Added IDA* control step

Added flow control to find start+destination points,
and increase the threshold if a search doesn't reach the destination.

Next step: implement search.

IDAstar.cs

@@ -1,7 +1,7 @@
 using System.Collections.ObjectModel;
-using System.Threading.Channels;
 
-namespace IdaStar {
+namespace IdaStar
+{
 
 	public enum CellState {
         EMPTY,
@@ -41,6 +41,12 @@ namespace IdaStar {
 		}
     }
 
+	public record struct Point(int Row, int Column) {
+        public int ManhattanDistance(Point otherPoint) {
+			return Math.Abs(Row - otherPoint.Row) + Math.Abs(Column - otherPoint.Column);
+		}
+    }
+
 	public class WorkingBoard {
 		readonly List<List<CellState>> _board;
 
@@ -65,11 +71,74 @@ namespace IdaStar {
 
 		public event Action<WorkingBoard>? AlgorithmStep;
 
-		public void RunIdaStar() {
+        /// <summary>
+		/// Clean board, making it ready for a new run.
+        /// 
+		/// This is achieved by setting all PATH states to EMPTY states.
+		/// </summary>
+        public void Reset() {
+            foreach (var row in _board) {
+				for (var i = 0; i < row.Count; i++) {
+                    if (row[i] == CellState.PATH) {
+						row[i] = CellState.EMPTY;
+					}
+				}
+			}
+        }
+
+		public void RunIdaStar() => RunIdaStar(0, 1, (p1, p2) => p1.ManhattanDistance(p2));
+		public void RunIdaStar<Comp>(Comp zero, Comp increment, Func<Point, Point, Comp> heuristic) where Comp: IComparable<Comp> {
+			// Don't run algorithm on a "dirty" board
+			// "dirty" = the algorithm was already ran before
+			if (_board.Select((row) => row.Where((state) => state == CellState.PATH).Count()).Any((cnt) => cnt > 0)) {
+				throw new DirtyBoardException();
+			}
+
+            Point findPoint(CellState neededState) {
+                for (var i = 0; i < _board.Count; i++) {
+                    for (var j = 0; j < _board[i].Count; j++) {
+                        if (_board[i][j] == CellState.START) {
+                            return new(i, j);
+                        }
+                    }
+                }
+                throw new NoPoint(neededState);
+            }
+
+			Point startPoint = findPoint(CellState.START);
+
+			Point destinationPoint = findPoint(CellState.DESTINATION);
+
+            Comp search(Point current, Comp cost, Comp threshold) {
 				throw new NotImplementedException();
 			}
+
+			var threshold = heuristic(startPoint, destinationPoint);
+            while (threshold.CompareTo(zero) == 0) {
+				threshold = search(startPoint, zero, threshold);
+			}
+		}
+    }
+
+    [System.Serializable]
+    public class DirtyBoardException : System.Exception
+    {
+        public DirtyBoardException() : base("The board is dirty (contains path cells)") { }
+        public DirtyBoardException(System.Exception inner) : base("The board is dirty (contains path cells)", inner) { }
+        protected DirtyBoardException(
+            System.Runtime.Serialization.SerializationInfo info,
+            System.Runtime.Serialization.StreamingContext context) : base(info, context) { }
     }
 
+    [System.Serializable]
+    public class NoPoint : System.Exception
+    {
+        public NoPoint(CellState neededState) : base($"The board doesn't contain any {neededState} point") { }
+        public NoPoint(CellState neededState, System.Exception inner) : base($"The board doesn't contain any {neededState} point", inner) { }
+        protected NoPoint(
+            System.Runtime.Serialization.SerializationInfo info,
+            System.Runtime.Serialization.StreamingContext context) : base(info, context) { }
+    }
 }
 
 /*