using System;
using System.Diagnostics;
using System.IO;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

namespace Sln.Wcs.UI.Services;

public interface IEngineProcessService
{
    bool IsRunning { get; }
    string StatusText { get; }
    string? LastError { get; }
    event Action<string>? OutputReceived;
    event Action? StateChanged;
    Task StartAsync();
    void Stop();
}

public class EngineProcessService : IEngineProcessService
{
    private Process? _process;
    private readonly HttpClient _http = new() { Timeout = TimeSpan.FromSeconds(3) };
    private const string BaseUrl = "http://localhost:5100";
    private readonly StringBuilder _outputBuffer = new();

    public bool IsRunning { get; private set; }
    public string StatusText => IsRunning ? "运行中" : "已停止";
    public string? LastError { get; private set; }
    public event Action<string>? OutputReceived;
    public event Action? StateChanged;

    public async Task StartAsync()
    {
        if (IsRunning) return;
        LastError = null;
        _outputBuffer.Clear();

        var dllPath = Path.Combine(AppContext.BaseDirectory, "Sln.Wcs.HoistServer.dll");
        if (!File.Exists(dllPath))
            throw new InvalidOperationException($"找不到 {dllPath}");

        _process = new Process
        {
            StartInfo = new ProcessStartInfo
            {
                FileName = "dotnet",
                Arguments = $"\"{dllPath}\" --urls {BaseUrl}",
                UseShellExecute = false,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                CreateNoWindow = true,
            },
            EnableRaisingEvents = true,
        };

        _process.OutputDataReceived += (_, e) =>
        {
            if (e.Data != null) { _outputBuffer.AppendLine(e.Data); OutputReceived?.Invoke(e.Data); }
        };
        _process.ErrorDataReceived += (_, e) =>
        {
            if (e.Data != null) { _outputBuffer.AppendLine(e.Data); OutputReceived?.Invoke(e.Data); }
        };

        _process.Exited += (_, _) =>
        {
            IsRunning = false;
            StateChanged?.Invoke();
            _process?.Dispose();
            _process = null;
        };

        _process.Start();
        _process.BeginOutputReadLine();
        _process.BeginErrorReadLine();

        // 等待健康检查，最多 20 秒
        for (int i = 0; i < 40; i++)
        {
            await Task.Delay(500);
            if (_process.HasExited)
            {
                LastError = _outputBuffer.ToString();
                _process.Dispose();
                _process = null;
                throw new InvalidOperationException($"进程异常退出:\n{LastError}");
            }
            if (await HealthCheckAsync())
            {
                IsRunning = true;
                StateChanged?.Invoke();
                return;
            }
        }

        LastError = _outputBuffer.ToString();
        Stop();
        throw new InvalidOperationException($"启动超时 (20s):\n{LastError}");
    }

    public void Stop()
    {
        if (_process == null) return;
        IsRunning = false;

        try
        {
            if (!_process.HasExited)
            {
                _process.Kill();
                _process.WaitForExit(3000);
            }
            _process.Dispose();
        }
        catch { }
        finally { _process = null; }

        StateChanged?.Invoke();
    }

    private async Task<bool> HealthCheckAsync()
    {
        try
        {
            var res = await _http.GetAsync($"{BaseUrl}/api/health");
            return res.IsSuccessStatusCode;
        }
        catch { return false; }
    }
}