import nodemailer from "nodemailer";
import type { EmailEncryptionMode } from "./global-settings";

/**
 * A small, standalone nodemailer call — Manager and the main app are
 * separate deployable processes/images that share no code today (see
 * nextchair-manager's own package.json description); duplicating this
 * ~30-line transport setup is simpler than inventing a cross-package
 * shared module for one function, and mirrors the main app's own
 * src/services/notifications/providers/brevo-email-provider.ts closely
 * enough that a future shared package (if the two apps ever grow more
 * code in common) would be a mechanical extraction, not a rewrite.
 */
export interface TestEmailConfig {
  host: string;
  port: number;
  username: string;
  password: string;
  encryption: EmailEncryptionMode;
  fromAddress: string;
  fromName: string;
  replyTo: string;
  recipient: string;
}

export interface TestEmailResult {
  ok: boolean;
  message: string;
}

/**
 * Never rethrows the raw SMTP error to the caller — nodemailer/SMTP error
 * messages can echo back the configured username or other connection
 * details, and this result is ultimately shown in the browser. Categorized
 * instead: auth failure, connection failure, or a generic fallback.
 */
export async function sendTestSmtpEmail(config: TestEmailConfig): Promise<TestEmailResult> {
  const transporter = nodemailer.createTransport({
    host: config.host,
    port: config.port,
    secure: config.encryption === "tls",
    ignoreTLS: config.encryption === "none",
    auth: { user: config.username, pass: config.password },
    connectionTimeout: 10_000,
    greetingTimeout: 10_000,
    socketTimeout: 20_000,
  });

  try {
    await transporter.verify();
    await transporter.sendMail({
      from: config.fromName ? `"${config.fromName}" <${config.fromAddress}>` : config.fromAddress,
      to: config.recipient,
      replyTo: config.replyTo || undefined,
      subject: "NextChair test email",
      text: "This is a test email from your NextChair Manager Settings page — if you received this, your SMTP configuration is working.",
      html: "<p>This is a test email from your NextChair Manager Settings page — if you received this, your SMTP configuration is working.</p>",
    });
    return { ok: true, message: `Test email sent to ${config.recipient}.` };
  } catch (error) {
    return { ok: false, message: categorizeSmtpError(error) };
  } finally {
    transporter.close();
  }
}

export interface PlainEmailConfig extends Omit<TestEmailConfig, "recipient"> {
  recipient: string;
  subject: string;
  text: string;
}

/**
 * Same transport + error-categorising contract as sendTestSmtpEmail, for
 * the operator alert emails (health / backup failures). Plain text only;
 * never throws and never echoes raw SMTP errors.
 */
export async function sendPlainSmtpEmail(config: PlainEmailConfig): Promise<TestEmailResult> {
  const transporter = nodemailer.createTransport({
    host: config.host,
    port: config.port,
    secure: config.encryption === "tls",
    ignoreTLS: config.encryption === "none",
    auth: { user: config.username, pass: config.password },
    connectionTimeout: 10_000,
    greetingTimeout: 10_000,
    socketTimeout: 20_000,
  });
  try {
    await transporter.sendMail({
      from: config.fromName ? `"${config.fromName}" <${config.fromAddress}>` : config.fromAddress,
      to: config.recipient,
      replyTo: config.replyTo || undefined,
      subject: config.subject,
      text: config.text,
    });
    return { ok: true, message: `Sent to ${config.recipient}.` };
  } catch (error) {
    return { ok: false, message: categorizeSmtpError(error) };
  } finally {
    transporter.close();
  }
}

function categorizeSmtpError(error: unknown): string {
  const code = typeof error === "object" && error !== null && "code" in error ? String((error as { code?: unknown }).code) : "";
  const responseCode =
    typeof error === "object" && error !== null && "responseCode" in error
      ? Number((error as { responseCode?: unknown }).responseCode)
      : undefined;

  if (code === "EAUTH" || responseCode === 535) {
    return "Authentication failed — check the SMTP username and password.";
  }
  if (code === "ECONNECTION" || code === "ESOCKET" || code === "ECONNREFUSED") {
    return "Couldn't connect to the SMTP host — check the host, port, and encryption mode.";
  }
  if (code === "ETIMEDOUT") {
    return "Connection to the SMTP host timed out.";
  }
  if (code === "EENVELOPE") {
    return "The mail server rejected the sender or recipient address.";
  }
  return "Couldn't send the test email — check your SMTP settings and try again.";
}