namespace Theater_ECS;

using System;
using System.Threading;
using System.Collections;

class ComponentManager
{
	private Monitor _Lock = new .() ~ delete _;

	private int_cosize _ComponentSize = -1;
	private readonly int _IndexSize = sizeof(int_cosize);

	private int_cosize _Next = 0;
	private List<uint8> _Data = null ~ delete _;
	private List<int_cosize> _Available = new .() ~ delete _;
	private HashSet<int_cosize> _Deleted = new .() ~ delete _;

	///Make the component manager useable for a specific type of component
	public void Initialize<T>(int_cosize count) where T : struct
	{
		_ComponentSize = sizeof(T);
		_Data = new .( //So that we dont have to realloc as frequently
			(_IndexSize + _ComponentSize) * count
			);
	}

	///Creates space for a new component instance and returns a pointer to it
	public (Component, void*) Create(Entity owner)
	{
		if (_Available.Count > 0)
		{
			var idx = _Available.PopFront();
			_Deleted.Remove(idx);

			*(int_cosize*)(void*)&_Data[idx * (_ComponentSize + _IndexSize)] = owner;
			void* toReturn = (void*)&_Data[idx * (_ComponentSize + _IndexSize) + _IndexSize];
			return (
				idx,
				toReturn
				);
		}
		else
		{
			Grow();
			*(int_cosize*)(void*)(_Data.Ptr + (_Next * (_ComponentSize + _IndexSize))) = owner;
			//This calculates to the next biggest position + the offset of the index
			void* toReturn = (void*)(_Data.Ptr + (_Next * (_ComponentSize + _IndexSize) + _IndexSize));
			return (
				_Next++,
				toReturn
				);
		}
	}

	///Remove an entry, and returns a pointer to the removed object, if you want to
	public Result<void*> Remove(int_cosize idx)
	{
		if (idx >= _Next || _Deleted.Contains(idx))
			return .Err;

		*(int_cosize*)(void*)&_Data[idx * (_ComponentSize + _IndexSize)] = -1;

		_Deleted.Add(idx);

		return .Ok(
			(void*)(_Data.Ptr + idx * (_ComponentSize + _IndexSize) + _IndexSize)
			);
	}

	public int_cosize Count
	{
		get
		{
			return (.)(_Data.Count / (_ComponentSize + _IndexSize));
		}
	}


	public Span<(Entity, T)> GetAll<T>() where T : struct
	{
		return .((.)(void*)_Data.Ptr, Count);
	}

	[Unchecked]
	public T* Get<T>(int_cosize idx) where T : struct
	{
		return (T*)(void*)(_Data.Ptr + idx * (_ComponentSize + _IndexSize) + _IndexSize);
	}

	[Unchecked]
	public void GetEntities(List<Entity> list)
	{
		var ec = (_Data.Count / (_ComponentSize + _IndexSize));
		list.GrowUninitialized(ec);
		for (int i < ec)
			*(list.Ptr + (i)) = *(Entity*)(void*)(_Data.Ptr +i * (_ComponentSize + _IndexSize));
	}

	public void Use() => _Lock.Enter();
	public void StopUsing() => _Lock.Exit();


	public void Grow(int_cosize amount = 1)
	{ //Make more size useable
		_Data.GrowUninitialized((_ComponentSize + _IndexSize) * amount);
	}

}