'use strict';

const nodemailer = require('nodemailer'),
  Email = require('email-templates'),
  hbs = require('handlebars'),
  assert = require('assert'),
  fs = require('fs-extra'),
  cloneDeep = require('clone-deep'),
  path = require('path'),
  utils = require('./utils'),
  env = require('./env'),
  { Errors, DEFAULT_LANG } = require('./constants'),
  { AppInputError, AppAuthError } = require('./app_error'),
  debug = require('debug')('agm:mailer');

const TemplateType = Object.freeze({
  PUG: 'pug', // default
  HANDLEBARS: 'hbs',
});

const Templates = Object.freeze({
  RESET_PASSWORD: 'reset-password',
  PASSWORD_RESET: 'password-reset',
  UPDATE_PAYMENT: 'update-payment',
  UPDATE_BILL_ADDRESS: 'update-address',
  CURRENT_SUBSCRIPTIONS: 'current-subscriptions',
  SUB_RENEWAL_REMIND: 'sub-renewal-remind',
  SUB_TRIAL_END_REMIND: 'sub-trial-end-remind',
  PROMO_EXPIRED: 'promo-expired',
  TEMPORARY_CREDENTIAL: 'temporary-credential',
  EMAIL_VERIFICATION: 'email-verification',
  NEW_ACCOUNT_WELCOME: 'new-account-welcome'
});

const transporter = nodemailer.createTransport({
  host: env.SMTP_HOST,
  port: env.SMTP_PORT,
  secure: env.SMTP_SECURE,
  auth: {
    user: env.SMTP_USR,
    pass: env.SMTP_PWD
  },
  // debug: true,
  // logger: true
});

function registerHbsPartials(partialsPath) {
  // Ref handlebars with vars in templates: https://github.com/forwardemail/email-templates/issues/283
  // hbs is your own instance of handlebars, with partials

  // Register all available partials under the emails' partials folder
  const partialDir = path.join(process.cwd() + partialsPath);
  // const partialFiles = 
  fs.readdir(partialDir, (err, partialFiles) => {
    if (!err && !utils.isEmptyArray(partialFiles)) {
      for (let i = 0; i < partialFiles.length; i++) {
        const pfile = partialFiles[i];
        hbs.registerPartial(path.basename(pfile, '.hbs'), require(path.join(partialDir, pfile)));
      }
      // Override consolidate's handlebars instance
      // email.config.views.options.engineSource.requires.handlebars = hbs;
    }
  });
}
registerHbsPartials('/emails/partials/');
hbs.registerHelper('$t', function (key, options) {
  // Translation helper to translate message by key or with hash
  const translation = options.data.root.t({ phrase: key, locale: options.data.root.locale }, options.hash);

  // Convert newline characters (\n) to <br/> tags for HTML emails
  if (translation) {
    return new hbs.SafeString(translation.replace(/\n/g, '<br/>'));
  }

  return '';
});

require('handlebars-helpers')(['comparison']);

const agmMailSig = ['Best,', 'AgMision Team'];

const debugging = false;

const defaultMailOps = {
  transport: transporter,
  preview: debugging,
  send: true,
  i18n: {
    locales: ['en', 'es', 'pt']
  }
};

function init(ops) {
  if (ops) {
    Object.assign({}, defaultMailOps, ops);
  }
}

function _toLocale(locals) {
  if (!utils.isEmptyObj(locals) && !utils.hasProperty(locals, 'locale')) {
    const _locals = cloneDeep(locals);
    _locals.locale = _locals.lang || DEFAULT_LANG;
    delete _locals.lang;
    return _locals;
  }
  return locals;
}

function getAppHostUrl(locals) {
  if (!locals || !locals.baseUrl) AppInputError.throw();

  return `${locals.baseUrl}/${locals.lang || DEFAULT_LANG}/#`;
}

/**
 * Send an email with given template and additional info
 * @param {*} template the template name
 * @param {*} locals additional metadata
 * @returns 
 */
async function sendMail(template, locals, to, from) {
  const email = await createEmail({ from: from, to: to });

  return email.send({
    template: template,
    // message: {
    //   to: to,
    // },
    locals: _toLocale(locals)
  });
}

/**
 * Send a text email from to with the mail options
 * @param {*} contentOps { subject: <the mail subject>, text: <the text body content> } 
 */
async function sendTextMail(contentOps, to, cc) {
  if (utils.isEmptyObj(contentOps)) {
    debug('Can not send Text email. No contentOps provided !');
    return;
  }

  const _mailOps = Object.assign(contentOps,
    {
      from: 'AgMission <noreply@agnav.com>',
      to: to || 'agm_admin@agnav.com'
    });
  if (cc) _mailOps.cc = cc;

  return transporter.sendMail(_mailOps);
}

/**
 * Send a text email to the admin.
 * @param {string} subject - The subject of the email.
 * @param {string} text - The body of the email.
 * @param {string} cc - The CC email address.
 */
async function sendAdminNotification(subject, text, cc) {
  return await sendTextMail({ subject, text }, '', cc);
}

/**
 * Create an Email instance
 * @param {*} emailOps  { from, to }
 */
async function createEmail(emailOps, templateType = TemplateType.PUG) {

  let _ops = Object.assign(
    {
      message: {
        from: emailOps && emailOps.from || 'AgMission <noreply@agnav.com>'
      }
    },
    defaultMailOps);
  if (templateType === 'hbs') {
    _ops = {
      ..._ops, views: {
        options: {
          extension: 'hbs'
        },
        engineSource: { requires: { handlebars: hbs } }
      },
      /* For relative assets or ones located within the same server */
      // juice: true,
      // juiceResources: {
      //   webResources: {
      //     images: true,
      //     // relativeTo: path.join(process.cwd(), '/emails/assets'),
      //   }
      // }
    }
  }

  if (emailOps && emailOps.to) {
    _ops.message.to = emailOps.to;
  }

  const email = new Email(_ops);
  return email;
}

async function sendHandlebarsEmail(template, locals, to, from = null) {

  if (env.NO_EMAIL_MODE) {
    debug('Email sending is disabled in the current mode.');
    return {
      success: false,
      messageId: null,
      error: 'Email sending is disabled in the current mode'
    };
  }

  assert(template, AppInputError.create(Errors.TEMPLATE_NOT_FOUND));
  assert(to, AppInputError.create(Errors.TO_NOT_FOUND));

  const email = await createEmail({ locale: 'en', to: to }, TemplateType.HANDLEBARS);

  try {
    const result = await email.send({
      template: template,
      locals: {
        ..._toLocale(locals)
      }
    });

    // Debug the full result structure to find where messageId is located
    // debug('Email send result structure:', JSON.stringify(result, null, 2));

    // Check if the email was accepted by the mail server
    if (result) {
      let messageId = null;

      // Try different possible locations for messageId
      if (result.originalMessage && result.originalMessage.messageId) {
        messageId = result.originalMessage.messageId;
      } else if (result.messageId) {
        messageId = result.messageId;
      } else if (result.envelope && result.envelope.messageId) {
        messageId = result.envelope.messageId;
      }

      // debug(`Email sent to ${to} successfully. MessageId: ${messageId || 'undefined'}`);
      return {
        success: true,
        messageId: messageId,
        result: result  // Include the full result for debugging if needed
      };
    } else {
      debug(`Email to ${to} has unknown status`);
      return { success: false, error: 'Unknown email status' };
    }
  } catch (error) {
    debug(`Failed to send email to ${to}: ${error.message}`);
    // Capture specific nodemailer errors
    const errorInfo = {
      success: false,
      error: error.message,
      code: error.code,
      responseCode: error.responseCode,
      command: error.command
    };
    // Log detailed error for debugging
    env.LOG_ALL_ERRORS && debug('Email sending error details:', errorInfo);
    return errorInfo;
  }
}

/**
 * Validate email sending by sending a test email
 * @param {string} toEmail - The email to test delivery to
 * @returns {Promise<Object>} Result of the test with success/error information
 */
async function validateEmailDelivery(toEmail) {
  assert(toEmail, AppInputError.create(Errors.TO_NOT_FOUND));

  try {
    // Try to ping the SMTP server first
    const pingResult = await transporter.verify();
    if (!pingResult) {
      return {
        success: false,
        error: 'Failed to connect to the SMTP server',
        smtpConnected: false
      };
    }

    // Send a basic test email
    const result = await transporter.sendMail({
      from: 'AgMission <noreply@agnav.com>',
      to: toEmail,
      subject: 'Email Validation Test',
      text: 'This is an automated test email to validate email delivery.',
      headers: {
        'X-Priority': '1', // Set high priority to help avoid spam folders
        'X-Test': 'Email-Validation'
      }
    });

    return {
      success: true,
      messageId: result.messageId,
      smtpConnected: true,
      response: result.response
    };
  } catch (error) {
    debug(`Email validation failure for ${toEmail}: ${error.message}`);
    return {
      success: false,
      error: error.message,
      smtpConnected: error.code !== 'ECONNECTION',
      code: error.code,
      responseCode: error.responseCode
    };
  }
}

/**
 * Send update payment email notification so the customer can decide to update with a new payment method to continue using services
 * @param {*} locals  { locale: 'en', name, pmType: 'American Visa', pmEnding: '4321', baseUrl: 'https://localhost' }
 * @param {*} to the destination email address.
 * @param {*} from (Optional) the sender email address.
 */
async function _sendUpdatePaymentEmail(locals, to, from) {
  assert(locals && locals.name && locals.baseUrl, AppInputError.create());

  locals.updatePmUrl = `${getAppHostUrl(locals)}/update-pm`;
  return await sendHandlebarsEmail(Templates.UPDATE_PAYMENT, locals, to, from);
}

const sendUpdatePaymentEmail = withBaseUrl(_sendUpdatePaymentEmail);

/**
 * Send update Billing Address email notification so the customer can decide to update with a valid address (for tax purpose).
 * @param {*} locals  { locale: 'en', userId, name, address: {line1, line2, city, state, postalCode, Country (country name)}, baseUrl: 'https://localhost' }
 * @param {*} to the destination email address.
 * @param {*} from (Optional) the sender email address.
 */
async function _sendUpdateBillingAddressEmail(locals, to, from) {
  assert(locals && locals.userId && locals.name && locals.baseUrl && !utils.isEmptyObj(locals.address), AppInputError.create());

  locals.updateAddrUrl = `${getAppHostUrl(locals)}/update-bill-address/${locals.userId}`;
  return await sendHandlebarsEmail(Templates.UPDATE_BILL_ADDRESS, locals, to, from);
}

const sendUpdateBillingAddressEmail = withBaseUrl(_sendUpdateBillingAddressEmail);

/**
 * Send confirmation email with current subscriptions to the customer email address (normally after any subscription updates)
 * @param {*} locals  { locale: 'en', userId, name, package: [{ name, billCyle, startDate }], addon: [name, quantity, billCyle, startDate], baseUrl: 'https://localhost' }
 * @param {*} to the destination email address.
 * @param {*} from (Optional) the sender email address.
 */
async function _sendCurSubcriptionsEmail(locals, to, from) {
  assert(locals && locals.name && locals.baseUrl, AppInputError.create());

  return await sendHandlebarsEmail(Templates.CURRENT_SUBSCRIPTIONS, locals, to, from);
}

const sendCurSubcriptionsEmail = withBaseUrl(_sendCurSubcriptionsEmail);

/**
 * Send upcoming renewal reminder of a subscription to the customer (auto-renewal enabled)
 * @param {*} locals { name, prodsName, upPaymentDate, cardType, cardEnding, userId, baseUrl: 'https://localhost' }
 * @param {*} to the destination email address.
 * @param {*} from (Optional) the sender email address.
 *  */
async function _sendSubRenewalRemindEmail(locals, to, from) {
  assert(locals && locals.name && locals.baseUrl, AppInputError.create());

  locals.manageSubUrl = `${getAppHostUrl(locals)}/manage-subscription`;
  return await sendHandlebarsEmail(Templates.SUB_RENEWAL_REMIND, locals, to, from);
}

const sendSubRenewalRemindEmail = withBaseUrl(_sendSubRenewalRemindEmail);

/** 
 * Send trial ending reminder of a subscription to the customer (auto-renewal enabled)
 * @param {*} locals { subName, upPmDate, cardType, cardEnding, chargeAmount, baseUrl: 'https://localhost' }
 * @param {*} to the destination email address.
 * @param {*} from (Optional) the sender email address.
 *  */
async function _sendSubTrialEndingRemindEmail(locals, to, from) {
  assert(locals && locals.name && locals.baseUrl, AppInputError.create());

  locals.manageSubUrl = `${getAppHostUrl(locals)}/manage-subscription/${locals.userId}`;
  return await sendHandlebarsEmail(Templates.SUB_TRIAL_END_REMIND, locals, to, from);
}

const sendSubTrialEndingRemindEmail = withBaseUrl(_sendSubTrialEndingRemindEmail);

/**
 * Send promo expired notification to the customer when their promotional discount has ended.
 * This is triggered when a subscription schedule completes (phase with coupon ends).
 * @param {*} locals { name, promoName, subType, promoDiscount, promoStartDate, promoEndDate, newBillingDate, chargeAmount, baseUrl: 'https://localhost' }
 * @param {*} to the destination email address.
 * @param {*} from (Optional) the sender email address.
 */
async function _sendPromoExpiredEmail(locals, to, from) {
  assert(locals && locals.name && locals.baseUrl, AppInputError.create());

  locals.manageSubUrl = `${getAppHostUrl(locals)}/manage-subscription`;
  return await sendHandlebarsEmail(Templates.PROMO_EXPIRED, locals, to, from);
}

const sendPromoExpiredEmail = withBaseUrl(_sendPromoExpiredEmail);

/**
 * Send reset password notification email with validation token to the user
 * @param {*} locals { locale, id, baseUrl, name (name/username), token }
 * @param {*} to the destination email address.
 * @param {*} from (Optional) the sender email address.
 **/
async function _sendResetPasswordEmail(locals, to, from) {
  assert(locals && locals.id && locals.baseUrl && locals.name && locals.token, AppInputError.create());
  locals.resetUrl = `${getAppHostUrl(locals)}/password-reset/${locals.id}/${encodeURIComponent(locals.token)}`;
  locals.resetPwdUrl = `${getAppHostUrl(locals)}/password-reset`;
  return await sendHandlebarsEmail(Templates.RESET_PASSWORD, locals, to, from);
}

const sendResetPasswordEmail = withBaseUrl(_sendResetPasswordEmail);

/**
 *  Send password already reset successfully notification email to the user
 * @param {*} locals { locale, baseUrl, name (name/username), username } 
 * @param {*} to the destination email address.
 * @param {*} from Optional
 **/
async function _sendPasswordResetEmail(locals, to, from) {
  assert(locals && locals.baseUrl && locals.name && locals.username, AppInputError.create());
  locals.resetPwdUrl = `${getAppHostUrl(locals)}/password-reset`;
  return await sendHandlebarsEmail(Templates.PASSWORD_RESET, locals, to, from);
}

const sendPasswordResetEmail = withBaseUrl(_sendPasswordResetEmail);

/** 
 * Send temporary username and password to the customer 
 * @param {*} locals { name, baseUrl, username, password }
 * @param {*} to the destination email address.
 * @param {*} from (Optional) the sender email address.
 *  */
async function _sendTempCredential(locals, to, from) {
  assert(locals && locals.name && locals.baseUrl && locals.username && locals.password, AppInputError.create());
  locals.loginUrl = `${getAppHostUrl(locals)}/login`;
  return await sendHandlebarsEmail(Templates.TEMPORARY_CREDENTIAL, locals, to, from);
}

const sendTempCredential = withBaseUrl(_sendTempCredential);

/**
 * Send email verification before allowing signup form submission
 * @param {*} locals { username, baseUrl, token, lang }
 * @param {*} to the destination email address.
 * @param {*} from (Optional) the sender email address.
 * @returns {Promise<Object>} Result of the email sending operation
 */
async function _sendEmailVerificationCode(locals, to, from = null) {
  assert(locals && locals.username && locals.baseUrl && locals.token, AppInputError.create(Errors.TO_NOT_FOUND));
  // Create verification URL with token
  locals.verificationUrl = `${getAppHostUrl(locals)}/signup/verify-email?token=${encodeURIComponent(locals.token)}`;
  return await sendHandlebarsEmail(Templates.EMAIL_VERIFICATION, locals, to || locals.username, from);
}

const sendEmailVerificationCode = withBaseUrl(_sendEmailVerificationCode);

/**
 * Send welcome email to the newly created account
 * @param {*} locals { locale, name, username, orgName, baseUrl, accountType(optional) }
 * @param {*} to the destination email address.
 * @param {*} from (Optional) the sender email address.
 * @returns {Promise<Object>} Result of the email sending operation
 */
async function _sendWelcomeNewAccEmail(locals, to, from = null) {
  assert(locals && locals.name && locals.baseUrl && locals.username && locals.orgName, AppInputError.create());
  locals.resetPwdUrl = `${getAppHostUrl(locals)}/password-reset`;
  locals.manualUrl = 'https://www.agnav.com/manuals/';
  locals.loginUrl = `${getAppHostUrl(locals)}/login`;
  return await sendHandlebarsEmail(Templates.NEW_ACCOUNT_WELCOME, locals, to || locals.username, from);
}

const sendWelcomeNewAccEmail = withBaseUrl(_sendWelcomeNewAccEmail);

/**
 * Decorator function that extracts baseUrl from request and injects it into locals
 * @param {Function} emailFunction - The original email function to wrap
 * @returns {Function} - Enhanced function that extracts baseUrl from req parameter
 */
function withBaseUrl(emailFunction) {
  return async function(reqOrLocals, to, from) {
    let locals;
    // Always use environment variable if set
    const envBaseUrl = process.env.BASE_URL || process.env.APP_URL;
    if (!reqOrLocals || typeof reqOrLocals !== 'object') {
      locals = { baseUrl: envBaseUrl || `https://${env.PRODUCTION ? 'agmission.agnav.com' : 'localhost:4200'}` };
    }
    // If first parameter is a request object (check for common Express request properties)
    else if (reqOrLocals.protocol || reqOrLocals.headers || reqOrLocals.get || 
             reqOrLocals.hostname || reqOrLocals.method || reqOrLocals.url) {
      const req = reqOrLocals;
      let baseUrl = envBaseUrl;
      if (!baseUrl) {
        try {
          if (req.protocol && typeof req.get === 'function') {
            const host = req.get('host');
            if (host) {
              baseUrl = `${req.protocol}://${host}`;
            }
          } else if (req.hostname) {
            const protocol = req.secure || req.connection?.encrypted ? 'https' : 'http';
            const port = typeof req.get === 'function' ? req.get('x-forwarded-port') : null;
            baseUrl = `${protocol}://${req.hostname}${port && port !== '80' && port !== '443' ? ':' + port : ''}`;
          }
        } catch (error) {
          debug('Error extracting baseUrl from request:', error.message);
        }
      }
      if (!baseUrl) {
        baseUrl = `https://${env.PRODUCTION ? 'agmission.agnav.com' : 'localhost:4200'}`;
      }
      locals = (req.locals && typeof req.locals === 'object') ? { ...req.locals, baseUrl } : { baseUrl };
    } else {
      locals = reqOrLocals || {};
      // Always override baseUrl with environment variable if set
      locals.baseUrl = envBaseUrl || locals.baseUrl || `https://${env.PRODUCTION ? 'agmission.agnav.com' : 'localhost:4200'}`;
    }
    return await emailFunction(locals, to, from);
  };
}

// NOTE: For Testing only
async function sendTestMail(req, res) {

  let sent = true;
  try {
    // const custId = '5a1d6c05ffb94e7875c68dd9';
    // const updateUrl = `https://${req.hostname}/update-pm/${custId}`;

    // await sendHandlebarsEmail(
    //   Templates.UPDATE_PAYMENT,
    //   { locale: 'en', name: 'Trung Hoang', pmType: 'American Visa', pmEnding: '4321', updatePmUrl: updateUrl },
    //   'trungh@agnav.com',
    // );

    return await sendHandlebarsEmail(
      Templates.CURRENT_SUBSCRIPTIONS,
      {
        name: "Trung Hoang",
        // package: [{ name: "ess_2", billCycle: "year", startDate: utils.timestampToDate(1692720405) }],
        // addon: [{ name: "addon_1", billCycle: "month", quantity: 1, startDate: utils.timestampToDate(1692720405) }]
      },
      'trungh@agnav.com, trungduyhoang@gmail.com',
    );
  } catch (err) {
    debug(err);
    sent = false;
  }

  res.send({ msg: `Message sent ${sent}` }).end();
}


module.exports = {
  agmMailSig, sendTestMail, sendMail, sendTextMail, sendAdminNotification,
  sendUpdatePaymentEmail, sendUpdateBillingAddressEmail, sendCurSubcriptionsEmail, sendSubTrialEndingRemindEmail, sendSubRenewalRemindEmail,
  sendTempCredential, sendPasswordResetEmail, sendResetPasswordEmail, validateEmailDelivery, sendEmailVerificationCode, sendWelcomeNewAccEmail,
  sendPromoExpiredEmail, withBaseUrl
}