1 from nose.tools import assert_equals
   2 
   3 def legal_moves(board, player):
   4     """
   5     Given a board encoded as a list of strings and a player char
   6     returns pairs identifying positions of legal moves for given player
   7     and given situation on the board.
   8     """
   9     all_directions = [(-1, -1), (-1, 0), (-1, 1),
  10                       (0, -1),           (0, 1),
  11                       (1, -1),  (1, 0),  (1, 1)]
  12     moves = []
  13     for pos in find_pieces(board, player):
  14         for direction in all_directions:
  15             new_move = check_direction(board, pos, direction)
  16             if new_move is not None:
  17                 moves.append(new_move)
  18     return moves
  19 
  20 def find_pieces(board, player):
  21     """ find all coords for the player piece. """
  22     coords = []
  23     for i in range(len(board)):
  24         for j in range(len(board)):
  25             if board[i][j] == player:
  26                 coords.append((i, j))
  27     return coords
  28 
  29 def check_direction(board, start, direction):
  30     enemy = {"b": "w", "w": "b"}
  31     row, col = start
  32     delta_r, delta_c = direction
  33     found_enemy = False
  34     player = board[start[0]][start[1]]
  35     while True:
  36         row, col = row + delta_r, col + delta_c
  37         if row >= len(board) or col >= len(board[0]):
  38             return None
  39         if board[row][col] == enemy[player]:
  40             found_enemy = True
  41         if board[row][col] == '.' and found_enemy:
  42             return (row, col)
  43         if board[row][col] == '.' and not found_enemy:
  44             return None
  45         if board[row][col] == player:
  46             return None
  47 
  48 TEST_BOARD = ["....",
  49               ".bw.",
  50               ".wb.",
  51               "...."]
  52 
  53 def test_simple():
  54     assert_equals(legal_moves(TEST_BOARD, 'w'), [(1, 0), (3, 2), (0, 1), (2, 3)])
  55 
  56 def test_find_pieces():
  57     assert_equals(find_pieces(TEST_BOARD, 'b'), [(1, 1), (2, 2)],
  58         find_pieces(TEST_BOARD, 'b'))
  59 
  60 def test_check_direction():
  61     assert_equals(check_direction(TEST_BOARD, (1, 1), (0, 1)), (1, 3))
  62     assert_equals(check_direction(TEST_BOARD, (1, 1), (-1, 0)), None)
  63     assert_equals(check_direction(TEST_BOARD, (1, 1), (0, 0)), None)
  64 
  65 TEST_BOARD2 = ['bww']
  66 
  67 def test_check_border():
  68     assert_equals(check_direction(TEST_BOARD2, (0,0), (0, 1)), None)