/**
 * 邮件服务
 * 
 * 功能描述：
 * - 提供邮件发送的核心功能
 * - 支持多种邮件模板和场景
 * - 集成主流邮件服务提供商
 * 
 * 支持的邮件类型：
 * - 邮箱验证码
 * - 密码重置验证码
 * - 欢迎邮件
 * - 系统通知
 * 
 * @author moyin
 * @version 1.0.0
 * @since 2025-12-17
 */

import { Injectable, Logger, BadRequestException } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import * as nodemailer from 'nodemailer';
import { Transporter } from 'nodemailer';

/**
 * 邮件发送选项接口
 */
export interface EmailOptions {
  /** 收件人邮箱 */
  to: string;
  /** 邮件主题 */
  subject: string;
  /** 邮件内容（HTML格式） */
  html: string;
  /** 邮件内容（纯文本格式） */
  text?: string;
}

/**
 * 验证码邮件选项接口
 */
export interface VerificationEmailOptions {
  /** 收件人邮箱 */
  email: string;
  /** 验证码 */
  code: string;
  /** 用户昵称 */
  nickname?: string;
  /** 验证码用途 */
  purpose: 'email_verification' | 'password_reset';
}

@Injectable()
export class EmailService {
  private readonly logger = new Logger(EmailService.name);
  private transporter: Transporter;

  constructor(private readonly configService: ConfigService) {
    this.initializeTransporter();
  }

  /**
   * 初始化邮件传输器
   */
  private initializeTransporter(): void {
    const emailConfig = {
      host: this.configService.get<string>('EMAIL_HOST', 'smtp.gmail.com'),
      port: this.configService.get<number>('EMAIL_PORT', 587),
      secure: this.configService.get<boolean>('EMAIL_SECURE', false), // true for 465, false for other ports
      auth: {
        user: this.configService.get<string>('EMAIL_USER'),
        pass: this.configService.get<string>('EMAIL_PASS'),
      },
    };

    // 如果没有配置邮件服务，使用测试模式
    if (!emailConfig.auth.user || !emailConfig.auth.pass) {
      this.logger.warn('邮件服务未配置，将使用测试模式（邮件不会真实发送）');
      this.transporter = nodemailer.createTransport({
        streamTransport: true,
        newline: 'unix',
        buffer: true
      });
    } else {
      this.transporter = nodemailer.createTransport(emailConfig);
      this.logger.log('邮件服务初始化成功');
    }
  }

  /**
   * 发送邮件
   * 
   * @param options 邮件选项
   * @returns 发送结果
   */
  async sendEmail(options: EmailOptions): Promise<boolean> {
    try {
      const mailOptions = {
        from: this.configService.get<string>('EMAIL_FROM', '"Whale Town Game" <noreply@whaletown.com>'),
        to: options.to,
        subject: options.subject,
        html: options.html,
        text: options.text,
      };

      const result = await this.transporter.sendMail(mailOptions);
      
      // 如果是测试模式，输出邮件内容到控制台
      if ((this.transporter.options as any).streamTransport) {
        this.logger.log('=== 邮件发送（测试模式） ===');
        this.logger.log(`收件人: ${options.to}`);
        this.logger.log(`主题: ${options.subject}`);
        this.logger.log(`内容: ${options.text || '请查看HTML内容'}`);
        this.logger.log('========================');
      }

      this.logger.log(`邮件发送成功: ${options.to}`);
      return true;
    } catch (error) {
      this.logger.error(`邮件发送失败: ${options.to}`, error instanceof Error ? error.stack : String(error));
      return false;
    }
  }

  /**
   * 发送邮箱验证码
   * 
   * @param options 验证码邮件选项
   * @returns 发送结果
   */
  async sendVerificationCode(options: VerificationEmailOptions): Promise<boolean> {
    const { email, code, nickname, purpose } = options;

    let subject: string;
    let template: string;

    if (purpose === 'email_verification') {
      subject = '【Whale Town】邮箱验证码';
      template = this.getEmailVerificationTemplate(code, nickname);
    } else {
      subject = '【Whale Town】密码重置验证码';
      template = this.getPasswordResetTemplate(code, nickname);
    }

    return await this.sendEmail({
      to: email,
      subject,
      html: template,
      text: `您的验证码是：${code}，5分钟内有效，请勿泄露给他人。`
    });
  }

  /**
   * 发送欢迎邮件
   * 
   * @param email 邮箱地址
   * @param nickname 用户昵称
   * @returns 发送结果
   */
  async sendWelcomeEmail(email: string, nickname: string): Promise<boolean> {
    const subject = '🎮 欢迎加入 Whale Town！';
    const template = this.getWelcomeTemplate(nickname);

    return await this.sendEmail({
      to: email,
      subject,
      html: template,
      text: `欢迎 ${nickname} 加入 Whale Town 像素游戏世界！`
    });
  }

  /**
   * 获取邮箱验证模板
   * 
   * @param code 验证码
   * @param nickname 用户昵称
   * @returns HTML模板
   */
  private getEmailVerificationTemplate(code: string, nickname?: string): string {
    return `
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>邮箱验证</title>
    <style>
        body { font-family: Arial, sans-serif; line-height: 1.6; color: #333; }
        .container { max-width: 600px; margin: 0 auto; padding: 20px; }
        .header { background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); color: white; padding: 30px; text-align: center; border-radius: 10px 10px 0 0; }
        .content { background: #f9f9f9; padding: 30px; border-radius: 0 0 10px 10px; }
        .code-box { background: #fff; border: 2px dashed #667eea; padding: 20px; text-align: center; margin: 20px 0; border-radius: 8px; }
        .code { font-size: 32px; font-weight: bold; color: #667eea; letter-spacing: 5px; }
        .footer { text-align: center; margin-top: 20px; color: #666; font-size: 12px; }
        .warning { background: #fff3cd; border: 1px solid #ffeaa7; padding: 15px; border-radius: 5px; margin: 20px 0; }
    </style>
</head>
<body>
    <div class="container">
        <div class="header">
            <h1>🐋 Whale Town</h1>
            <p>邮箱验证</p>
        </div>
        <div class="content">
            <h2>你好${nickname ? ` ${nickname}` : ''}！</h2>
            <p>感谢您注册 Whale Town 像素游戏！为了确保您的账户安全，请使用以下验证码完成邮箱验证：</p>
            
            <div class="code-box">
                <div class="code">${code}</div>
                <p style="margin: 10px 0 0 0; color: #666;">验证码</p>
            </div>
            
            <div class="warning">
                <strong>⚠️ 安全提醒：</strong>
                <ul style="margin: 10px 0 0 20px;">
                    <li>验证码 5 分钟内有效</li>
                    <li>请勿将验证码泄露给他人</li>
                    <li>如非本人操作，请忽略此邮件</li>
                </ul>
            </div>
            
            <p>完成验证后，您就可以开始您的像素世界冒险之旅了！</p>
        </div>
        <div class="footer">
            <p>此邮件由系统自动发送，请勿回复</p>
            <p>© 2025 Whale Town Game. All rights reserved.</p>
        </div>
    </div>
</body>
</html>`;
  }

  /**
   * 获取密码重置模板
   * 
   * @param code 验证码
   * @param nickname 用户昵称
   * @returns HTML模板
   */
  private getPasswordResetTemplate(code: string, nickname?: string): string {
    return `
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>密码重置</title>
    <style>
        body { font-family: Arial, sans-serif; line-height: 1.6; color: #333; }
        .container { max-width: 600px; margin: 0 auto; padding: 20px; }
        .header { background: linear-gradient(135deg, #ff6b6b 0%, #ee5a24 100%); color: white; padding: 30px; text-align: center; border-radius: 10px 10px 0 0; }
        .content { background: #f9f9f9; padding: 30px; border-radius: 0 0 10px 10px; }
        .code-box { background: #fff; border: 2px dashed #ff6b6b; padding: 20px; text-align: center; margin: 20px 0; border-radius: 8px; }
        .code { font-size: 32px; font-weight: bold; color: #ff6b6b; letter-spacing: 5px; }
        .footer { text-align: center; margin-top: 20px; color: #666; font-size: 12px; }
        .warning { background: #fff3cd; border: 1px solid #ffeaa7; padding: 15px; border-radius: 5px; margin: 20px 0; }
    </style>
</head>
<body>
    <div class="container">
        <div class="header">
            <h1>🔐 密码重置</h1>
            <p>Whale Town 账户安全</p>
        </div>
        <div class="content">
            <h2>你好${nickname ? ` ${nickname}` : ''}！</h2>
            <p>我们收到了您的密码重置请求。请使用以下验证码来重置您的密码：</p>
            
            <div class="code-box">
                <div class="code">${code}</div>
                <p style="margin: 10px 0 0 0; color: #666;">密码重置验证码</p>
            </div>
            
            <div class="warning">
                <strong>🛡️ 安全提醒：</strong>
                <ul style="margin: 10px 0 0 20px;">
                    <li>验证码 5 分钟内有效</li>
                    <li>请勿将验证码泄露给他人</li>
                    <li>如非本人操作，请立即联系客服</li>
                    <li>重置密码后请妥善保管新密码</li>
                </ul>
            </div>
            
            <p>如果您没有请求重置密码，请忽略此邮件，您的账户仍然安全。</p>
        </div>
        <div class="footer">
            <p>此邮件由系统自动发送，请勿回复</p>
            <p>© 2025 Whale Town Game. All rights reserved.</p>
        </div>
    </div>
</body>
</html>`;
  }

  /**
   * 获取欢迎邮件模板
   * 
   * @param nickname 用户昵称
   * @returns HTML模板
   */
  private getWelcomeTemplate(nickname: string): string {
    return `
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>欢迎加入 Whale Town</title>
    <style>
        body { font-family: Arial, sans-serif; line-height: 1.6; color: #333; }
        .container { max-width: 600px; margin: 0 auto; padding: 20px; }
        .header { background: linear-gradient(135deg, #4ecdc4 0%, #44a08d 100%); color: white; padding: 30px; text-align: center; border-radius: 10px 10px 0 0; }
        .content { background: #f9f9f9; padding: 30px; border-radius: 0 0 10px 10px; }
        .feature-box { background: #fff; padding: 20px; margin: 15px 0; border-radius: 8px; border-left: 4px solid #4ecdc4; }
        .footer { text-align: center; margin-top: 20px; color: #666; font-size: 12px; }
    </style>
</head>
<body>
    <div class="container">
        <div class="header">
            <h1>🎮 欢迎加入 Whale Town！</h1>
            <p>像素世界的冒险即将开始</p>
        </div>
        <div class="content">
            <h2>欢迎你，${nickname}！</h2>
            <p>恭喜您成功注册 Whale Town 像素游戏！您现在已经成为我们像素世界大家庭的一员了。</p>
            
            <div class="feature-box">
                <h3>🏗️ 建造与创造</h3>
                <p>在像素世界中建造您的梦想家园，发挥无限创意！</p>
            </div>
            
            <div class="feature-box">
                <h3>🤝 社交互动</h3>
                <p>与其他玩家交流互动，结交志同道合的朋友！</p>
            </div>
            
            <div class="feature-box">
                <h3>🎯 任务挑战</h3>
                <p>完成各种有趣的任务，获得丰厚的奖励！</p>
            </div>
            
            <p><strong>现在就开始您的像素冒险之旅吧！</strong></p>
            <p>如果您在游戏过程中遇到任何问题，随时可以联系我们的客服团队。</p>
        </div>
        <div class="footer">
            <p>祝您游戏愉快！</p>
            <p>© 2025 Whale Town Game. All rights reserved.</p>
        </div>
    </div>
</body>
</html>`;
  }

  /**
   * 验证邮件服务配置
   * 
   * @returns 验证结果
   */
  async verifyConnection(): Promise<boolean> {
    try {
      await this.transporter.verify();
      this.logger.log('邮件服务连接验证成功');
      return true;
    } catch (error) {
      this.logger.error('邮件服务连接验证失败', error instanceof Error ? error.stack : String(error));
      return false;
    }
  }
}