import nodemailer from 'nodemailer';
import { getServerAppServices } from '@/lib/services/create-services.server';
import { config } from '../config';

let transporterInstance: nodemailer.Transporter | null = null;

function getTransporter() {
  if (transporterInstance) return transporterInstance;

  if (!config.mail.host) {
    throw new Error('MAIL_HOST is not configured. Please check your environment variables.');
  }

  transporterInstance = nodemailer.createTransport({
    host: config.mail.host,
    port: config.mail.port,
    secure: config.mail.port === 465,
    auth: {
      user: config.mail.user,
      pass: config.mail.pass,
    },
  });

  return transporterInstance;
}

interface SendEmailOptions {
  to?: string | string[];
  replyTo?: string;
  subject: string;
  html: string;
}

export async function sendEmail({ to, replyTo, subject, html }: SendEmailOptions) {
  const logger = getServerAppServices().logger.child({ component: 'mailer' });
  
  // Resolve recipients: priority to 'to' override, fallback to global MAIL_RECIPIENTS
  const resolvedTo = to || config.mail.recipients;
  
  // Normalize recipients (handle arrays or comma-strings)
  const recipients = Array.isArray(resolvedTo) 
    ? resolvedTo.join(', ') 
    : (resolvedTo?.toString() || '');

  if (!recipients || recipients.trim() === '') {
    logger.error('Email delivery ABORTED: No recipients configured', { 
      subject, 
      providedTo: to,
      configRecipients: config.mail.recipients 
    });
    return { success: false as const, error: 'No recipients configured' };
  }

  if (!config.mail.from) {
    logger.error('Email delivery ABORTED: MAIL_FROM is missing', { subject, recipients });
    return { success: false as const, error: 'MAIL_FROM is not configured' };
  }

  const mailOptions = {
    from: config.mail.from,
    to: recipients,
    replyTo,
    subject,
    html,
  };

  try {
    const transporter = getTransporter();
    logger.info('Attempting to send email via SMTP', { 
      host: config.mail.host,
      subject, 
      recipients,
      hasReplyTo: !!replyTo 
    });

    const info = await transporter.sendMail(mailOptions);
    
    logger.info('Email sent successfully', { 
      messageId: info.messageId, 
      subject, 
      recipients,
      response: info.response 
    });
    
    return { success: true, messageId: info.messageId };
  } catch (error) {
    const errorMsg = error instanceof Error ? error.message : String(error);
    logger.error('SMTP Transport failed', { 
      error: errorMsg, 
      subject, 
      recipients,
      config: {
        host: config.mail.host,
        user: config.mail.user ? '***' : 'not set'
      }
    });
    return { success: false, error: errorMsg };
  }
}