gaemstone/src/gaemstone/ECS/Query.cs

using System;
using gaemstone.Utility;
using static flecs_hub.flecs;

namespace gaemstone.ECS;

public unsafe sealed class Query
	: IDisposable
{
	public Universe Universe { get; }
	public ecs_query_t* Handle { get; }

	public Query(Universe universe, QueryDesc desc)
	{
		using var alloc = TempAllocator.Use();
		var flecsDesc = desc.ToFlecs(alloc);
		Universe = universe;
		Handle   = ecs_query_init(universe, &flecsDesc);
	}

	public void Dispose()
		=> ecs_query_fini(this);

	public Iterator Iter()
		=> new(Universe, IteratorType.Query, ecs_query_iter(Universe, this));

	public override string ToString()
		=> ecs_query_str(Handle).FlecsToStringAndFree()!;

	public static implicit operator ecs_query_t*(Query q) => q.Handle;
}

public class QueryDesc : FilterDesc
{
	public QueryDesc(string expression) : base(expression) {  }
	public QueryDesc(params Term[] terms) : base(terms) {  }

	public new unsafe ecs_query_desc_t ToFlecs(IAllocator allocator)
	{
		var desc = new ecs_query_desc_t {
			filter = base.ToFlecs(allocator),
			// TODO: Implement more Query features.
		};
		return desc;
	}
}