import fs from 'node:fs';
import net from 'node:net';
import path from 'node:path';
import process from 'node:process';
import { spawn } from 'node:child_process';
import { fileURLToPath } from 'node:url';
import { loadConnectionConfig } from './remote-access-common.mjs';

const ROOT_DIR = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');
const ACCESS_DIR = path.join(ROOT_DIR, '.remote-access');
const CONNECTION_PATH = path.join(ACCESS_DIR, 'connection.json');
const RESTART_MARKER_PATH = path.join(ACCESS_DIR, 'restart-requested.json');

/**
 * 解析后端实际监听端口。
 * 优先级：CANGKU_BACKEND_PORT 环境变量 > backend/.env 的 PORT > 默认 4001。
 * 前端 dev server 的 /api 代理必须指向同一端口，否则请求会被转发到空端口。
 */
function resolveBackendPort() {
  const fromEnv = Number(process.env.CANGKU_BACKEND_PORT);
  if (Number.isInteger(fromEnv) && fromEnv > 0 && fromEnv < 65536) {
    return fromEnv;
  }

  const envPath = path.join(ROOT_DIR, 'backend', '.env');
  if (fs.existsSync(envPath)) {
    const matched = fs.readFileSync(envPath, 'utf8').match(/^PORT=(\d+)\s*$/mu);
    const fromFile = Number(matched?.[1]);
    if (Number.isInteger(fromFile) && fromFile > 0 && fromFile < 65536) {
      return fromFile;
    }
  }

  return 4001;
}

export function buildSshArgs(config) {
  return [
    '-N', '-T',
    '-o', 'BatchMode=yes',
    '-o', 'ExitOnForwardFailure=yes',
    '-o', 'ServerAliveInterval=30',
    '-o', 'ServerAliveCountMax=3',
    '-o', 'StrictHostKeyChecking=yes',
    '-o', `UserKnownHostsFile=${path.join(ACCESS_DIR, 'known_hosts')}`,
    '-o', `CertificateFile=${path.join(ACCESS_DIR, 'id_ed25519-cert.pub')}`,
    '-i', path.join(ACCESS_DIR, 'id_ed25519'),
    '-p', String(config.ssh.port),
    '-L', `127.0.0.1:${config.localDatabasePort}:${config.ssh.remoteDatabaseHost}:${config.ssh.remoteDatabasePort}`,
    `${config.ssh.user}@${config.ssh.host}`,
  ];
}

function waitForPort(port, timeoutMs = 60000) {
  const started = Date.now();
  return new Promise((resolve, reject) => {
    const attempt = () => {
      const socket = net.createConnection({ host: '127.0.0.1', port });
      socket.once('connect', () => {
        socket.destroy();
        resolve();
      });
      socket.once('error', () => {
        socket.destroy();
        if (Date.now() - started >= timeoutMs) {
          reject(new Error(`SSH 隧道未能在 ${timeoutMs / 1000} 秒内监听端口 ${port}`));
          return;
        }
        setTimeout(attempt, 250);
      });
    };
    attempt();
  });
}

function waitForFile(filePath) {
  return new Promise((resolve) => {
    const timer = setInterval(() => {
      if (fs.existsSync(filePath)) {
        clearInterval(timer);
        resolve();
      }
    }, 500);
  });
}

function waitForExit(child, timeoutMs = 5000) {
  if (child.exitCode !== null || child.signalCode !== null) return Promise.resolve();
  return Promise.race([
    new Promise((resolve) => child.once('exit', resolve)),
    new Promise((resolve) => setTimeout(resolve, timeoutMs)),
  ]);
}

export async function main(mode = process.argv[2] || 'tunnel') {
  if (!['tunnel', 'dev', 'backend'].includes(mode)) {
    throw new Error(`未知启动模式：${mode}`);
  }

  const children = new Set();
  let shuttingDown = false;
  let restartingBackend = false;
  let backend = null;

  const stopChildren = () => {
    shuttingDown = true;
    for (const child of children) {
      if (!child.killed) child.kill('SIGTERM');
    }
  };
  for (const signal of ['SIGINT', 'SIGTERM']) {
    process.once(signal, stopChildren);
  }

  const startTunnel = async () => {
    const { value: config } = loadConnectionConfig(ROOT_DIR);
    const tunnel = spawn('ssh', buildSshArgs(config), { cwd: ROOT_DIR, stdio: 'inherit' });
    children.add(tunnel);
    let ready = false;
    const earlyExit = new Promise((resolve, reject) => {
      tunnel.once('exit', (code) => {
        children.delete(tunnel);
        if (!ready) {
          reject(new Error(`SSH 隧道在建立前退出（${code ?? 'unknown'}）`));
        } else if (!shuttingDown) {
          console.error(`SSH 隧道已退出（${code ?? 'unknown'}）`);
          stopChildren();
          process.exitCode = code || 1;
        }
      });
    });
    try {
      await Promise.race([waitForPort(Number(config.localDatabasePort)), earlyExit]);
      ready = true;
    } catch (error) {
      if (!tunnel.killed) tunnel.kill('SIGTERM');
      throw error;
    }
    console.log(`系统数据库隧道已建立：127.0.0.1:${config.localDatabasePort}/${config.databaseName}`);
    return tunnel;
  };

  const npmCommand = process.platform === 'win32' ? 'npm.cmd' : 'npm';
  const startApplication = (args, kind) => {
    const childEnvironment = {
      ...process.env,
      CANGKU_REMOTE_SUPERVISOR: 'true',
    };
    if (kind === 'frontend' && !childEnvironment.VITE_API_PROXY_TARGET) {
      childEnvironment.VITE_API_PROXY_TARGET = `http://localhost:${resolveBackendPort()}`;
    }
    const child = spawn(npmCommand, args, {
      cwd: ROOT_DIR,
      stdio: 'inherit',
      env: childEnvironment,
      // Windows 下 .cmd 不是可执行文件，必须经 shell 启动，否则 spawn 直接抛 EINVAL
      shell: process.platform === 'win32',
    });
    children.add(child);
    child.once('exit', (code) => {
      children.delete(child);
      if (kind === 'backend' && restartingBackend) return;
      if (!shuttingDown) {
        console.error(`${kind === 'backend' ? '后端' : '前端'}进程已退出（${code ?? 'unknown'}）`);
        stopChildren();
        process.exitCode = code || 1;
      }
    });
    return child;
  };

  const hasConnection = fs.existsSync(CONNECTION_PATH);
  if (hasConnection) {
    if (fs.existsSync(RESTART_MARKER_PATH)) fs.unlinkSync(RESTART_MARKER_PATH);
    await startTunnel();
  } else if (mode === 'tunnel') {
    throw new Error('尚未配置远程系统数据库，请先运行应用并在首次启动弹窗中输入请求地址和 API Key');
  }

  if (mode === 'tunnel') return;

  backend = startApplication(
    ['--prefix', 'backend', 'run', mode === 'dev' ? 'dev' : 'start'],
    'backend'
  );
  if (mode === 'dev') {
    startApplication(['--prefix', 'frontend', 'run', 'dev'], 'frontend');
  }

  if (!hasConnection) {
    console.log('首次启动：请在安装页面输入配置请求地址和 API Key。');
    await waitForFile(RESTART_MARKER_PATH);
    restartingBackend = true;
    if (!backend.killed) backend.kill('SIGTERM');
    await waitForExit(backend);
    restartingBackend = false;
    fs.unlinkSync(RESTART_MARKER_PATH);
    await startTunnel();
    backend = startApplication(
      ['--prefix', 'backend', 'run', mode === 'dev' ? 'dev' : 'start'],
      'backend'
    );
  }
}

if (process.argv[1] === fileURLToPath(import.meta.url)) {
  main().catch((error) => {
    console.error(`远程运行启动失败：${error.message}`);
    process.exitCode = 1;
  });
}