using Android.App;
using Android.Content;
using Android.Graphics;
using Android.OS;
using Android.Runtime;
using Android.Views;
using StereoKit;
using System;
using System.Reflection;
using System.Threading;

namespace slash;

[Activity(Label = "@string/app_name", MainLauncher = true, Exported = true)]
[IntentFilter(new[] { Intent.ActionMain }, Categories = new[] { "org.khronos.openxr.intent.category.IMMERSIVE_HMD", "com.oculus.intent.category.VR", Intent.CategoryLauncher })]
public class MainActivity : Activity, ISurfaceHolderCallback2
{
    View surface;

    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        Run();
        SetContentView(Resource.Layout.activity_main);
    }

    protected override void OnDestroy()
    {
        SK.Quit();
        base.OnDestroy();
    }

    static bool running = false;
    void Run()
    {
        if (running) return;
        running = true;

        // Before anything else, give StereoKit the Activity. This should
        // be set before any other SK calls, otherwise native library
        // loading may fail.
        SK.AndroidActivity = this;

        // Set up a surface for StereoKit to draw on, this is only really
        // important for flatscreen experiences.
        Window.TakeSurface(this);
        Window.SetFormat(Format.Unknown);
        surface = new View(this);
        SetContentView(surface);
        surface.RequestFocus();

        // Task.Run will eat exceptions, but Thread.Start doesn't seem to.
        new Thread(InvokeStereoKit).Start();
    }

    static void InvokeStereoKit()
    {
        Type entryClass = typeof(Program);
        MethodInfo entryPoint = entryClass?.GetMethod("Main", BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic);

        // There are a number of potential method signatures for Main, so
        // we need to check each one, and give it the correct values.
        //
        // Converting MethodInfo into an Action instead of calling Invoke on
        // it allows for exceptions to properly bubble up to the IDE.
        ParameterInfo[] entryParams = entryPoint?.GetParameters();
        if (entryParams == null || entryParams.Length == 0)
        {
            Action Program_Main = (Action)Delegate.CreateDelegate(typeof(Action), entryPoint);
            Program_Main();
        }
        else if (entryParams?.Length == 1 && entryParams[0].ParameterType == typeof(string[]))
        {
            Action<string[]> Program_Main = (Action<string[]>)Delegate.CreateDelegate(typeof(Action<string[]>), entryPoint);
            Program_Main(new string[] { });
        }
        else throw new Exception("Couldn't invoke Program.Main!");

        Process.KillProcess(Process.MyPid());
    }

    // Events related to surface state changes
    public void SurfaceChanged(ISurfaceHolder holder, [GeneratedEnum] Format format, int width, int height) => SK.SetWindow(holder.Surface.Handle);
    public void SurfaceCreated(ISurfaceHolder holder) => SK.SetWindow(holder.Surface.Handle);
    public void SurfaceDestroyed(ISurfaceHolder holder) => SK.SetWindow(IntPtr.Zero);
    public void SurfaceRedrawNeeded(ISurfaceHolder holder) { }
}