using System;
using System.Collections.Generic;
using System.Numerics;
using System.Runtime.InteropServices;

namespace Ougge;

[StructLayout(LayoutKind.Sequential)]
public struct Transform
{
    Vector2 scale;  
    Vector2 position;
    float rotation;
}

public class GameObject
{
    // index in GameObjectPool
    private ulong _id;
    private uint _index;
    private bool _isDestroyed;

    public ulong Id => _id;
    public bool IsDestroyed => _isDestroyed;

    public Transform Transform { get; }
    public GameObject? Parent;

    public Dictionary<Type, Component> Components;

    private GameObject(ulong id, uint nativePoolIndex)
    {
        _id = id;
        _index = nativePoolIndex;
        // Do not move this line or mono runtime will throw SEGFAULT.
        // Mono runtime can't set values in field declaration, but initializing everything in constructor is OK. 
        Components = new();
    }

    static public GameObject Create()
    {
        NativeMethods.createGameObject(out ulong id, out uint index);
        var o = new GameObject(id, index);
        return o;
    }

    public void Destroy()
    {
        if(_isDestroyed)
            return;

        _isDestroyed = NativeMethods.destroyGameObject(_index);
        if(!_isDestroyed)
            throw new Exception($"Can't destroy GameObject({_id})");
    }

    /// <param name="t">type derived from Component</param>
    /// <returns>true if new component instance was created, false if component of the same tipe is already added to GameObject</returns>
    /// <exception cref="Exception"></exception>
    public bool TryCreateComponent(Type t)
    {
        if(!t.IsSubclassOf(typeof(Component)))
            throw new Exception($"type {t.FullName} is not a derived class of {typeof(Component).FullName}");

        if(Components.ContainsKey(t))
            return false;
        
        Components.Add(t, (Component)Activator.CreateInstance(t, this));
        return true;
    }
    private bool TryCreateComponent_internal(string fullName)
    {
        Type t = Type.GetType(fullName) ?? throw new Exception($"type not found '{fullName}'");
        return TryCreateComponent(t);
    }
    
    private void InvokeUpdate(double deltaTime)
    {
        foreach(var p in Components)
        {
            p.Value.Update(deltaTime);
        }
    }
}