendResponse(221, "221 2.0.0 Bye");
        $this->logger->info("QUIT command received from {ip}", [
            'ip' => $this->clientIp
        ]);
        // 不再直接关闭socket，而是让SmtpServer通过检测连接关闭来处理
    }
    
    /**
     * 发送响应给客户端
     * @param int $code 响应代码
     * @param string $message 响应消息
     */
    private function sendResponse($code, $message) {
        // 替换占位符
        $domain = $this->config->get('server.domain', 'test.com');
        $message = str_replace('{domain}', $domain, $message);
        $message = str_replace('{ip}', $this->clientIp, $message);
        $message = str_replace('{host}', $this->heloHost, $message);
        
        // 添加换行符
        $response = $message . "\r\n";
        
        // 发送响应
        socket_write($this->socket, $response, strlen($response));
        
        $this->logger->debug("Sent response to {ip}: {response}", [
            'ip' => $this->clientIp,
            'response' => rtrim($response)
        ]);
    }
}