using System.Diagnostics;

namespace SinMaiLauncher.ChildProcessHolder;

internal abstract class ChildProcessStateBag(ChildProcessKind kind, IProcessStartInfo startInfo)
{
    public ChildProcessKind Kind { get; } = kind;

    public event EventHandler<EventArgs> StatusUpdated;

    private Process? process;
    public bool IsAlive => process?.HasExited == false;

    public int? Pid => process?.Id;

    public ChildProcessStatus Status
    {
        get;
        protected set
        {
            field = value;
            StatusUpdated?.Invoke(this, EventArgs.Empty);
        }
    }

    public async Task StartAsync()
    {
        if (process != null) throw new InvalidOperationException("Already started");

        Status = ChildProcessStatus.PreLaunching;

        if (false == Directory.Exists(startInfo.WorkingDir))
        {
            Status = ChildProcessStatus.MissingWorkingDir;
            return;
        }

        if (false == File.Exists(startInfo.Exe))
        {
            Status = ChildProcessStatus.MissingExeFile;
            return;
        }

        Status = ChildProcessStatus.Launching;

        process = Program.CreateConsoleProcess(startInfo);
        process.Exited += async delegate
        {
            process = null;
            Status = ChildProcessStatus.Stopped;
        };
        process.Start();

        if (IsAlive)
        {
            if (await CheckReadyAsync())
            {
                Status = ChildProcessStatus.Ready;
            }
            else
            {
                await StopAsync(TimeSpan.Zero);
            }
        }
    }

    protected virtual async Task<bool> CheckReadyAsync() => true;

    public virtual async Task StopAsync(TimeSpan timeout)
    {
        if (IsAlive) process!.Kill();
        Status = ChildProcessStatus.Stopped;
    }

    protected Task WaitForExitAsync() => IsAlive ? process!.WaitForExitAsync() : Task.CompletedTask;
    protected Task<bool> WaitForInputIdleAsync(TimeSpan timeout) => IsAlive ? Task.Run(() => process!.WaitForInputIdle(timeout)) : Task.FromResult(false);

    protected nint? MainWindowHWnd => IsAlive ? process!.MainWindowHandle : null;
    protected bool CloseMainForm() => IsAlive && process!.CloseMainWindow();

    protected void RefreshProcess() => process?.Refresh();
}