Comments to not forget how to check checkmate

chess/board.go

@@ -46,10 +46,31 @@ func (b Board) GetPieceAt(coord types.Coordinate) (types.Piece, bool) {
 	return piece, found
 }
 func (b *Board) CheckMove(move types.Move) (bool, string) {
-	_, found := b.GetPieceAt(move.StartSquare)
+	pieceAtStartSquare, found := b.GetPieceAt(move.StartSquare)
 	if !found {
 		return false, "no piece at start square"
 	}
 
+    pieceAtEndSquare, found := b.GetPieceAt(move.EndSquare)
+    if found {
+        if pieceAtEndSquare.Color == pieceAtStartSquare.Color {
+            return false, "same-coloured piece at end square"
+        }
+    }
+
+    //Check if king of moving color is in check -> move not allowed
+    //Do that by checking if the king is in a square attacked by the other color.
+
+    //Check for checkmate
+    //Is every square that the king can move to attacked? And can no other
+    //piece block? -> checkmate
+
+    //Maybe for checking checkmate, we have to check the 'path' in which the
+    //checkmate is given
+
+    // |K| | | | |Q|
+    // in this scenaria the path are all the squares between queen and king.
+    // If a piece can be moved into the path, it is no checkmate
+
 	return true, ""
 }