const { simpleParser } = require('mailparser');
const db = require('./db');
const emitter = require('./eventEmitter');
const { isRateLimited } = require('./rateLimiter');
const logger = require('./logger'); // 引入 logger

// Helper function to convert stream to buffer
function streamToBuffer(stream) {
    return new Promise((resolve, reject) => {
        const chunks = [];
        stream.on('data', (chunk) => chunks.push(chunk));
        stream.on('error', reject);
        stream.on('end', () => resolve(Buffer.concat(chunks)));
    });
}

async function saveEmail(stream) {
    try {
        // First, buffer the entire stream
        const emailBuffer = await streamToBuffer(stream);
        
        // Now, parse the buffered email content
        const parsed = await simpleParser(emailBuffer);

        const recipient = parsed.to ? parsed.to.text : 'undisclosed-recipients';
        const sender = parsed.from ? parsed.from.text : 'unknown-sender';
        //const rawEmail = emailBuffer.toString(); // 暂时去除 rawEmail，不在保存到数据库
        // 在这里进行速率限制检查
        if (isRateLimited(sender)) {
            // 记录被拒绝的事件
            logger.warn(`Email from <${sender}> rejected due to rate limiting.`, {
                sender: sender,
                recipient: recipient,
                action: 'rate-limit-reject'
            });
            // 如果被限流，则抛出错误，上游的SMTPServer会处理这个错误并拒绝邮件
            const error = new Error(`4.7.1 Domain of <${sender}> has been temporarily blocked due to rate limiting. Please try again later.`);
            error.responseCode = 421; // "Service not available, closing transmission channel"
            throw error;
        }

        const subject = parsed.subject || 'No Subject';
        const body = parsed.text || (parsed.html || '');

        // Manually create a timestamp for 'Asia/Shanghai' timezone
        const received_at = new Date().toLocaleString('sv-SE', {
            timeZone: 'Asia/Shanghai'
        });

        const [result] = await db.execute(
            'INSERT INTO emails (recipient, sender, subject, body, received_at) VALUES (?, ?, ?, ?, ?)',
            [recipient, sender, subject, body, received_at]
        );
        // const [result] = await db.execute(
        //     'INSERT INTO emails (recipient, sender, subject, body, raw) VALUES (?, ?, ?, ?, ?)',
        //     [recipient, sender, subject, body, rawEmail]
        // );
        const newEmailId = result.insertId;

        logger.info(`Email from <${sender}> to <${recipient}> saved with ID: ${newEmailId}`, {
            sender,
            recipient,
            subject,
            emailId: newEmailId,
            action: 'email-saved'
        });

        if (parsed.attachments && parsed.attachments.length > 0) {
            for (const attachment of parsed.attachments) {
                await db.execute(
                    'INSERT INTO email_attachments (email_id, filename, content_type, content) VALUES (?, ?, ?, ?)',
                    [newEmailId, attachment.filename, attachment.contentType, attachment.content]
                );
                logger.info(`Attachment ${attachment.filename} saved for email ID: ${newEmailId}`, {
                    filename: attachment.filename,
                    emailId: newEmailId,
                    action: 'attachment-saved'
                });
            }
        }

        // Emit an event with the new email's main information
        const [rows] = await db.execute('SELECT id, sender, recipient, subject, body, received_at FROM emails WHERE id = ?', [newEmailId]);
        if (rows.length > 0) {
            emitter.emit('newEmail', rows[0]);
            logger.info(`Event 'newEmail' emitted for email ID: ${newEmailId}`, {
                emailId: newEmailId,
                action: 'event-emitted'
            });
        }

    } catch (error) {
        // 如果错误是带有响应码的（例如我们的速率限制错误），它已经被记录过了。
        // 我们只记录其他意想不到的错误。
        if (!error.responseCode) {
            logger.error('Failed to save email due to an unexpected error:', {
                errorMessage: error.message,
                errorStack: error.stack
            });
        }
        // 重新抛出错误，以便上游的SMTPServer可以正确处理它。
        throw error;
    }
}

module.exports = { saveEmail };