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

namespace gaemstone.ECS;

public unsafe class IdRef
	: IEquatable<IdRef>
{
	public World World { get; }
	public Id Id { get; }
	public IdFlags Flags => Id.Flags;

	public bool IsPair     => Id.IsPair;
	public bool IsWildcard => Id.IsWildcard;

	public bool IsValid => ecs_id_is_valid(World, this);
	public bool IsInUse => ecs_id_in_use(World, this);
	public int  Count   => ecs_count_id(World, this);

	public IdRef(World world, Id id)
		{ World = world; Id = id; }

	public static IdRef Combine(IdFlags flags, IdRef id)
		=> new(id.World, Id.Combine(flags, id));

	public static IdRef Pair(World world, Entity relation, Entity target)
		=> new(world, Id.Pair(relation, target));
	public static IdRef Pair(EntityRef relation, Entity target)
		=> Pair(relation.World, relation, target);
	public static IdRef Pair(Entity relation, EntityRef target)
		=> Pair(target.World, relation, target);
	public static IdRef Pair(EntityRef relation, EntityRef target)
		=> Pair(relation.World, relation, target);

	public EntityRef? AsEntity()
		=> (Flags == default) ? World.LookupAlive(new Entity(new() { Data = Id })) : null;
	public (EntityRef Relation, EntityRef Target)? AsPair()
		=> IsPair && (World.LookupAlive(Id.RelationUnsafe) is EntityRef relation) &&
		             (World.LookupAlive(Id.TargetUnsafe  ) is EntityRef target  )
			? (relation, target) : null;

	public bool Equals(IdRef? other) => (other is not null) && (World == other.World) && (Id == other.Id);
	public override bool Equals(object? obj) => Equals(obj as IdRef);
	public override int GetHashCode() => HashCode.Combine(World, Id);
	public override string? ToString() => ecs_id_str(World, this).FlecsToStringAndFree()!;

	public static bool operator ==(IdRef? left, IdRef? right) => ReferenceEquals(left, right) || (left?.Equals(right) ?? false);
	public static bool operator !=(IdRef? left, IdRef? right) => !(left == right);

	public static implicit operator Id(IdRef i) => i.Id;
	public static implicit operator ecs_id_t(IdRef i) => i.Id.Value;
}