board.py

import numpy as np
from utils import log


class Board(object):
    """
    The environment for the reinforcement learning project.

    It should:
        - Have a matrix of size = NxN (which is basically N rows and N columns where N is a positive integer, greater than 0)
            - I have taken N as 3, but that is not necessary.
        - Initialize the matrix with zeroes.
            - The values in the matrix will be represented by integers: 0, 1, 2.
                - 0: empty cell represented by ' '.
                - 1: cell occupied by symbol 'O'.
                - 2: cell occupied by symbol 'X'.
            - 'X' or 'O' can be chosen by the player at initialization step by providing a choice in `player_sym`, defaults to 'x'
            - The other symbol will be chosen for the bot.
        - Have a property of winner, initialized by None.
        - Have a method to reset the board.
        - Have a method to represent the board in a human friendly form using 'X', 'O' and ' ' instead of the respective integers 2, 1, and 0.
        - Have a method which lets a user play by plotting a symbol of 'X' or 'O' only! anywhere within the matrix.
        - Calculates if there is a winner after each symbol is plotted.
            - A win is defined by any row, column or diagonal being filled with the same symbol, with the symbol as the winner.
        - If there is a winner, prints a message for the same.
    """
    def __init__(self, n=3, player_sym='x'):
        """
        Constructor of the Board class, creates board objects.

        - n(default=3) int: The number of rows and columns in the tic-tac-toe board.
        - player_sym(default='x') str: The symbol chosen by a human player.
        """
        self.board = None
        self.reset_board(n)
        self.stale = False
        # Initalize the board

        self.sym_o = {
            'mark': 'O',
            'value': 1
        }
        # Setup the 'O' symbol

        self.sym_x = {
            'mark': 'X',
            'value': 2
        }
        # Setup the 'X' symbol

        self.sym_empty = {
            'mark': ' ',
            'value': 0
        }
        # Setup the default ' ' Symbol

        self.player_sym, self.bot_sym = (self.sym_x, self.sym_o) \
                                        if player_sym.lower() == 'x' \
                                        else (self.sym_o, self.sym_x)
        # Ensure different symbols are assigned to the bot and the player.

        self.winner = None
        # Initialize the winner as None

    def reset_board(self, n=3):
        """
        params:

        - n(default=3): int: The number of rows and columns in the tic-tac-toe board.
        Clear the board when the game is to be restarted or a new game has to be started.
        """
        self.board = np.zeros((n, n)).astype(int)
        self.winner = None

    def draw_char_for_item(self, item):
        """
        Returns the string mapping of the integers in the matrix
        which can be understood by, but is not equal to:
        {
            0: ' ',
            1: 'O',
            2: 'X'
        }
        (The exact mapping is present in the constructor)

        params:

        - item int: One of (1, 2, 0) representing the mark of the player, bot or empty.
        return: str
        """
        if item == self.sym_x.get('value'):
            # If item = 2 (value of symbol x, return mark of symbol x viz: 'X')
            return self.sym_x.get('mark')
        elif item == self.sym_o.get('value'):
            # If item = 1 (value of symbol o, return mark of symbol o viz: 'O')
            return self.sym_o.get('mark')
        else:
            # Otherwise the cell must be empty, as only 1, 2 have 'O','X' mapped onto them.
            return self.sym_empty.get('mark')

    def draw_board(self):
        """
        Prints a human friendly representation of the tic-tac-toe board
        """
        elements_in_board = self.board.size
        # Calculate the elements in the board

        items = [
            self.draw_char_for_item(self.board.item(item_idx))
            for item_idx in range(elements_in_board)
        ]
        # For each integer cell/element in the matrix, find the character mapped to it
        # and store in a list.
        board = """
             {} | {} | {}
            -----------
             {} | {} | {}
            -----------
             {} | {} | {}
        """.format(*items)
        # The *items expand to N arguments where N is the number of elements in `items`,
        # which is equal to the number of elements in the matrix, hence the string equivalent
        # of the board
        print(board)

    def have_same_val(self, axis, item, item_x, item_y):
        """
        Oh boy! without the documentation this would be just 12-14 lines of code.

        Checks if a row(if axis = 0) of the board matrix has same values throughout.
                                    or
        Checks if a column(if axis = 1) of the board matrix has same values throughout.

        This is useful to check if a row or column is filled up by the symbol which was added the latest.

        params:

        - axis int: The direction along which operations are to be performed. Can have a value of 0 or 1 only.
            - 0 means row
            - 1 means column
        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        - item int: The latest integer inserted into the matrix at row-index = item_x, and column-index = item_y.
        """
        max_limit, _ = self.board.shape
        # Get the number of rows in the board.

        result = True
        # Optimistic approach, assume the result to be true,
        # unless proven wrong in the further steps.

        row_idx = col_idx = 0
        # set row_idx and col_idx iteration variables as 0
        # they don't get used much, they are present for code readability.

        main_idx, fixed_idx, ignore_idx = (col_idx, item_x, item_y) \
                                            if axis == 0 \
                                            else (row_idx, item_y, item_x)
        # main_idx: Update this index each iteration of the loop.
        # fixed_idx: Don't modify this index ever.
        # ignore_idx: this is the index of the inserted element
        #              which doesn't need to be evaluated, so ignore.
        # The if-else ensures weather to increment the row index
        # or the column index according to the value of the axis.

        while main_idx < max_limit:
            # If the main_idx which starts at 0 is less than number of rows/cols in matrix.
            if main_idx != ignore_idx:
                # And main_idx is not equal to the index of the latest item inserted (ignore_idx)
                # because for a fixed_index if we compare main_idx and ignore_idx it would give us the
                # latest element added, which will be equal to itself.
                # Learning algorithms are costly, ain't nobady got time fo that!

                board_item = self.board[fixed_idx][main_idx] \
                    if axis == 0 \
                    else self.board[main_idx][fixed_idx]
                # find the item(board_item) in the matrix
                # corresponding to main_idx and the fixed_index.
                # It should be an element in the same row or column depending on the axis.

                if board_item != item or board_item == 0:
                    # If the board_item found is not equal to the latest item added
                    # or if the board item is 0, which is still not marked by bot or player,
                    # result is false as the function didn't find all
                    # values to be same across the row, or column.
                    # and exit the loop because a single-mismatch is sufficient
                    # to confirm that all elements are not same.
                    result = False
                    break
            main_idx += 1
        return result

    def left_diagonal_has_same_values(self, item, item_x, item_y):
        """
        params

        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        - item int: The latest integer inserted into the matrix at row-index = item_x, and column-index = item_y.
        """
        i = j = 0
        # set i, j to 0

        result = True
        # Optimistic approach, assume the result to be true,
        # unless proven wrong in the further steps.

        max_limit, _ = self.board.shape
        # Get the number of rows in the board.

        while i < max_limit:
            # The row index i is sufficient as i and j are incremented
            # by same factor resulting in same values (Either would do)
            if i != item_x:
                # Avoid checking for the latest item added as that's what we are comparing with
                if self.board[i][j] != item or self.board[i][j] == 0:
                    # If the board_item found is not equal to the latest item added
                    # result is false as the function didn't find all
                    # values to be same across the row, or column.
                    # and exit the loop because a single-mismatch is sufficient
                    # to confirm that all elements are not same.
                    result = False
                    break
            i += 1
            j += 1
        return result

    def right_diagonal_has_same_values(self, item, item_x, item_y):
        """
        params

        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        - item int: The latest integer inserted into the matrix at row-index = item_x, and column-index = item_y.
        """
        result = True
        max_limit, _ = self.board.shape
        i = 0
        j = max_limit - 1
        while i < max_limit:
            # The row index i is sufficient as i and j are incremented
            # by same factor resulting in same values (Either would do)
            if i != item_x:
                # Avoid checking for the latest item added as that's what we are comparing with
                if self.board[i][j] != item or self.board[i][j] == 0:
                    # If the board_item found is not equal to the latest item added
                    # result is false as the function didn't find all
                    # values to be same across the row, or column.
                    # and exit the loop because a single-mismatch is sufficient
                    # to confirm that all elements are not same.
                    result = False
                    break
            i += 1
            j -= 1
        return result

    def cols_have_same_values(self, item, item_x, item_y):
        """
        Check if any of the columns have same values

        params

        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        - item int: The latest integer inserted into the matrix at row-index = item_x, and column-index = item_y.
        """
        axis = 1
        return self.have_same_val(axis, item, item_x, item_y)

    def rows_have_same_values(self, item, item_x, item_y):
        """
        Check if any of the rows have same values

        params

        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        - item int: The latest integer inserted into the matrix at row-index = item_x, and column-index = item_y.
        """
        axis = 0
        return self.have_same_val(axis, item, item_x, item_y)

    def element_diagonal_has_same_value(self, item, item_x, item_y):
        """
        Check if any of the diagonals have same values

        params

        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        - item int: The latest integer inserted into the matrix at row-index = item_x, and column-index = item_y.
        """
        max_limit, _ = self.board.shape
        if item_x == item_y and item_x + item_y == max_limit - 1:
            return self.left_diagonal_has_same_values(item, item_x, item_y) or \
            self.right_diagonal_has_same_values(item, item_x, item_y)

        if item_x == item_y:
            # elements on the left diagonal have same row and column value.
            return self.left_diagonal_has_same_values(item, item_x, item_y)

        if item_x + item_y == max_limit - 1:
            # elements on the right diagonal have sum of the row and column value as the same number.
            return self.right_diagonal_has_same_values(item, item_x, item_y)
        # Else, it is not either of the diagonals
        return False

    def is_game_over(self, player, item, item_x, item_y):
        """
        Check if the game is over, which is defined by a row, column or diagonal having
        the same values as the latest inserted integer `item`.

        params

        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        - item int: The latest integer inserted into the matrix at row-index = item_x, and column-index = item_y.
        """
        return self.cols_have_same_values(item, item_x, item_y) or \
                    self.rows_have_same_values(item, item_x, item_y) or \
                    self.element_diagonal_has_same_value(item, item_x, item_y)

    def is_winning_move(self, player, item, item_x, item_y):
        """
        Check if the last move was a winning move, which is defined by a row, column or diagonal having
        the same values as the latest inserted integer `item`.

        params

        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        - item int: The latest integer inserted into the matrix at row-index = item_x, and column-index = item_y.
        """
        if self.is_game_over(player, item, item_x, item_y):
            self.winner = player
            return True
        return False

    def is_stale(self):
        """
        Checks if there is no vacant space on the board
        """
        x, y = np.where(self.board == 0)
        if len(x) == 0 and len(y) == 0:
            self.stale = True
        log('is game stale? ', self.stale)
        return self.stale


    def player_move(self, input_symbol, item_x, item_y):
        """
        The method which facilitates insertion of values into the board matrix.

        params:

        - input_symbol: 'X' or 'O'
        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        """
        symbol = None

        if input_symbol == self.sym_o.get('mark'):
            # If 'O' was inserted
            symbol = self.sym_o

        elif input_symbol == self.sym_x.get('mark'):
            # If 'X' was inserted
            symbol = self.sym_x

        else:
            # invalid symbol
            return
        if self.board[item_x][item_y] == 0:
            self.board[item_x][item_y] = symbol.get('value')
            # insert the integer corresponding to the symbol in to the matrix.

            self.draw_board()
            # Show the board in a human friendly format for evaluation.

            if self.is_winning_move(symbol.get('mark'), symbol.get('value'), item_x, item_y):
                # If this move was a winning move, declare the symbol as the winner.
                print('Winner is: {}'.format(self.winner))
                return self.winner
            elif self.is_stale():
                print('Draw')
                return 'draw'

    def play(self, item_x, item_y):
        """
        The method exposed to a human user
        facilitates insertion of values into the board matrix.

        params:

        - input_symbol: 'X' or 'O'
        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        """
        max_limit, _ = self.board.shape
        if item_x > max_limit - 1 or item_y > max_limit:
            # If the row, column values dont' exist in the board matrix.
            # Exit without inserting it into the board.
            return
        self.player_move(self.player_sym.get('mark'), item_x, item_y)

    def bot_play(self, item_x, item_y):
        """
        The method exposed to a bot
        facilitates insertion of values into the board matrix.

        params:

        - input_symbol: 'X' or 'O'
        - item_x int: The row of the matrix in which item has been inserted.
        - item_y int: The column of the matrix in which the item has been inserted.
        """
        max_limit, _ = self.board.shape
        if item_x > max_limit - 1 or item_y > max_limit:
            return
        self.player_move(self.bot_sym.get('mark'), item_x, item_y)