using System;
using System.Runtime.CompilerServices;
using gaemstone.ECS.Utility;
using static flecs_hub.flecs;

namespace gaemstone.ECS;

public unsafe partial struct Entity<TContext>
{
	public Entity<TContext> InitComponent<T>()
	{
		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 = typeof(T).IsValueType ? Unsafe.SizeOf<T>() : sizeof(ReferenceHandle);
		var typeInfo = new ecs_type_info_t { size = size, alignment = size };
		var componentDesc = new ecs_component_desc_t { entity = this, type = typeInfo };
		ecs_component_init(World, &componentDesc);

		if (!typeof(T).IsValueType) {
			// Set up component hooks for proper freeing of GCHandles.
			// Without them, managed classes would never be garbage collected.
			var typeHooks = new ecs_type_hooks_t {
				ctor = new() { Data = new() { Pointer = &ReferenceHandle.Construct } },
				dtor = new() { Data = new() { Pointer = &ReferenceHandle.Destruct } },
				move = new() { Data = new() { Pointer = &ReferenceHandle.Move } },
				copy = new() { Data = new() { Pointer = &ReferenceHandle.Copy } },
			};
			ecs_set_hooks_id(World, this, &typeHooks);
		}

		return CreateLookup<T>();
	}
}