using System;
using System.Diagnostics;
using System.IO;
using System.Text.Json;
using System.Threading;
using Notify.Serialization;

namespace Notify.Ipc;

/// <summary>
/// 基于落盘队列的非阻塞投递：CLI 写文件后立即返回，Host 监视目录消费
///
/// 取代命名管道，避免 CLI 在 Host 冷启动时被阻塞而拖住 Claude Code
/// </summary>
public static class NotificationSpool
{
    public static readonly string Dir =
        Path.Combine(Path.GetTempPath(), "claude-notify-spool");

    // CLI 侧：写入一条请求，必要时拉起 Host，全程不阻塞
    public static void Deliver(NotifyMessage message)
    {
        try
        {
            Directory.CreateDirectory(Dir);

            // 先写 .tmp 再原子改名为 .json，避免 Host 读到半截文件
            var id = Guid.NewGuid().ToString("N");
            var tmp = Path.Combine(Dir, id + ".tmp");
            var final = Path.Combine(Dir, id + ".json");
            File.WriteAllText(tmp, JsonSerializer.Serialize(message, AppJsonContext.Default.NotifyMessage));
            File.Move(tmp, final);
        }
        catch
        {
            // 写入失败则放弃这条通知，绝不影响调用方
        }

        EnsureHostRunning();
    }

    // Host 未运行则拉起（不等待）；运行中则什么都不做
    private static void EnsureHostRunning()
    {
        try
        {
            if (Mutex.TryOpenExisting(IpcConstants.HostMutexName, out var existing))
            {
                existing.Dispose();
                return;
            }
        }
        catch
        {
            // 打不开就当作未运行，继续尝试拉起
        }

        try
        {
            var exe = Environment.ProcessPath;
            if (exe is null)
            {
                return;
            }

            // 必须用 UseShellExecute=true 让 host 彻底脱离本进程的标准句柄
            // 否则常驻 host 会继承并攥住钩子的 stdout 管道，导致 Claude Code
            // 等不到管道 EOF 而卡在 "running stop hook"
            Process.Start(new ProcessStartInfo
            {
                FileName = exe,
                Arguments = "host",
                UseShellExecute = true,
                WindowStyle = ProcessWindowStyle.Hidden,
            });
        }
        catch
        {
            // 拉起失败则该通知会在下次 Host 启动时由 DrainExisting 补弹
        }
    }

    // Host 侧：消费单个 spool 文件并删除
    public static NotifyMessage? ReadAndRemove(string path)
    {
        try
        {
            var json = File.ReadAllText(path);
            File.Delete(path);
            return JsonSerializer.Deserialize(json, AppJsonContext.Default.NotifyMessage);
        }
        catch
        {
            return null;
        }
    }

    // Host 启动时把已有的 spool 文件补弹一遍
    public static void DrainExisting(Action<NotifyMessage> handler)
    {
        try
        {
            if (!Directory.Exists(Dir))
            {
                return;
            }

            foreach (var path in Directory.GetFiles(Dir, "*.json"))
            {
                if (ReadAndRemove(path) is { } msg)
                {
                    handler(msg);
                }
            }
        }
        catch
        {
            // 忽略
        }
    }
}