const brevo = require('@getbrevo/brevo');
const fs = require('fs');
const path = require('path');
const { logger } = require('../middleware/logger');

class MailService {
  constructor() {
    this.brevo = new brevo.TransactionalEmailsApi();
    this.brevo.setApiKey(
      brevo.TransactionalEmailsApiApiKeys.apiKey,
      process.env.BREVO_API_KEY
    );

    this.sender = {
      email: process.env.BREVO_SENDER_EMAIL,
      name: process.env.BREVO_SENDER_NAME,
    };

    this.loginUrl = process.env.LOGIN_URL;
    this.templatesDir = path.join(__dirname, '../mailTemplates');
  }

  // Helper to load and render a template
  renderTemplate(templateName, variables, lang = 'en') {
    logger.info('MailService.renderTemplate:start', { templateName, lang });
    // Supported languages
    const supportedLangs = ['en', 'de'];
    // Fallback to 'en' if unsupported or missing
    const chosenLang = supportedLangs.includes(lang) ? lang : 'en';
    const templatePath = path.join(this.templatesDir, chosenLang, templateName);
    let template;
    try {
      template = fs.readFileSync(templatePath, 'utf8');
      logger.info('MailService.renderTemplate:template_loaded', { templatePath, lang: chosenLang });
    } catch (err) {
      // Fallback to English if template not found
      if (chosenLang !== 'en') {
        const fallbackPath = path.join(this.templatesDir, 'en', templateName);
        template = fs.readFileSync(fallbackPath, 'utf8');
        logger.warn('MailService.renderTemplate:fallback_to_en', { fallbackPath, lang });
      } else {
        logger.error('MailService.renderTemplate:error', { templatePath, error: err.message });
        throw err;
      }
    }
    template = template.replace(/{{(\w+)}}/g, (_, key) => variables[key] || '');
    logger.info('MailService.renderTemplate:success', { templateName, lang: chosenLang });
    return template;
  }

  async sendRegistrationEmail({ email, firstName, lastName, userType, companyName, lang }) {
    logger.info('MailService.sendRegistrationEmail:start', { email, userType, lang });
    let subject, text;
    const chosenLang = lang || 'en';
    if (userType === 'personal') {
      subject = chosenLang === 'de'
        ? `Willkommen bei ProfitPlanet, ${firstName}!`
        : `Welcome to ProfitPlanet, ${firstName}!`;
      text = this.renderTemplate('registrationPersonal.txt', {
        firstName,
        lastName,
        loginUrl: this.loginUrl
      }, chosenLang);
    } else if (userType === 'company') {
      subject = chosenLang === 'de'
        ? `Willkommen bei ProfitPlanet, ${companyName}!`
        : `Welcome to ProfitPlanet, ${companyName}!`;
      text = this.renderTemplate('registrationCompany.txt', {
        companyName,
        loginUrl: this.loginUrl
      }, chosenLang);
    } else {
      subject = chosenLang === 'de'
        ? 'Willkommen bei ProfitPlanet!'
        : 'Welcome to ProfitPlanet!';
      text = chosenLang === 'de'
        ? `Danke für Ihre Registrierung bei ProfitPlanet!\nSie können sich jetzt hier anmelden: ${this.loginUrl}\n\nMit freundlichen Grüßen,\nProfitPlanet Team`
        : `Thank you for registering at ProfitPlanet!\nYou can now log in here: ${this.loginUrl}\n\nBest regards,\nProfitPlanet Team`;
    }

    try {
      const payload = new brevo.SendSmtpEmail();
      payload.sender = this.sender;
      payload.to = [{ email }];
      payload.subject = subject;
      payload.textContent = text;

      const data = await this.brevo.sendTransacEmail(payload);
      logger.info('MailService.sendRegistrationEmail:email_sent', { email, userType, lang: chosenLang });
      return data;
    } catch (error) {
      logger.error('MailService.sendRegistrationEmail:error', { email, error: error.message });
      throw error;
    }
  }

  async sendVerificationCodeEmail({ email, code, expiresAt, lang }) {
    logger.info('MailService.sendVerificationCodeEmail:start', { email, code, expiresAt, lang });
    const chosenLang = lang || 'en';
    const subject = chosenLang === 'de'
      ? 'Ihr ProfitPlanet E-Mail-Verifizierungscode'
      : 'Your ProfitPlanet Email Verification Code';
    const text = this.renderTemplate('verificationCode.txt', {
      code,
      expiresAt: expiresAt.toLocaleTimeString()
    }, chosenLang);

    try {
      const payload = new brevo.SendSmtpEmail();
      payload.sender = this.sender;
      payload.to = [{ email }];
      payload.subject = subject;
      payload.textContent = text;

      const data = await this.brevo.sendTransacEmail(payload);
      logger.info('MailService.sendVerificationCodeEmail:email_sent', { email, code, lang: chosenLang });
      return data;
    } catch (error) {
      logger.error('MailService.sendVerificationCodeEmail:error', { email, error: error.message });
      throw error;
    }
  }

  async sendLoginNotificationEmail({ email, ip, loginTime, userAgent, lang }) {
    logger.info('MailService.sendLoginNotificationEmail:start', { email, ip, loginTime, userAgent, lang });
    const chosenLang = lang || 'en';
    const subject = chosenLang === 'de'
      ? 'ProfitPlanet: Neue Login-Benachrichtigung'
      : 'ProfitPlanet: New Login Notification';
    const text = this.renderTemplate('loginNotification.txt', {
      email,
      ip,
      loginTime: loginTime.toLocaleString(),
      userAgent
    }, chosenLang);

    try {
      const payload = new brevo.SendSmtpEmail();
      payload.sender = this.sender;
      payload.to = [{ email }];
      payload.subject = subject;
      payload.textContent = text;

      const data = await this.brevo.sendTransacEmail(payload);
      logger.info('MailService.sendLoginNotificationEmail:email_sent', { email, ip, lang: chosenLang });
      return data;
    } catch (error) {
      logger.error('MailService.sendLoginNotificationEmail:error', { email, error: error.message });
      throw error;
    }
  }

  async sendPasswordResetEmail({ email, firstName, companyName, token, lang }) {
    logger.info('MailService.sendPasswordResetEmail:start', { email, token, lang });
    const chosenLang = lang || 'en';
    const subject = chosenLang === 'de'
      ? 'ProfitPlanet: Passwort zurücksetzen'
      : 'ProfitPlanet: Password Reset';
    const resetUrl = `${process.env.PASSWORD_RESET_URL || 'https://profit-planet.partners/password-reset-set'}?token=${token}`;
    const text = this.renderTemplate('passwordReset.txt', {
      firstName: firstName || '',
      companyName: companyName || '',
      resetUrl
    }, chosenLang);

    try {
      const payload = new brevo.SendSmtpEmail();
      payload.sender = this.sender;
      payload.to = [{ email }];
      payload.subject = subject;
      payload.textContent = text;

      const data = await this.brevo.sendTransacEmail(payload);
      logger.info('MailService.sendPasswordResetEmail:email_sent', { email, token, lang: chosenLang });
      return data;
    } catch (error) {
      logger.error('MailService.sendPasswordResetEmail:error', { email, error: error.message });
      throw error;
    }
  }
}

module.exports = new MailService();