using System;
using System.Diagnostics;
using System.IO;
using System.Net.Http;
using System.Threading;
using IvfTl.Watchdog.Core;

namespace IvfTl.Watchdog
{
    /// <summary>
    /// control 崩溃看门狗(D3-05)。常驻探活 control /ping,崩溃自动重拉(读 DPAPI 缓存凭据)。
    /// 不依赖 operate 是否在跑。可 --pause/--resume(维护让路)、--stop(停这次)、--install/--uninstall(开机自启)。
    /// </summary>
    public static class Program
    {
        private const string MutexName = @"Global\ivf_tl_watchdog_singleton";
        private const string StopEventName = @"Global\ivf_tl_watchdog_stop";
        private const string RunKey = @"HKCU\Software\Microsoft\Windows\CurrentVersion\Run";
        private const string RunValueName = "ivf_tl_watchdog";

        private const int RelaunchCooldownSec = 30;     // 两次重拉最小间隔(防崩溃风暴)
        private const int MaxConsecutiveFailures = 5;    // 连续失败超此数 → 拉长冷却 + 告警
        private const int LongCooldownSec = 300;

        private static readonly HttpClient _http = new HttpClient { Timeout = TimeSpan.FromSeconds(2) };

        [STAThread]
        public static int Main(string[] args)
        {
            var a = WatchdogArgs.Parse(args);
            try
            {
                switch (a.Command)
                {
                    case WatchdogCommand.Install: return DoInstall(a);
                    case WatchdogCommand.Uninstall: return DoUninstall();
                    case WatchdogCommand.Pause: WatchdogPaths.SetPaused(true); Log("已暂停看门狗(只探活不重拉);--resume 恢复"); return 0;
                    case WatchdogCommand.Resume: WatchdogPaths.SetPaused(false); Log("已恢复看门狗守护"); return 0;
                    case WatchdogCommand.Stop: SignalStop(); Log("已向常驻看门狗发送停止信号"); return 0;
                    default: return RunLoop(a);
                }
            }
            catch (Exception ex)
            {
                Log("看门狗致命异常:" + ex);
                return 1;
            }
        }

        /// <summary>常驻探活循环。</summary>
        private static int RunLoop(WatchdogArgs a)
        {
            bool isNew;
            using (var mutex = new Mutex(true, MutexName, out isNew))
            {
                if (!isNew) { Log("已有看门狗实例在运行,本进程退出"); return 0; }

                using (var stopEvent = new EventWaitHandle(false, EventResetMode.ManualReset, StopEventName))
                {
                    Log($"看门狗启动 port={a.Port} interval={a.IntervalSec}s controlExe={ResolveControlExe()}");
                    int intervalMs = Math.Max(1, a.IntervalSec) * 1000;
                    DateTime lastRelaunchUtc = DateTime.MinValue;
                    int consecutiveFailures = 0;
                    bool? lastAlive = null;   // 状态变化才记日志,避免刷屏

                    while (true)
                    {
                        // 先判停止信号(--stop / --uninstall 触发):立刻优雅退出。
                        if (stopEvent.WaitOne(0)) { Log("收到停止信号,看门狗退出"); return 0; }

                        bool alive = IsControlAlive(a.Port);
                        if (alive != lastAlive) { Log(alive ? "control 存活(探活正常)" : "control 探活失败(不在)"); lastAlive = alive; }
                        if (alive)
                        {
                            consecutiveFailures = 0;
                        }
                        else
                        {
                            bool paused = WatchdogPaths.IsPaused();
                            bool stopped = WatchdogPaths.IsDeliberatelyStopped();
                            int cooldown = consecutiveFailures >= MaxConsecutiveFailures ? LongCooldownSec : RelaunchCooldownSec;
                            bool cooldownActive = (DateTime.UtcNow - lastRelaunchUtc).TotalSeconds < cooldown;

                            if (RelaunchDecision.ShouldRelaunch(alive, paused, stopped, cooldownActive))
                            {
                                var creds = CredentialStore.Load();
                                if (creds == null)
                                {
                                    Log($"control 不在,但无可用缓存凭据(creds.dat 存在={File.Exists(WatchdogPaths.CredsFile)});等 operate 首次拉起 control 后再守护");
                                }
                                else
                                {
                                    lastRelaunchUtc = DateTime.UtcNow;
                                    consecutiveFailures++;
                                    bool ok = Relaunch(creds, a.Port);
                                    if (ok && consecutiveFailures >= MaxConsecutiveFailures)
                                        Log($"⚠ control 已连续 {consecutiveFailures} 次重拉仍未稳定,冷却拉长至 {LongCooldownSec}s,请人工检查");
                                }
                            }
                            else if (paused) Log("control 不在,但看门狗处于暂停(--resume 恢复),不重拉");
                            else if (stopped) Log("control 不在,但为故意停机(受护栏 /shutdown),不重拉");
                            // cooldown 中静默等待,不刷屏
                        }

                        // 等一个周期;期间若收到停止信号则立刻醒来退出。
                        if (stopEvent.WaitOne(intervalMs)) { Log("收到停止信号,看门狗退出"); return 0; }
                    }
                }
            }
        }

        /// <summary>探活:control /ping 是否可达。</summary>
        private static bool IsControlAlive(int port)
        {
            try
            {
                var resp = _http.GetAsync($"http://127.0.0.1:{port}/ping").GetAwaiter().GetResult();
                return resp.IsSuccessStatusCode;
            }
            catch { return false; }
        }

        /// <summary>读缓存凭据,提权拉起 control(与 operate ControlProcessLauncher 同形态)。</summary>
        private static bool Relaunch(Credentials c, int port)
        {
            string exe = ResolveControlExe();
            if (!File.Exists(exe)) { Log("找不到 control.exe:" + exe); return false; }
            try
            {
                var psi = new ProcessStartInfo
                {
                    FileName = exe,
                    Arguments = $"--account={c.Account} --password={c.Password} --cacheDisk={c.CacheDisk} --port={port}",
                    UseShellExecute = true,            // requireAdministrator 子进程需 ShellExecute(看门狗已是管理员,不弹 UAC)
                    WindowStyle = ProcessWindowStyle.Hidden
                };
                Process.Start(psi);
                Log($"control 不在 → 已重拉 control.exe(port={port})");
                return true;
            }
            catch (Exception ex) { Log("重拉 control 失败:" + ex.Message); return false; }
        }

        /// <summary>control 可执行路径:默认与看门狗同目录(部署在同一 control\ 子目录)。</summary>
        private static string ResolveControlExe() =>
            Path.Combine(AppContext.BaseDirectory, "ivf_tl_ControlHost.exe");

        // ── 控制面 ──────────────────────────────────────────────

        private static int DoInstall(WatchdogArgs a)
        {
            string exe = Process.GetCurrentProcess().MainModule.FileName;
            string cmd = $"\"{exe}\" --port={a.Port} --interval={a.IntervalSec}";
            int rc = RunReg($"add \"{RunKey}\" /v {RunValueName} /t REG_SZ /d \"{cmd}\" /f");
            Log(rc == 0 ? $"已写开机自启:{cmd}" : "写开机自启失败 rc=" + rc);
            return rc;
        }

        private static int DoUninstall()
        {
            // 先停常驻实例,再删自启项 = 一条命令彻底卸载、无残留。
            SignalStop();
            int rc = RunReg($"delete \"{RunKey}\" /v {RunValueName} /f");
            Log(rc == 0 ? "已删除开机自启项,看门狗已卸载" : "删除开机自启项(可能本就不存在) rc=" + rc);
            return 0;
        }

        /// <summary>给常驻看门狗发停止信号(打开已存在的命名事件并置位);无常驻实例则静默。</summary>
        private static void SignalStop()
        {
            try
            {
                using (var ev = EventWaitHandle.OpenExisting(StopEventName)) ev.Set();
            }
            catch (WaitHandleCannotBeOpenedException) { Log("无常驻看门狗在运行(无需停止)"); }
            catch (Exception ex) { Log("发送停止信号异常:" + ex.Message); }
        }

        private static int RunReg(string arguments)
        {
            try
            {
                var psi = new ProcessStartInfo("reg.exe", arguments) { UseShellExecute = false, CreateNoWindow = true };
                var p = Process.Start(psi);
                p.WaitForExit();
                return p.ExitCode;
            }
            catch (Exception ex) { Log("reg.exe 执行异常:" + ex.Message); return -1; }
        }

        // ── 日志 ────────────────────────────────────────────────

        private static readonly object _logLock = new object();
        private static void Log(string msg)
        {
            string line = $"{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff}  {msg}";
            try
            {
                lock (_logLock)
                {
                    WatchdogPaths.EnsureDataDir();
                    File.AppendAllText(Path.Combine(WatchdogPaths.DataDir, "watchdog.log"), line + Environment.NewLine);
                }
            }
            catch { }
            try { Console.WriteLine(line); } catch { }
        }
    }
}