using System;
using System.Collections.Immutable;
using System.Numerics;

namespace gaemstone.Bloxel;

public enum BlockFacing
{
	East,  // +X
	West,  // -X
	Up,    // +Y
	Down,  // -Y
	South, // +Z
	North, // -Z
}

public static class BlockFacings
{
	public static readonly ImmutableHashSet<BlockFacing> Horizontals
		= ImmutableHashSet.Create(BlockFacing.East , BlockFacing.West ,
		                          BlockFacing.South, BlockFacing.North);

	public static readonly ImmutableHashSet<BlockFacing> Verticals
		= ImmutableHashSet.Create(BlockFacing.Up, BlockFacing.Down);

	public static readonly ImmutableHashSet<BlockFacing> All
		= Horizontals.Union(Verticals);
}

public static class BlockFacingExtensions
{
	public static void Deconstruct(this BlockFacing self, out int x, out int y, out int z)
		=> (x, y, z) = self switch {
			BlockFacing.East  => (+1,  0,  0),
			BlockFacing.West  => (-1,  0,  0),
			BlockFacing.Up    => ( 0, +1,  0),
			BlockFacing.Down  => ( 0, -1,  0),
			BlockFacing.South => ( 0,  0, +1),
			BlockFacing.North => ( 0,  0, -1),
			_ => throw new ArgumentException(
				$"'{self}' is not a valid BlockFacing", nameof(self))
		};

	public static bool IsValid(this BlockFacing self)
		=> (self >= BlockFacing.East) && (self <= BlockFacing.North);

	public static BlockFacing GetOpposite(this BlockFacing self)
		=> (BlockFacing)((int)self ^ 0b1);

	public static Vector3 ToVector3(this BlockFacing self)
		=> self switch {
			BlockFacing.East  =>  Vector3.UnitX,
			BlockFacing.West  => -Vector3.UnitX,
			BlockFacing.Up    =>  Vector3.UnitY,
			BlockFacing.Down  => -Vector3.UnitY,
			BlockFacing.South =>  Vector3.UnitZ,
			BlockFacing.North => -Vector3.UnitZ,
			_ => throw new ArgumentException(
				$"'{self}' is not a valid BlockFacing", nameof(self))
		};
}