Square taken validations (#11)

closes #10

app/board.py

@@ -21,6 +21,9 @@
     ["A1", "B2", "C3"], # [3,5,7], # Diagonal DESC
 ]
 
+class SquareTakenError(ValueError):
+    pass
+
 class Board:
     def __init__(self):
         self.squares = [Square(square_name) for square_name in SQUARE_NAMES]
@@ -59,7 +62,9 @@ def get_squares(self, square_names):
 
     def set_square(self, square_name, player_letter):
         square = self.get_square(square_name)
-        if not square.letter:
+        if square.letter:
+            raise SquareTakenError(f"OOPS, square '{square_name}' already taken. please try again...")
+        else:
             square.letter = player_letter
 
 

app/game.py

@@ -1,7 +1,7 @@
 
 from itertools import cycle
 
-from app.board import Board
+from app.board import Board, SquareTakenError
 from app.player import select_player
 from app.move import Move
 
@@ -91,8 +91,11 @@ def play(self):
                     turn = (self.active_player.letter, square_name)
                     self.take_turn(turn)
                     break # break out of the input loop to conclude the turn and go to the next player
+                except SquareTakenError as err:
+                    print("...", err)
+                    next
                 except:
-                    print(f"OOPS UNRECOGNIZED SQUARE NAME '{square_name}'. PLEASE TRY AGAIN...")
+                    print(f"... OOPS UNRECOGNIZED SQUARE NAME '{square_name}'. PLEASE TRY AGAIN...")
                     next # ask the player for another input (this is only applicable for human players)
         print(self.board)
         print(self.outcome)