import nodemailer, { type Transporter } from 'nodemailer';

import { env } from '@/lib/env';
import { logger } from '@/lib/logger';

/**
 * Creates and returns a new Nodemailer SMTP transporter.
 *
 * A new instance is created on each call so the factory can be used in
 * contexts where connection pooling is managed externally (e.g. per-request
 * in serverless, or once at worker startup).
 */
export function createTransporter(): Transporter {
  return nodemailer.createTransport({
    host: env.SMTP_HOST,
    port: env.SMTP_PORT,
    // Implicitly secure when port is 465; STARTTLS for all other ports.
    secure: env.SMTP_PORT === 465,
    ...(env.SMTP_USER && env.SMTP_PASS
      ? { auth: { user: env.SMTP_USER, pass: env.SMTP_PASS } }
      : {}),
  });
}

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

/**
 * Sends a single email via SMTP.
 *
 * Returns the nodemailer info object on success. Propagates errors to the
 * caller — callers in background jobs should wrap in try/catch and handle
 * retries via BullMQ.
 */
export async function sendEmail(
  to: string | string[],
  subject: string,
  html: string,
  from?: string,
  text?: string,
): Promise<nodemailer.SentMessageInfo> {
  const transporter = createTransporter();

  const requestedTo = Array.isArray(to) ? to.join(', ') : to;
  const effectiveTo = env.EMAIL_REDIRECT_TO ?? requestedTo;
  const effectiveSubject = env.EMAIL_REDIRECT_TO
    ? `[redirected from ${requestedTo}] ${subject}`
    : subject;

  const info = await transporter.sendMail({
    from: from ?? env.SMTP_FROM ?? `Port Nimara CRM <noreply@${env.SMTP_HOST}>`,
    to: effectiveTo,
    subject: effectiveSubject,
    html,
    ...(text ? { text } : {}),
  });

  logger.debug(
    { messageId: info.messageId, to: effectiveTo, originalTo: requestedTo, subject },
    env.EMAIL_REDIRECT_TO ? 'Email sent (redirected)' : 'Email sent',
  );

  return info;
}