rokojori_action_library/Runtime/Math/Hexagon/HexagonCoord.cs

using Godot;
using System.Collections.Generic;

namespace Rokojori;


public struct HexagonCoord
{
  public readonly int q;
  public readonly int r;

  public HexagonCoord( int q, int r )
  {
    this.q = q;
    this.r = r;
  }

  public readonly static HexagonCoord Center = new HexagonCoord( 0, 0 );
  public HexagonCoord Middle => Center;

  public readonly static HexagonCoord East = new HexagonCoord( 1, 0 );
  public HexagonCoord Left => East;

  public readonly static HexagonCoord NorthEast = new HexagonCoord( 1, -1 );
  public HexagonCoord LeftUp => NorthEast;
  
  public readonly static HexagonCoord NorthWest = new HexagonCoord( 0, -1 );
  public HexagonCoord RightUp => NorthWest;    

  public readonly static HexagonCoord West = new HexagonCoord( -1, 0 );
  public HexagonCoord Right => West;    

  public readonly static HexagonCoord SouthWest = new HexagonCoord( -1, 1 );
  public HexagonCoord RightDown => SouthWest;   

  public readonly static HexagonCoord SouthEast = new HexagonCoord( 0, 1 );
  public HexagonCoord LeftDown => SouthEast;   


  static readonly HexagonCoord[] directions = new HexagonCoord[]
  {
    new HexagonCoord(  1,  0 ), 

    new HexagonCoord(  1, -1 ), 
    new HexagonCoord(  0, -1 ),

    new HexagonCoord( -1,  0 ), 
    new HexagonCoord( -1,  1 ), 
    new HexagonCoord(  0,  1 )
  };

  public static HexagonCoord Direction( int direction )
  {
    RJLog.Log( direction );
    return directions[ direction ];
  }

  public HexagonCoord Neighbor( int direction )
  {
    var d = directions[ direction ];
    return this + directions[ direction ]; 
  }

  public void ForEachNeighbor( System.Action<HexagonCoord> callback )
  {
    for ( int i = 0; i < directions.Length; i++ )
    {
      callback( Neighbor( i ) );
    }
  }

  public Vector3 ToWorldPosition( float size )
  {
    var x = size * 1.5f * q;
    var z = size * ( Mathf.Sqrt( 3f ) * 0.5f * q + Mathf.Sqrt( 3f ) * r );

    return new Vector3( x, 0, z );
  }

  public static HexagonCoord operator +(HexagonCoord a, HexagonCoord b)
  {
      return new HexagonCoord(
          a.q + b.q,
          a.r + b.r
      );
  }

  public static HexagonCoord operator -(HexagonCoord a, HexagonCoord b)
  {
      return new HexagonCoord(
          a.q - b.q,
          a.r - b.r
      );
  }

  public static HexagonCoord operator -(HexagonCoord a)
  {
      return new HexagonCoord(
          -a.q,
          -a.r
      );
  }

  public static HexagonCoord operator *(HexagonCoord a, int scalar)
  {
      return new HexagonCoord(
          a.q * scalar,
          a.r * scalar
      );
  }

  public static HexagonCoord operator *(int scalar, HexagonCoord a)
  {
      return a * scalar;
  }

  public static HexagonCoord operator /(HexagonCoord a, int scalar)
  {
      return new HexagonCoord(
          a.q / scalar,
          a.r / scalar
      );
  }

  public static bool operator ==(HexagonCoord a, HexagonCoord b)
  {
      return a.q == b.q && a.r == b.r;
  }

  public static bool operator !=(HexagonCoord a, HexagonCoord b)
  {
      return !(a == b);
  }

  public override bool Equals( object obj )
  {
    return obj is HexagonCoord other && other.q == q && other.r == r;
  }

  public override int GetHashCode()
  {
    return q * 397 ^ r;
  }

  public static List<HexagonCoord> Ring( int radius )
  {
    return Ring( HexagonCoord.Center, radius );
  }



  public static List<HexagonCoord> Ring( HexagonCoord center, int radius )
  {
    var results = new List<HexagonCoord>();

    if ( radius == 0 )
    {
      results.Add( center );
      return results;
    }

    var hex = center;

    for ( int i = 0; i < radius; i++ )
    {
      hex = hex.Neighbor( 4 );
    }

    for ( int side = 0; side < 6; side++ )
    {
      for ( int step = 0; step < radius; step++ )
      {
        results.Add( hex );
        hex = hex.Neighbor( side );
      }
    }

    return results;
  }
}