using System;
using System.Diagnostics;
using System.IO;

namespace CommonwealthOnline.Host.Services;

// Launches the CommonwealthOnline.Server process, preferring a published
// apphost, then a framework-dependent DLL, then a source-tree dotnet run.
public sealed class ServerController
{
    private Process? _process;

    public bool IsRunning => _process is { HasExited: false };

    public event Action<string>? LogReceived;
    public event Action<bool>? RunningChanged;

    public void Start(string serverDir, string configPath)
    {
        if (IsRunning)
        {
            return;
        }

        var startInfo = ResolveLaunch(serverDir, configPath);
        var process = new Process { StartInfo = startInfo, EnableRaisingEvents = true };
        process.OutputDataReceived += (_, e) => Emit(e.Data);
        process.ErrorDataReceived += (_, e) => Emit(e.Data);
        process.Exited += (_, _) => RunningChanged?.Invoke(false);

        _process = process;
        process.Start();
        process.BeginOutputReadLine();
        process.BeginErrorReadLine();
        RunningChanged?.Invoke(true);
    }

    public void Stop()
    {
        if (_process is { HasExited: false } process)
        {
            try
            {
                process.Kill(entireProcessTree: true);
            }
            catch (Exception)
            {
                // Process already gone or not killable; RunningChanged fires on Exited.
            }
        }
    }

    private void Emit(string? line)
    {
        if (!string.IsNullOrEmpty(line))
        {
            LogReceived?.Invoke(line);
        }
    }

    private static ProcessStartInfo ResolveLaunch(string serverDir, string configPath)
    {
        var exeName = OperatingSystem.IsWindows()
            ? "CommonwealthOnline.Server.exe"
            : "CommonwealthOnline.Server";
        var apphost = Path.Combine(serverDir, exeName);
        var dll = Path.Combine(serverDir, "CommonwealthOnline.Server.dll");
        var project = Path.Combine(serverDir, "CommonwealthOnline.Server.csproj");

        var info = new ProcessStartInfo
        {
            WorkingDirectory = serverDir,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true,
        };

        if (File.Exists(apphost))
        {
            info.FileName = apphost;
            info.ArgumentList.Add("serve");
        }
        else if (File.Exists(dll))
        {
            info.FileName = "dotnet";
            info.ArgumentList.Add(dll);
            info.ArgumentList.Add("serve");
        }
        else
        {
            info.FileName = "dotnet";
            info.ArgumentList.Add("run");
            info.ArgumentList.Add("--project");
            info.ArgumentList.Add(project);
            info.ArgumentList.Add("-c");
            info.ArgumentList.Add("Release");
            info.ArgumentList.Add("--");
            info.ArgumentList.Add("serve");
        }

        info.ArgumentList.Add("--config");
        info.ArgumentList.Add(configPath);
        return info;
    }
}