using System;
using System.Runtime.CompilerServices;
using static flecs_hub.flecs;

namespace gaemstone.ECS;

public static class ComponentExtensions
{
	public unsafe static EntityRef InitComponent(this EntityRef entity, Type type)
		=> (EntityRef)typeof(ComponentExtensions)
			.GetMethod(nameof(InitComponent), new[] { typeof(EntityRef) })!
			.MakeGenericMethod(type).Invoke(null, new[]{ entity })!;

	public unsafe static EntityRef InitComponent<T>(this EntityRef entity)
	{
		if (typeof(T).IsPrimitive) throw new ArgumentException(
			"Must not be primitive");
		if (typeof(T).IsValueType && RuntimeHelpers.IsReferenceOrContainsReferences<T>()) throw new ArgumentException(
			"Struct component must satisfy the unmanaged constraint. " +
			"Consider making it a class if you need to store references.");

		var size = Unsafe.SizeOf<T>();
		var typeInfo = new ecs_type_info_t
			{ size = size, alignment = size };
		var componentDesc = new ecs_component_desc_t
			{ entity = entity, type = typeInfo };
		ecs_component_init(entity.World, &componentDesc);
		return entity.CreateLookup(typeof(T));
	}
}