using System.Collections;
using System.Collections.Generic;
using gaemstone.ECS.Utility;
using static flecs_hub.flecs;

namespace gaemstone.ECS;

public unsafe readonly struct EntityType<TContext>
	: IReadOnlyList<Id<TContext>>
{
	public readonly World<TContext> World;
	public readonly ecs_type_t* Handle;

	public EntityType(World<TContext> world, ecs_type_t* handle)
		{ World = world; Handle = handle; }

	public override string ToString()
		=> ecs_type_str(World, Handle).FlecsToStringAndFree()!;

	// IReadOnlyList implementation
	public int Count => Handle->count;
	public Id<TContext> this[int index]
		=> Id<TContext>.GetUnsafe(World, new(Handle->array[index]));
	public IEnumerator<Id<TContext>> GetEnumerator()
		{ for (var i = 0; i < Count; i++) yield return this[i]; }
	IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}