Organize domain project.

Shogi.Domain/YetToBeAssimilatedIntoDDD/Pathing/Direction.cs

@@ -0,0 +1,22 @@
+using System.Numerics;
+
+namespace Shogi.Domain.YetToBeAssimilatedIntoDDD.Pathing
+{
+    /// <summary>
+    /// Directions are relative to the perspective of Player 1.
+    /// Up points towards player 1. Down points towards player 2.
+    /// </summary>
+    public static class Direction
+    {
+        public static readonly Vector2 Up = new(0, 1);
+        public static readonly Vector2 Down = new(0, -1);
+        public static readonly Vector2 Left = new(-1, 0);
+        public static readonly Vector2 Right = new(1, 0);
+        public static readonly Vector2 UpLeft = new(-1, 1);
+        public static readonly Vector2 UpRight = new(1, 1);
+        public static readonly Vector2 DownLeft = new(-1, -1);
+        public static readonly Vector2 DownRight = new(1, -1);
+        public static readonly Vector2 KnightLeft = new(-1, 2);
+        public static readonly Vector2 KnightRight = new(1, 2);
+    }
+}

Shogi.Domain/YetToBeAssimilatedIntoDDD/Pathing/Distance.cs

@@ -0,0 +1,8 @@
+namespace Shogi.Domain.YetToBeAssimilatedIntoDDD.Pathing
+{
+    public enum Distance
+    {
+        OneStep,
+        MultiStep
+    }
+}

Shogi.Domain/YetToBeAssimilatedIntoDDD/Pathing/Path.cs

@@ -0,0 +1,41 @@
+using System.Diagnostics;
+
+namespace Shogi.Domain.YetToBeAssimilatedIntoDDD.Pathing
+{
+    [DebuggerDisplay("{Direction} - {Distance}")]
+    public class Path
+    {
+        public Vector2 Direction { get; }
+        public Distance Distance { get; }
+        public Path(Vector2 direction, Distance distance = Distance.OneStep)
+        {
+            Direction = direction;
+            Distance = distance;
+        }
+
+        public Path Invert() => new(Vector2.Negate(Direction), Distance);
+    }
+
+    public static class PathExtensions
+    {
+        public static Path GetNearestPath(this IEnumerable<Path> paths, Vector2 start, Vector2 end)
+        {
+            if (!paths.DefaultIfEmpty().Any())
+            {
+                throw new ArgumentException("No paths to get nearest path from.");
+            }
+
+            var shortestPath = paths.First();
+            foreach (var path in paths.Skip(1))
+            {
+                var distance = Vector2.Distance(start + path.Direction, end);
+                var shortestDistance = Vector2.Distance(start + shortestPath.Direction, end);
+                if (distance < shortestDistance)
+                {
+                    shortestPath = path;
+                }
+            }
+            return shortestPath;
+        }
+    }
+}