<?php
/**
 * POP3协议处理类
 */
require_once __DIR__ . '/../utils/Config.php';

class Pop3Handler {
    private $socket;
    private $clientIp;
    private $logger;
    private $config;
    private $state = 'auth'; // 状态：auth, transaction, update
    private $username = '';
    private $password = '';
    private $authenticated = false;
    private $messages = [];
    private $deletedMessages = [];
    private $messageCount = 0;
    private $mailboxSize = 0;
    
    /**
     * 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();
    }
    
    /**
     * 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)
        ]);
        
        // 按行处理数据
        $lines = explode("\r\n", $data);
        foreach ($lines as $line) {
            $line = trim($line);
            if (empty($line)) {
                continue;
            }
            
            $this->processCommand($line);
        }
    }
    
    /**
     * 处理POP3命令
     * @param string $command POP3命令
     */
    private function processCommand($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 'USER':
                $this->handleUser($params);
                break;
            case 'PASS':
                $this->handlePass($params);
                break;
            case 'STAT':
                $this->handleStat();
                break;
            case 'LIST':
                $this->handleList($params);
                break;
            case 'RETR':
                $this->handleRetr($params);
                break;
            case 'DELE':
                $this->handleDele($params);
                break;
            case 'NOOP':
                $this->handleNoop();
                break;
            case 'RSET':
                $this->handleRset();
                break;
            case 'QUIT':
                $this->handleQuit();
                break;
            case 'TOP':
                $this->handleTop($params);
                break;
            case 'UIDL':
                $this->handleUidl($params);
                break;
            default:
                $this->sendResponse(false, "Unknown command");
                break;
        }
    }
    
    /**
     * 处理USER命令
     * @param string $username 用户名
     */
    private function handleUser($username) {
        if ($this->state !== 'auth') {
            $this->sendResponse(false, "Bad sequence of commands");
            $this->logger->warning("USER command out of sequence from {ip}", [
                'ip' => $this->clientIp
            ]);
            return;
        }
        
        // 验证用户名格式
        if (empty($username) || strlen($username) > 50) {
            $this->sendResponse(false, "Invalid username");
            $this->logger->warning("Invalid username format from {ip}: {username}", [
                'ip' => $this->clientIp,
                'username' => $username
            ]);
            return;
        }
        
        $this->username = $username;
        $this->sendResponse(true, "User accepted");
        $this->logger->info("USER command received from {ip}, username: {username}", [
            'ip' => $this->clientIp,
            'username' => $this->username
        ]);
    }
    
    /**
     * 处理PASS命令
     * @param string $password 密码
     */
    private function handlePass($password) {
        if ($this->state !== 'auth' || empty($this->username)) {
            $this->sendResponse(false, "Bad sequence of commands");
            $this->logger->warning("PASS command out of sequence from {ip}", [
                'ip' => $this->clientIp
            ]);
            return;
        }
        
        $this->password = $password;
        
        try {
            // 调用数据库接口验证用户身份
            require_once __DIR__ . '/../utils/Database.php';
            $db = Database::getInstance();
            
            // 查询用户
            $sql = "SELECT * FROM user WHERE username = ? AND is_deleted = 0";
            $user = $db->query($sql, [$this->username])->fetch();
            
            if ($user && password_verify($password, $user['password'])) {
                $this->authenticated = true;
                $this->state = 'transaction';
                
                // 初始化邮件列表（从数据库获取）
                $this->initMessages($user['username']);
                
                $this->sendResponse(true, "Authentication successful");
                $this->logger->info("PASS command received from {ip}, authentication successful for user: {username}", [
                    'ip' => $this->clientIp,
                    'username' => $this->username
                ]);
            } else {
                $this->sendResponse(false, "Invalid username or password");
                $this->logger->warning("Authentication failed from {ip}, username: {username}", [
                    'ip' => $this->clientIp,
                    'username' => $this->username
                ]);
            }
        } catch (Exception $e) {
            $this->sendResponse(false, "Authentication error");
            $this->logger->error("Authentication exception from {ip}: {error}", [
                'ip' => $this->clientIp,
                'error' => $e->getMessage()
            ]);
        }
    }
    
    /**
     * 处理STAT命令
     */
    private function handleStat() {
        if (!$this->authenticated || $this->state !== 'transaction') {
            $this->sendResponse(false, "Not authenticated");
            return;
        }
        
        $this->sendResponse(true, "{$this->messageCount} {$this->mailboxSize}");
        $this->logger->info("STAT command received from {ip}", [
            'ip' => $this->clientIp
        ]);
    }
    
    /**
     * 处理LIST命令
     * @param string $messageId 邮件ID（可选）
     */
    private function handleList($messageId = '') {
        if (!$this->authenticated || $this->state !== 'transaction') {
            $this->sendResponse(false, "Not authenticated");
            return;
        }
        
        if (empty($messageId)) {
            // 列出所有邮件
            $response = "{$this->messageCount} messages\r\n";
            foreach ($this->messages as $id => $message) {
                $response .= "{$id} {$message['size']}\r\n";
            }
            $response .= ".\r\n";
            $this->sendRawResponse("+OK " . $response);
        } else {
            // 列出指定邮件
            $id = (int)$messageId;
            if (isset($this->messages[$id])) {
                $this->sendResponse(true, "{$id} {$this->messages[$id]['size']}");
            } else {
                $this->sendResponse(false, "No such message");
            }
        }
        
        $this->logger->info("LIST command received from {ip}, messageId: {messageId}", [
            'ip' => $this->clientIp,
            'messageId' => $messageId
        ]);
    }
    
    /**
     * 处理RETR命令
     * @param string $messageId 邮件ID
     */
    private function handleRetr($messageId) {
        if (!$this->authenticated || $this->state !== 'transaction') {
            $this->sendResponse(false, "Not authenticated");
            return;
        }
        
        $id = (int)$messageId;
        if (!isset($this->messages[$id])) {
            $this->sendResponse(false, "No such message");
            return;
        }
        
        $message = $this->messages[$id];
        $response = "{$message['size']} octets\r\n";
        $response .= $message['content'] . "\r\n";
        $response .= ".\r\n";
        $this->sendRawResponse("+OK " . $response);
        
        $this->logger->info("RETR command received from {ip}, messageId: {messageId}", [
            'ip' => $this->clientIp,
            'messageId' => $messageId
        ]);
    }
    
    /**
     * 处理DELE命令
     * @param string $messageId 邮件ID
     */
    private function handleDele($messageId) {
        if (!$this->authenticated || $this->state !== 'transaction') {
            $this->sendResponse(false, "Not authenticated");
            return;
        }
        
        $id = (int)$messageId;
        if (!isset($this->messages[$id])) {
            $this->sendResponse(false, "No such message");
            return;
        }
        
        $this->deletedMessages[$id] = true;
        $this->sendResponse(true, "Message {$id} marked for deletion");
        $this->logger->info("DELE command received from {ip}, messageId: {messageId}", [
            'ip' => $this->clientIp,
            'messageId' => $messageId
        ]);
    }
    
    /**
     * 处理NOOP命令
     */
    private function handleNoop() {
        if (!$this->authenticated) {
            $this->sendResponse(false, "Not authenticated");
            return;
        }
        
        $this->sendResponse(true, "OK");
        $this->logger->info("NOOP command received from {ip}", [
            'ip' => $this->clientIp
        ]);
    }
    
    /**
     * 处理RSET命令
     */
    private function handleRset() {
        if (!$this->authenticated || $this->state !== 'transaction') {
            $this->sendResponse(false, "Not authenticated");
            return;
        }
        
        $this->deletedMessages = [];
        $this->sendResponse(true, "Reset completed");
        $this->logger->info("RSET command received from {ip}", [
            'ip' => $this->clientIp
        ]);
    }
    
    /**
     * 处理QUIT命令
     */
    private function handleQuit() {
        $this->state = 'update';
        
        $deletedCount = 0;
        
        // 删除标记的邮件
        if (!empty($this->deletedMessages)) {
            try {
                require_once __DIR__ . '/../utils/Database.php';
                $db = Database::getInstance();
                
                $pdo = $db->beginTransaction();
                
                foreach ($this->deletedMessages as $id => $value) {
                    if (isset($this->messages[$id]) && isset($this->messages[$id]['email_id'])) {
                        $emailId = $this->messages[$id]['email_id'];
                        $sql = "DELETE FROM emails WHERE id = ?";
                        $db->execute($sql, [$emailId]);
                        $deletedCount++;
                    }
                }
                
                $db->commit($pdo);
            } catch (Exception $e) {
                $db->rollback($pdo);
                $this->logger->error("Failed to delete messages: {error}", [
                    'error' => $e->getMessage()
                ]);
            }
        }
        
        $this->sendResponse(true, "Bye");
        $this->logger->info("QUIT command received from {ip}, deleted {count} messages", [
            'ip' => $this->clientIp,
            'count' => $deletedCount
        ]);
        // 不再直接关闭socket，而是让Pop3Server通过检测连接关闭来处理
    }
    
    /**
     * 处理TOP命令
     * @param string $params 命令参数
     */
    private function handleTop($params) {
        if (!$this->authenticated || $this->state !== 'transaction') {
            $this->sendResponse(false, "Not authenticated");
            return;
        }
        
        $parts = explode(' ', $params);
        if (count($parts) !== 2) {
            $this->sendResponse(false, "Invalid parameters");
            return;
        }
        
        $id = (int)$parts[0];
        $lines = (int)$parts[1];
        
        if (!isset($this->messages[$id])) {
            $this->sendResponse(false, "No such message");
            return;
        }
        
        $message = $this->messages[$id];
        $headers = substr($message['content'], 0, strpos($message['content'], "\r\n\r\n"));
        $contentLines = explode("\r\n", substr($message['content'], strpos($message['content'], "\r\n\r\n") + 4));
        $topContent = implode("\r\n", array_slice($contentLines, 0, $lines));
        
        $response = "Top of message {$id}\r\n";
        $response .= $headers . "\r\n\r\n" . $topContent . "\r\n";
        $response .= ".\r\n";
        $this->sendRawResponse("+OK " . $response);
        
        $this->logger->info("TOP command received from {ip}, messageId: {id}, lines: {lines}", [
            'ip' => $this->clientIp,
            'id' => $id,
            'lines' => $lines
        ]);
    }
    
    /**
     * 处理UIDL命令
     * @param string $messageId 邮件ID（可选）
     */
    private function handleUidl($messageId = '') {
        if (!$this->authenticated || $this->state !== 'transaction') {
            $this->sendResponse(false, "Not authenticated");
            return;
        }
        
        if (empty($messageId)) {
            // 列出所有邮件的UID
            $response = "{$this->messageCount} messages\r\n";
            foreach ($this->messages as $id => $message) {
                $response .= "{$id} {$message['uid']}\r\n";
            }
            $response .= ".\r\n";
            $this->sendRawResponse("+OK " . $response);
        } else {
            // 列出指定邮件的UID
            $id = (int)$messageId;
            if (isset($this->messages[$id])) {
                $this->sendResponse(true, "{$id} {$this->messages[$id]['uid']}");
            } else {
                $this->sendResponse(false, "No such message");
            }
        }
        
        $this->logger->info("UIDL command received from {ip}, messageId: {messageId}", [
            'ip' => $this->clientIp,
            'messageId' => $messageId
        ]);
    }
    
    /**
     * 发送响应给客户端
     * @param bool $success 是否成功
     * @param string $message 响应消息
     */
    private function sendResponse($success, $message) {
        $prefix = $success ? "+OK" : "-ERR";
        $response = "$prefix $message\r\n";
        
        socket_write($this->socket, $response, strlen($response));
        
        $this->logger->debug("Sent response to {ip}: {response}", [
            'ip' => $this->clientIp,
            'response' => rtrim($response)
        ]);
    }
    
    /**
     * 发送原始响应给客户端
     * @param string $response 响应消息
     */
    private function sendRawResponse($response) {
        socket_write($this->socket, $response, strlen($response));
        
        $this->logger->debug("Sent raw response to {ip}: {response}", [
            'ip' => $this->clientIp,
            'response' => rtrim($response)
        ]);
    }
    
    /**
     * 初始化邮件列表（从数据库获取）
     * @param string $username 用户名
     */
    private function initMessages($username) {
        try {
            require_once __DIR__ . '/../utils/Database.php';
            $db = Database::getInstance();
            
            // 查询用户邮件
            $sql = "SELECT * FROM emails WHERE to_address = (SELECT email FROM user WHERE username = ? AND is_deleted = 0) ORDER BY send_time ASC";
            $emails = $db->query($sql, [$username])->fetchAll();
            
            $this->messages = [];
            $this->messageCount = 0;
            $this->mailboxSize = 0;
            $this->deletedMessages = [];
            
            if ($emails) {
                $id = 1;
                foreach ($emails as $email) {
                    // 构建完整的邮件内容
                    $content = "From: {$email['from_address']}\r\n" .
                               "To: {$email['to_address']}\r\n" .
                               "Subject: {$email['subject']}\r\n" .
                               "Date: {$email['created_at']}\r\n" .
                               "\r\n" .
                               "{$email['content']}\r\n";
                    
                    $this->messages[$id] = [
                        'uid' => $email['id'],
                        'size' => strlen($content),
                        'content' => $content,
                        'email_id' => $email['id'] // 保存数据库中的实际ID
                    ];
                    
                    $this->mailboxSize += $this->messages[$id]['size'];
                    $id++;
                }
            }
            
            $this->messageCount = count($this->messages);
            $this->logger->info("Loaded {count} emails for user {username}", [
                'count' => $this->messageCount,
                'username' => $this->username
            ]);
        } catch (Exception $e) {
            $this->messages = [];
            $this->messageCount = 0;
            $this->mailboxSize = 0;
            $this->deletedMessages = [];
            $this->logger->error("Failed to load messages for user {username}: {error}", [
                'username' => $this->username,
                'error' => $e->getMessage()
            ]);
        }
    }
}