/**
 * @file        邮件发送服务类
 * @author      hotok
 * @date        2025-06-29
 * @lastEditor  hotok
 * @lastEditTime 2025-06-29
 * @description 提供邮件发送、模板邮件、健康检查等功能，支持重试机制和错误处理
 */

import nodemailer from 'nodemailer';
import { smtpConfig, emailConfig, emailTemplates, emailOptions } from '@/config/email.config';
import { Logger } from '@/plugins/logger/logger.service';
import type {
    EmailTransporter,
    EmailSendOptions,
    EmailTemplateSendOptions,
    EmailSendResult,
    EmailServiceStatus,
    EmailHealthCheckResult,
    EmailTemplateType,
    EmailTemplateParams,
} from '@/type/email.type';

/**
 * 邮件发送服务类
 * 使用单例模式管理邮件发送功能
 */
export class EmailService {
    /** 单例实例 */
    private static instance: EmailService | null = null;

    /** 邮件传输器实例 */
    private _transporter: EmailTransporter | null = null;

    /** 服务状态信息 */
    private _status: EmailServiceStatus;

    /** 初始化标志 */
    private _isInitialized = false;

    /**
     * 私有构造函数，防止外部实例化
     */
    private constructor() {
        this._status = {
            status: 'unhealthy',
            transporterStatus: 'disconnected',
            error: undefined,
            lastCheckAt: new Date(),
        };
    }

    /**
     * 获取单例实例
     */
    public static getInstance(): EmailService {
        if (!EmailService.instance) {
            EmailService.instance = new EmailService();
        }
        return EmailService.instance;
    }

    /**
     * 获取邮件传输器实例
     */
    public get transporter(): EmailTransporter {
        if (!this._transporter) {
            throw new Error('邮件服务未初始化，请先调用 initialize() 方法');
        }
        return this._transporter;
    }

    /**
     * 获取服务状态信息
     */
    public get status(): EmailServiceStatus {
        return { ...this._status };
    }

    /**
     * 检查是否已初始化
     */
    public get isInitialized(): boolean {
        return this._isInitialized;
    }

    /**
     * 验证邮件配置
     */
    private validateConfig(): void {
        if (!smtpConfig.host || !smtpConfig.port) {
            throw new Error('SMTP配置无效：缺少host或port');
        }

        if (!smtpConfig.auth.user || !smtpConfig.auth.pass) {
            throw new Error('SMTP配置无效：缺少用户名或密码');
        }

        if (smtpConfig.port < 1 || smtpConfig.port > 65535) {
            throw new Error(`SMTP端口号无效: ${smtpConfig.port}`);
        }
    }

    /**
     * 更新服务状态
     */
    private updateStatus(
        status: EmailServiceStatus['status'],
        transporterStatus: EmailServiceStatus['transporterStatus'],
        error?: string
    ): void {
        this._status = {
            status,
            transporterStatus,
            error,
            lastCheckAt: new Date(),
        };
    }

    /**
     * 初始化邮件服务
     */
    public async initialize(): Promise<EmailTransporter> {
        // 防止重复初始化
        if (this._isInitialized && this._transporter) {
            Logger.debug('邮件服务已初始化，返回现有实例');
            return this._transporter;
        }

        try {
            this.validateConfig();
            this.updateStatus('unhealthy', 'disconnected');

            // 创建邮件传输器
            this._transporter = nodemailer.createTransport({
                host: smtpConfig.host,
                port: smtpConfig.port,
                secure: smtpConfig.secure,
                auth: {
                    user: smtpConfig.auth.user,
                    pass: smtpConfig.auth.pass,
                },
                connectionTimeout: smtpConfig.connectionTimeout,
                greetingTimeout: smtpConfig.greetingTimeout,
                socketTimeout: smtpConfig.socketTimeout,
                pool: true, // 使用连接池
                maxConnections: 5, // 最大连接数
                maxMessages: 100, // 每个连接最大消息数
            });

            // 验证SMTP连接
            await this._transporter.verify();

            this._isInitialized = true;
            this.updateStatus('healthy', 'connected');

            Logger.debug({
                message: '邮件服务初始化成功',
                host: smtpConfig.host,
                port: smtpConfig.port,
                secure: smtpConfig.secure,
                user: smtpConfig.auth.user,
            });

            return this._transporter;
        } catch (error) {
            const errorMessage = error instanceof Error ? error.message : String(error);
            this.updateStatus('unhealthy', 'error', errorMessage);
            Logger.error(new Error(`邮件服务初始化失败: ${errorMessage}`));
            throw new Error(`邮件服务初始化失败: ${errorMessage}`);
        }
    }

    /**
     * 发送邮件
     */
    public async sendEmail(options: EmailSendOptions): Promise<EmailSendResult> {
        const startTime = Date.now();
        let retryCount = 0;

        while (retryCount <= emailOptions.retryAttempts) {
            try {
                if (!this._transporter) {
                    throw new Error('邮件传输器未初始化');
                }

                // 准备邮件选项 - 确保From字段格式正确
                const fromAddress = options.from || emailConfig.from;
                if (!fromAddress) {
                    throw new Error('发件人邮箱地址不能为空，请检查SMTP_USER或SMTP_FROM_EMAIL环境变量');
                }
                
                const fromName = emailConfig.fromName || '星撰系统';
                const formattedFrom = fromAddress.includes('<') 
                    ? fromAddress 
                    : `"${fromName}" <${fromAddress}>`;

                const mailOptions = {
                    from: formattedFrom,
                    to: Array.isArray(options.to) ? options.to.join(', ') : options.to,
                    cc: options.cc ? (Array.isArray(options.cc) ? options.cc.join(', ') : options.cc) : undefined,
                    bcc: options.bcc ? (Array.isArray(options.bcc) ? options.bcc.join(', ') : options.bcc) : undefined,
                    subject: options.subject,
                    text: options.text,
                    html: options.html,
                    replyTo: options.replyTo || emailConfig.replyTo,
                    priority: options.priority || emailConfig.priority,
                    attachments: options.attachments,
                    headers: options.headers,
                    messageId: options.messageId,
                    references: options.references,
                    inReplyTo: options.inReplyTo,
                };

                // 发送邮件
                const result = await this._transporter.sendMail(mailOptions);

                const sendResult: EmailSendResult = {
                    success: true,
                    messageId: result.messageId,
                    accepted: result.accepted || [],
                    rejected: result.rejected || [],
                    pending: result.pending || [],
                    response: result.response,
                    sentAt: new Date(),
                    retryCount,
                };

                Logger.debug({
                    message: '邮件发送成功',
                    messageId: result.messageId,
                    to: options.to,
                    subject: options.subject,
                    responseTime: Date.now() - startTime,
                    retryCount,
                });

                return sendResult;
            } catch (error) {
                retryCount++;
                const errorMessage = error instanceof Error ? error.message : String(error);

                Logger.warn({
                    message: '邮件发送失败',
                    error: errorMessage,
                    to: options.to,
                    subject: options.subject,
                    retryCount,
                    maxRetries: emailOptions.retryAttempts,
                });

                // 如果已达到最大重试次数，返回失败结果
                if (retryCount > emailOptions.retryAttempts) {
                    return {
                        success: false,
                        accepted: [],
                        rejected: Array.isArray(options.to) ? options.to : [options.to],
                        pending: [],
                        error: errorMessage,
                        sentAt: new Date(),
                        retryCount: retryCount - 1,
                    };
                }

                // 等待重试延迟
                await new Promise(resolve => setTimeout(resolve, emailOptions.retryDelay));
            }
        }

        // 这个分支理论上不会执行，但为了类型安全
        return {
            success: false,
            accepted: [],
            rejected: Array.isArray(options.to) ? options.to : [options.to],
            pending: [],
            error: '未知错误',
            sentAt: new Date(),
            retryCount: emailOptions.retryAttempts,
        };
    }

    /**
     * 发送模板邮件
     */
    public async sendTemplateEmail(options: EmailTemplateSendOptions): Promise<EmailSendResult> {
        try {
            const template = emailTemplates[options.template];
            if (!template) {
                throw new Error(`未找到邮件模板: ${options.template}`);
            }

            // 渲染邮件内容
            const { subject, html, text } = this.renderTemplate(options.template, options.params);

            // 构建发送选项
            const sendOptions: EmailSendOptions = {
                to: options.to,
                cc: options.cc,
                bcc: options.bcc,
                subject: options.subject || subject,
                html,
                text,
                priority: options.priority,
                attachments: options.attachments,
            };

            return await this.sendEmail(sendOptions);
        } catch (error) {
            const errorMessage = error instanceof Error ? error.message : String(error);
            Logger.error(new Error(`模板邮件发送失败: ${errorMessage}`));

            return {
                success: false,
                accepted: [],
                rejected: Array.isArray(options.to) ? options.to : [options.to],
                pending: [],
                error: errorMessage,
                sentAt: new Date(),
                retryCount: 0,
            };
        }
    }

    /**
     * 渲染邮件模板
     */
    private renderTemplate(
        templateType: EmailTemplateType,
        params: EmailTemplateParams
    ): { subject: string; html: string; text: string } {
        const template = emailTemplates[templateType];
        const defaultParams = {
            systemName: '星撰系统',
            companyName: '星撰科技',
            supportEmail: smtpConfig.auth.user,
            ...params,
        };

        let subject = template.subject;
        let html = '';
        let text = '';

        switch (templateType) {
            case 'activation':
                subject = template.subject;
                html = this.getActivationTemplate(defaultParams);
                text = `您好 ${defaultParams.nickname || defaultParams.username}，\n\n请点击以下链接激活您的账户：\n${defaultParams.activationUrl}\n\n或使用激活码：${defaultParams.activationCode}\n\n链接将在 ${defaultParams.expireTime} 后过期。\n\n如果您没有注册账户，请忽略此邮件。\n\n${defaultParams.systemName}`;
                break;

            case 'passwordReset':
                subject = emailTemplates.passwordReset.subject;
                html = this.getPasswordResetTemplate(defaultParams);
                text = `您好 ${defaultParams.nickname || defaultParams.username}，\n\n我们收到了重置您账户密码的请求。请点击以下链接重置密码：\n${defaultParams.resetUrl}\n\n或使用重置码：${defaultParams.resetCode}\n\n链接将在 ${defaultParams.expireTime} 后过期。\n\n如果您没有请求重置密码，请忽略此邮件。\n\n${defaultParams.systemName}`;
                break;

            case 'welcome':
                subject = template.subject;
                html = this.getWelcomeTemplate(defaultParams);
                text = `欢迎 ${defaultParams.nickname || defaultParams.username}！\n\n感谢您注册 ${defaultParams.systemName}。您的账户已成功激活。\n\n如果您有任何问题，请联系我们：${defaultParams.supportEmail}\n\n${defaultParams.systemName}`;
                break;

            case 'passwordChanged':
                subject = emailTemplates.passwordChanged.subject;
                html = this.getPasswordChangedTemplate(defaultParams);
                text = `您好 ${defaultParams.nickname || defaultParams.username}，\n\n您的账户密码已成功修改。如果这不是您本人的操作，请立即联系我们。\n\n联系邮箱：${defaultParams.supportEmail}\n\n${defaultParams.systemName}`;
                break;

            case 'notification':
                subject = template.subject;
                html = this.getNotificationTemplate(defaultParams);
                text = (defaultParams as any).message || '您有新的系统通知';
                break;

            default:
                throw new Error(`不支持的邮件模板类型: ${templateType}`);
        }

        return { subject, html, text };
    }

    /**
     * 获取激活邮件模板
     */
    private getActivationTemplate(params: EmailTemplateParams): string {
        return `
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>激活您的账户</title>
</head>
<body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
    <div style="max-width: 600px; margin: 0 auto; padding: 20px;">
        <h2 style="color: #2563eb;">激活您的账户</h2>
        <p>您好 ${params.nickname || params.username}，</p>
        <p>感谢您注册 ${params.systemName}！请点击下面的按钮激活您的账户：</p>
        <div style="text-align: center; margin: 30px 0;">
            <a href="${params.activationUrl}" style="background-color: #2563eb; color: white; padding: 12px 24px; text-decoration: none; border-radius: 5px; display: inline-block;">激活账户</a>
        </div>
        <p>或者您可以复制以下链接到浏览器地址栏：</p>
        <p style="word-break: break-all; background-color: #f3f4f6; padding: 10px; border-radius: 5px;">${params.activationUrl}</p>
        <p>激活码：<strong>${params.activationCode}</strong></p>
        <p><strong>注意：</strong>此链接将在 ${params.expireTime} 后过期。</p>
        <p>如果您没有注册账户，请忽略此邮件。</p>
        <hr style="margin: 30px 0; border: none; border-top: 1px solid #e5e7eb;">
        <p style="font-size: 14px; color: #6b7280;">
            此邮件由 ${params.systemName} 自动发送，请勿回复。<br>
            如有疑问，请联系：${params.supportEmail}
        </p>
    </div>
</body>
</html>`;
    }

    /**
     * 获取密码重置邮件模板
     */
    private getPasswordResetTemplate(params: EmailTemplateParams): string {
        return `
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>重置您的密码</title>
</head>
<body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
    <div style="max-width: 600px; margin: 0 auto; padding: 20px;">
        <h2 style="color: #dc2626;">重置您的密码</h2>
        <p>您好 ${params.nickname || params.username}，</p>
        <p>我们收到了重置您账户密码的请求。请点击下面的按钮重置密码：</p>
        <div style="text-align: center; margin: 30px 0;">
            <a href="${params.resetUrl}" style="background-color: #dc2626; color: white; padding: 12px 24px; text-decoration: none; border-radius: 5px; display: inline-block;">重置密码</a>
        </div>
        <p>或者您可以复制以下链接到浏览器地址栏：</p>
        <p style="word-break: break-all; background-color: #f3f4f6; padding: 10px; border-radius: 5px;">${params.resetUrl}</p>
        <p>重置码：<strong>${params.resetCode}</strong></p>
        <p><strong>注意：</strong>此链接将在 ${params.expireTime} 后过期。</p>
        <p>如果您没有请求重置密码，请忽略此邮件，您的密码不会被更改。</p>
        <hr style="margin: 30px 0; border: none; border-top: 1px solid #e5e7eb;">
        <p style="font-size: 14px; color: #6b7280;">
            此邮件由 ${params.systemName} 自动发送，请勿回复。<br>
            如有疑问，请联系：${params.supportEmail}
        </p>
    </div>
</body>
</html>`;
    }

    /**
     * 获取欢迎邮件模板
     */
    private getWelcomeTemplate(params: EmailTemplateParams): string {
        return `
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>欢迎加入</title>
</head>
<body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
    <div style="max-width: 600px; margin: 0 auto; padding: 20px;">
        <h2 style="color: #059669;">欢迎加入 ${params.systemName}！</h2>
        <p>您好 ${params.nickname || params.username}，</p>
        <p>感谢您注册 ${params.systemName}！您的账户已成功激活，现在可以开始使用我们的服务了。</p>
        <div style="background-color: #f0f9ff; padding: 20px; border-radius: 5px; margin: 20px 0;">
            <h3 style="color: #0369a1; margin-top: 0;">接下来您可以：</h3>
            <ul>
                <li>完善您的个人资料</li>
                <li>探索系统功能</li>
                <li>联系我们的客服团队</li>
            </ul>
        </div>
        <p>如果您在使用过程中遇到任何问题，请随时联系我们。</p>
        <hr style="margin: 30px 0; border: none; border-top: 1px solid #e5e7eb;">
        <p style="font-size: 14px; color: #6b7280;">
            此邮件由 ${params.systemName} 自动发送，请勿回复。<br>
            如有疑问，请联系：${params.supportEmail}
        </p>
    </div>
</body>
</html>`;
    }

    /**
     * 获取密码修改通知模板
     */
    private getPasswordChangedTemplate(params: EmailTemplateParams): string {
        return `
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>密码已修改</title>
</head>
<body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
    <div style="max-width: 600px; margin: 0 auto; padding: 20px;">
        <h2 style="color: #f59e0b;">密码修改通知</h2>
        <p>您好 ${params.nickname || params.username}，</p>
        <p>您的账户密码已成功修改。</p>
        <div style="background-color: #fef3c7; padding: 15px; border-radius: 5px; margin: 20px 0; border-left: 4px solid #f59e0b;">
            <p style="margin: 0;"><strong>修改时间：</strong> ${new Date().toLocaleString('zh-CN')}</p>
        </div>
        <p>如果这不是您本人的操作，请立即联系我们并采取以下措施：</p>
        <ul>
            <li>立即联系客服：${params.supportEmail}</li>
            <li>检查账户安全设置</li>
            <li>更改相关联的其他账户密码</li>
        </ul>
        <hr style="margin: 30px 0; border: none; border-top: 1px solid #e5e7eb;">
        <p style="font-size: 14px; color: #6b7280;">
            此邮件由 ${params.systemName} 自动发送，请勿回复。<br>
            如有疑问，请联系：${params.supportEmail}
        </p>
    </div>
</body>
</html>`;
    }

    /**
     * 获取通知邮件模板
     */
    private getNotificationTemplate(params: EmailTemplateParams): string {
        const message = (params as any).message || '您有新的系统通知，请登录查看详情。';
        return `
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>系统通知</title>
</head>
<body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
    <div style="max-width: 600px; margin: 0 auto; padding: 20px;">
        <h2 style="color: #6366f1;">系统通知</h2>
        <p>您好 ${params.nickname || params.username}，</p>
        <div style="background-color: #f8fafc; padding: 20px; border-radius: 5px; margin: 20px 0;">
            ${message}
        </div>
        <hr style="margin: 30px 0; border: none; border-top: 1px solid #e5e7eb;">
        <p style="font-size: 14px; color: #6b7280;">
            此邮件由 ${params.systemName} 自动发送，请勿回复。<br>
            如有疑问，请联系：${params.supportEmail}
        </p>
    </div>
</body>
</html>`;
    }

    /**
     * 执行健康检查
     */
    public async healthCheck(): Promise<EmailHealthCheckResult> {
        const startTime = Date.now();

        try {
            if (!this._transporter) {
                return {
                    status: 'unhealthy',
                    responseTime: 0,
                    serviceStatus: this.status,
                    error: '邮件传输器未初始化',
                };
            }

            // 验证SMTP连接
            await this._transporter.verify();
            const responseTime = Date.now() - startTime;

            this.updateStatus('healthy', 'connected');

            return {
                status: 'healthy',
                responseTime,
                serviceStatus: this.status,
            };
        } catch (error) {
            const errorMessage = error instanceof Error ? error.message : String(error);
            this.updateStatus('unhealthy', 'error', errorMessage);

            return {
                status: 'unhealthy',
                responseTime: Date.now() - startTime,
                serviceStatus: this.status,
                error: errorMessage,
            };
        }
    }

    /**
     * 关闭邮件服务
     */
    public async close(): Promise<void> {
        try {
            if (this._transporter) {
                this._transporter.close();
                this._transporter = null;
            }

            this._isInitialized = false;
            this.updateStatus('unhealthy', 'disconnected');

            Logger.debug('邮件服务已关闭');
        } catch (error) {
            Logger.error(error instanceof Error ? error : new Error('关闭邮件服务时出错'));
        }
    }
}

// 创建单例实例
const emailService = EmailService.getInstance();

// 导出便捷方法
export const initializeEmailService = () => emailService.initialize();
export const sendEmail = (options: EmailSendOptions) => emailService.sendEmail(options);
export const sendTemplateEmail = (options: EmailTemplateSendOptions) => emailService.sendTemplateEmail(options);
export const getEmailServiceStatus = () => emailService.status;
export const checkEmailServiceHealth = () => emailService.healthCheck();
export const closeEmailService = () => emailService.close();

// 导出服务实例
export { emailService };