import { createServer, type Server, type Socket } from 'node:net';
import { afterEach, describe, expect, it } from 'vitest';

import type { ChannelDeliveryInput } from './channel-delivery.js';
import { sendEmailNotification } from './smtp-sender.js';

interface FakePeer {
  readonly port: number;
  readonly lines: string[];
  stop(): Promise<void>;
}

const peers: FakePeer[] = [];

afterEach(async () => {
  for (const peer of peers.splice(0)) await peer.stop();
});

/**
 * Scripted SMTP peer. It answers one reply per command and stays quiet while a
 * message body streams in, which is how a real server behaves after `354`.
 */
function fakeServer(script: readonly string[]): Promise<FakePeer> {
  return new Promise((resolve) => {
    const lines: string[] = [];
    const sockets = new Set<Socket>();
    const server: Server = createServer((socket) => {
      sockets.add(socket);
      socket.once('close', () => sockets.delete(socket));
      let index = 0;
      let buffered = '';
      let inData = false;
      socket.write(`${script[index++] ?? '221 bye'}\r\n`);
      socket.on('data', (chunk) => {
        buffered += chunk.toString('utf8');
        let boundary = buffered.indexOf('\r\n');
        while (boundary >= 0) {
          const line = buffered.slice(0, boundary);
          buffered = buffered.slice(boundary + 2);
          boundary = buffered.indexOf('\r\n');
          lines.push(line);
          if (inData) {
            if (line === '.') inData = false;
            else continue;
          }
          if (line === 'DATA') inData = true;
          // A silent peer is deliberate: it lets a test assert the client timeout.
          const reply = script[index++];
          if (reply !== undefined) socket.write(`${reply}\r\n`);
        }
      });
    });
    server.listen(0, '127.0.0.1', () => {
      const address = server.address();
      const peer: FakePeer = {
        port: typeof address === 'object' && address ? address.port : 0,
        lines,
        stop: () =>
          new Promise<void>((done) => {
            for (const socket of sockets) socket.destroy();
            server.close(() => done());
          }),
      };
      peers.push(peer);
      resolve(peer);
    });
  });
}

function input(config: ChannelDeliveryInput['config']): ChannelDeliveryInput {
  return {
    type: 'email',
    config,
    title: '设备离线',
    body: 'SIM 卡所在设备已断开',
    eventType: 'device',
    occurredAt: '2026-09-03T08:00:00.000Z',
  };
}

// One reply per command: greeting, EHLO, AUTH LOGIN, user, password, MAIL FROM,
// two RCPT TO, DATA, the "." terminator, then QUIT.
const AUTH_SCRIPT = [
  '220 smtp ready',
  '250 ehlo',
  '334 ' + Buffer.from('Username:').toString('base64'),
  '334 ' + Buffer.from('Password:').toString('base64'),
  '235 authenticated',
  '250 sender ok',
  '250 recipient ok',
  '250 recipient ok',
  '354 send data',
  '250 message accepted',
  '221 bye',
];

const OPEN_SCRIPT = [
  '220 smtp ready',
  '250 ehlo',
  '250 sender ok',
  '250 recipient ok',
  '354 send data',
  '250 message accepted',
  '221 bye',
];

function messageLines(lines: readonly string[]): string[] {
  const start = lines.indexOf('DATA');
  return start < 0 ? [] : lines.slice(start + 1);
}

describe('sendEmailNotification', () => {
  it('runs AUTH LOGIN and submits one UTF-8 message per recipient', async () => {
    const peer = await fakeServer(AUTH_SCRIPT);
    const result = await sendEmailNotification(
      input({
        smtp_host: '127.0.0.1',
        smtp_port: peer.port,
        smtp_security: 'none',
        username: 'notify@example.test',
        password: 'p@ss',
        sender_address: 'notify@example.test',
        sender_name: 'SimAdmin 控制台',
        receiver_addresses: 'ops@example.test, admin@example.test',
        message_format: 'plain',
      }),
      2_000,
    );

    expect(result).toEqual({ ok: true });
    expect(peer.lines[0]).toMatch(/^EHLO /u);
    expect(peer.lines[1]).toBe('AUTH LOGIN');
    expect(peer.lines[2]).toBe(Buffer.from('notify@example.test').toString('base64'));
    expect(peer.lines[3]).toBe(Buffer.from('p@ss').toString('base64'));
    expect(peer.lines[4]).toBe('MAIL FROM:<notify@example.test>');
    expect(peer.lines.filter((line) => line.startsWith('RCPT TO:<'))).toEqual([
      'RCPT TO:<ops@example.test>',
      'RCPT TO:<admin@example.test>',
    ]);

    const message = messageLines(peer.lines);
    expect(message.at(-1)).toBe('.');
    const headers = message.slice(0, message.indexOf(''));
    expect(headers.join('\n')).toContain('Subject: =?UTF-8?B?');
    expect(headers.join('\n')).toContain('Content-Type: text/plain; charset=UTF-8');
    const payload = Buffer.from(
      message.slice(message.indexOf('') + 1, message.length - 1).join(''),
      'base64',
    ).toString('utf8');
    expect(payload).toBe('设备离线\n\nSIM 卡所在设备已断开');
  });

  it('switches the MIME subtype when the channel asks for HTML', async () => {
    const peer = await fakeServer(OPEN_SCRIPT);
    const result = await sendEmailNotification(
      input({
        smtp_host: '127.0.0.1',
        smtp_port: peer.port,
        smtp_security: 'none',
        sender_address: 'a@example.test',
        receiver_addresses: 'b@example.test',
        message_format: 'html',
      }),
      2_000,
    );
    expect(result).toEqual({ ok: true });
    expect(messageLines(peer.lines).join('\n')).toContain('Content-Type: text/html');
  });

  it('refuses to dial out when no receiver address is usable', async () => {
    await expect(
      sendEmailNotification(
        input({
          smtp_host: '127.0.0.1',
          smtp_port: 1,
          sender_address: 'notify@example.test',
          receiver_addresses: 'not-an-address',
        }),
        500,
      ),
    ).resolves.toEqual({ ok: false, detail: '缺少有效的收件地址' });
  });

  it('reports a rejected handshake instead of throwing', async () => {
    const peer = await fakeServer(['220 smtp ready', '421 service denied']);
    await expect(
      sendEmailNotification(
        input({
          smtp_host: '127.0.0.1',
          smtp_port: peer.port,
          smtp_security: 'none',
          sender_address: 'a@example.test',
          receiver_addresses: 'b@example.test',
        }),
        2_000,
      ),
    ).resolves.toMatchObject({ ok: false, detail: 'SMTP 返回 421：421 service denied' });
  });

  it('gives up with a readable detail when the server stops answering', async () => {
    const peer = await fakeServer(['220 smtp ready']);
    await expect(
      sendEmailNotification(
        input({
          smtp_host: '127.0.0.1',
          smtp_port: peer.port,
          smtp_security: 'none',
          sender_address: 'a@example.test',
          receiver_addresses: 'b@example.test',
        }),
        300,
      ),
    ).resolves.toMatchObject({ ok: false, detail: 'SMTP 响应超时' });
  });
});