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

namespace gaemstone.ECS;

public unsafe class Filter
	: IEnumerable<Iterator>
	, IDisposable
{
	public Universe Universe { get; }
	public ecs_filter_t* Handle { get; }

	private Filter(Universe universe, ecs_filter_t* handle)
		{ Universe = universe; Handle = handle; }

	public Filter(Universe universe, ecs_filter_desc_t desc)
		: this(universe, ecs_filter_init(universe, &desc)) {  }
	public Filter(Universe universe, string expression)
		: this(universe, new ecs_filter_desc_t { expr = expression }) {  }

	public static void RunOnce(Universe universe, Delegate action)
	{
		var gen = QueryActionGenerator.GetOrBuild(universe, action.Method);
		using var filter = new Filter(universe, gen.Filter);
		foreach (var iter in filter) gen.RunWithTryCatch(action.Target, iter);
	}

	~Filter() => Dispose();
	public void Dispose() { ecs_filter_fini(Handle); GC.SuppressFinalize(this); }

	public Iterator Iter() => new(Universe, IteratorType.Filter, ecs_filter_iter(Universe, this));
	public IEnumerator<Iterator> GetEnumerator() => Iter().GetEnumerator();
	IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

	public static implicit operator ecs_filter_t*(Filter q) => q.Handle;
}