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

namespace gaemstone.ECS;

public unsafe class IdentifierRef
	: IEquatable<IdentifierRef>
{
	public Universe Universe { get; }
	public Identifier ID { get; }

	public IdentifierFlags Flags => ID.Flags;
	public bool IsPair     => ID.IsPair;
	public bool IsWildcard => ID.IsWildcard;
	public bool IsValid    => ecs_id_is_valid(Universe, ID);

	public IdentifierRef(Universe universe, Identifier id)
		{ Universe = universe; ID = id; }

	public static IdentifierRef Combine(IdentifierFlags flags, IdentifierRef id)
		=> new(id.Universe, Identifier.Combine(flags, id));
	public static IdentifierRef Pair(EntityRef relation, Entity target)
		=> new(relation.Universe, Identifier.Pair(relation, target));
	public static IdentifierRef Pair(Entity relation, EntityRef target)
		=> new(target.Universe, Identifier.Pair(relation, target));

	public (EntityRef Relation, EntityRef Target)? AsPair()
		=> IsPair ? (Universe.LookupOrThrow(ID.RelationUnsafe), Universe.LookupOrThrow(ID.TargetUnsafe)) : null;

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

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

	public static implicit operator Identifier(IdentifierRef i) => i.ID;
	public static implicit operator ecs_id_t(IdentifierRef i) => i.ID.Value;
}