const { exec } = require('child_process');

const CHECK_INTERVAL = 30 * 1000;   // 每 30 秒检查一次
const IDLE_LIMIT = 60 * 1000;       // 空闲超过 60 秒则触发

// 封装执行 PowerShell 的方法（使用 UTF-16LE 编码避免引号转义问题）
function runPs(script) {
  return new Promise((resolve, reject) => {
    const encoded = Buffer.from(script, 'utf16le').toString('base64');
    exec(`powershell -NoProfile -EncodedCommand "${encoded}"`, (err, stdout) => {
      if (err) reject(err);
      else resolve(stdout.trim());
    });
  });
}

// 获取当前系统空闲毫秒数
async function getIdleTime() {
  const ps = `
  Add-Type @"
  using System;
  using System.Runtime.InteropServices;
  public class IdleChecker {
      [DllImport("user32.dll")]
      public static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);
      public struct LASTINPUTINFO {
          public uint cbSize;
          public uint dwTime;
      }
      public static uint GetIdleMilliseconds() {
          LASTINPUTINFO lii = new LASTINPUTINFO();
          lii.cbSize = (uint)Marshal.SizeOf(typeof(LASTINPUTINFO));
          GetLastInputInfo(ref lii);
          return (uint)Environment.TickCount - lii.dwTime;
      }
  }
  "@
  [IdleChecker]::GetIdleMilliseconds()
  `;
  const result = await runPs(ps);
  return parseInt(result, 10);
}

// 模拟按下 F15 键（无任何副作用）
async function pressF15() {
  const ps = `
  $wshell = New-Object -ComObject wscript.shell;
  $wshell.SendKeys('{F15}');
  `;
  await runPs(ps);
}

console.log('✅ 防锁屏脚本已启动 (PowerShell 模式)');
console.log(`⏱️  检测到空闲 ${IDLE_LIMIT/1000} 秒后，自动模拟按键防止锁屏。`);

setInterval(async () => {
  try {
    const idleMs = await getIdleTime();
    if (idleMs > IDLE_LIMIT) {
      console.log(`🔄 已空闲 ${Math.round(idleMs/1000)} 秒，模拟 F15 重置计时器...`);
      await pressF15();
    }
  } catch (e) {
    console.error('⚠️ 执行出错:', e.message);
  }
}, CHECK_INTERVAL);

// 按 Ctrl+C 退出时提示
process.on('SIGINT', () => {
  console.log('\n🛑 脚本已停止');
  process.exit(0);
});