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

import {
  getVerificationEmailTemplate,
  getPasswordResetTemplate,
  getWelcomeEmailTemplate,
} from './templates';

export interface EmailOptions {
  to: string;
  subject: string;
  html: string;
  text?: string;
}

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

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

  private createTransporter() {
    const host = this.configService.get<string>('SMTP_HOST');
    const port = this.configService.get<number>('SMTP_PORT');
    const user = this.configService.get<string>('SMTP_USER');
    const pass = this.configService.get<string>('SMTP_PASS');

    if (!host || !user || !pass) {
      this.logger.warn('SMTP configuration incomplete. Emails will be logged only.');
      return;
    }

    this.transporter = nodemailer.createTransport({
      host,
      port: port || 465,
      secure: true, // SSL/TLS
      auth: {
        user,
        pass,
      },
    });

    // Verify connection
    this.transporter.verify((error) => {
      if (error) {
        this.logger.error('SMTP connection failed:', error);
      } else {
        this.logger.log('SMTP connection established successfully');
      }
    });
  }

  async sendEmail(options: EmailOptions): Promise<boolean> {
    const from = this.configService.get<string>('SMTP_FROM') ||
                 this.configService.get<string>('SMTP_USER');

    if (!this.transporter) {
      this.logger.warn('No SMTP transporter. Logging email instead:');
      this.logger.log(`To: ${options.to}`);
      this.logger.log(`Subject: ${options.subject}`);
      this.logger.log(`Body: ${options.text || 'HTML email'}`);
      return false;
    }

    try {
      const info = await this.transporter.sendMail({
        from: `"RE-QuestN" <${from}>`,
        to: options.to,
        subject: options.subject,
        html: options.html,
        text: options.text,
      });

      this.logger.log(`Email sent successfully: ${info.messageId}`);
      return true;
    } catch (error) {
      this.logger.error(`Failed to send email to ${options.to}:`, error);
      return false;
    }
  }

  // ==========================================
  // EMAIL VERIFICATION
  // ==========================================
  async sendVerificationEmail(email: string, token: string, name?: string): Promise<boolean> {
    const frontendUrl = this.configService.get<string>('FRONTEND_URL') || 'http://localhost:3000';
    const verificationUrl = `${frontendUrl}/verify-email?token=${token}`;

    const html = getVerificationEmailTemplate({ verificationUrl, name });
    const text = `Welcome to RE-QuestN! Please verify your email by clicking this link: ${verificationUrl}`;

    return this.sendEmail({
      to: email,
      subject: 'Verify Your Email - RE-QuestN',
      html,
      text,
    });
  }

  // ==========================================
  // PASSWORD RESET
  // ==========================================
  async sendPasswordResetEmail(email: string, resetUrl: string): Promise<boolean> {
    const html = getPasswordResetTemplate({ resetUrl });
    const text = `Reset your password by clicking this link: ${resetUrl}. This link will expire in 1 hour.`;

    return this.sendEmail({
      to: email,
      subject: 'Reset Your Password - RE-QuestN',
      html,
      text,
    });
  }

  // ==========================================
  // WELCOME EMAIL
  // ==========================================
  async sendWelcomeEmail(email: string, name?: string): Promise<boolean> {
    const frontendUrl = this.configService.get<string>('FRONTEND_URL') || 'http://localhost:3000';
    const html = getWelcomeEmailTemplate({ name, frontendUrl });
    const text = `Welcome to RE-QuestN, ${name || 'User'}! Your real estate journey starts now.`;

    return this.sendEmail({
      to: email,
      subject: 'Welcome to RE-QuestN!',
      html,
      text,
    });
  }
}