using System;
using static flecs_hub.flecs;

namespace gaemstone.ECS;

public unsafe readonly struct Identifier
{
	public Universe Universe { get; }
	public ecs_id_t Value { get; }

    public bool IsPair => ecs_id_is_pair(Value);
	public IdentifierFlags Flags => (IdentifierFlags)(Value.Data & ECS_ID_FLAGS_MASK);

	public Identifier(Universe universe, ecs_id_t value)
		{ Universe = universe; Value = value; }

	public static Identifier Pair(Entity first, Entity second)
		=> new(first.Universe, Universe.ECS_PAIR | ((first.Value.Data << 32) + (uint)second.Value.Data));
	public static Identifier Pair(ecs_entity_t first, Entity second)
		=> new(second.Universe, Universe.ECS_PAIR | ((first.Data << 32) + (uint)second.Value.Data));

	public (Entity, Entity) AsPair()
		=> (Universe.Lookup((ecs_id_t)((Value & ECS_COMPONENT_MASK) >> 32)),
		    Universe.Lookup((ecs_id_t)(Value & ECS_ENTITY_MASK)));

    // public Entity AsComponent()
    // {
    //     var value = Value.Data & ECS_COMPONENT_MASK;
    //     return new Entity(Universe, new() { Data = value });
    // }

    public override string ToString()
		=> ecs_id_str(Universe, Value).ToStringAndFree();


	public static implicit operator ecs_id_t(Identifier e) => e.Value;

	public static Identifier operator |(ecs_id_t left, Identifier right)
		=> new(right.Universe, left | right.Value);
	public static Identifier operator |(Identifier left, Identifier right)
		=> new(left.Universe, left.Value | right.Value);
}

[Flags]
public enum IdentifierFlags : ulong
{
	Pair     = 1ul << 63,
	Override = 1ul << 62,
	Toggle   = 1ul << 61,
	Or       = 1ul << 60,
	And      = 1ul << 59,
	Not      = 1ul << 58,
}