using System;
using static flecs_hub.flecs;

namespace gaemstone.ECS;

public readonly struct Identifier
	: IEquatable<Identifier>
{
	public readonly ecs_id_t Value;

	public bool IsPair     => ecs_id_is_pair(Value);
	public bool IsWildcard => ecs_id_is_wildcard(Value);

	public IdentifierFlags Flags => (IdentifierFlags)(Value & ECS_ID_FLAGS_MASK);

	public Entity RelationUnsafe => new(new() { Data = (Value & ECS_COMPONENT_MASK) >> 32 });
	public Entity TargetUnsafe   => new(new() { Data =  Value & ECS_ENTITY_MASK });

	public Identifier(ecs_id_t value) => Value = value;

	public static Identifier Combine(IdentifierFlags flags, Identifier id)
		=> new((ulong)flags | id.Value);

	public static Identifier Pair(Entity relation, Entity target)
		=> Combine(IdentifierFlags.Pair, new(
			((relation.Value.Data << 32) & ECS_COMPONENT_MASK) |
			(   target.Value.Data        & ECS_ENTITY_MASK   )));

	public (EntityRef Relation, EntityRef Target)? AsPair(Universe universe)
		=> new IdentifierRef(universe, this).AsPair();

	public bool Equals(Identifier other) => Value.Data == other.Value.Data;
	public override bool Equals(object? obj) => (obj is Identifier other) && Equals(other);
	public override int GetHashCode() => Value.Data.GetHashCode();
	public override string? ToString()
		=> (Flags != default) ? $"Identifier(0x{Value.Data:X}, Flags={Flags})"
		                      : $"Identifier(0x{Value.Data:X})";

	public static bool operator ==(Identifier left, Identifier right) =>  left.Equals(right);
	public static bool operator !=(Identifier left, Identifier right) => !left.Equals(right);

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

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