backgammon/board.py

from cup import Cup
import numpy as np

class Board:

    # TODO: Remember to handle pushing other pieces to home
    # TODO: Also remember that a player can't move backwards and the one
    #  player goes from 1-47 while the other goes from 47-1

    def __init__(self):
        self.state = [ 0,
                       2, 0, 0, 0, 0, -5,
                       0, -3, 0, 0, 0, 5,
                       -5, 0, 0, 0, 3, 0,
                       5, 0, 0, 0, 0, -2,
                       0, 0, 0 ]
        

    def get_state(self):
        return self.state

    # Remember to handle edge case when we're on the last moves and you may go
    # from position 22 -> 24 on a 6, if you have no pieces behind 22. Simply
    # check if any are behind if you're circle or if any are higher if you are
    # X, then it can be allowed.

    # Also, the check_move will also fail when you're attempting to leave a
    # bar. A fix of this is of course to check if the from_idx = bar and if so,
    # allow some extra stuff!

    # TODO: write tests
    # FIXME: make sure to disallow backwards movement
    # TODO: implement double roll feature (4 dice if dice are equal)
    # TODO: implement moving checkers into home (bearing off)
    # TODO: handle barring in a more elengant way
    # TODO: allow bearing off with non-exact die roll if this is only possible
    #       move
    def check_move(self, move, player, roll):
        from_idx   = int(move[0])
        to_idx     = int(move[1])
        to_state   = self.state[to_idx]
        from_state = self.state[from_idx]
        
        if from_idx == 26:
            from_idx = 1
            roll -= 1
        elif from_idx == 27:
            from_idx = 24
            roll -= 1
            
        if not (1 <= from_idx <= 24 and
                1 <= to_idx <= 24):
            return False
        elif ( abs( from_idx - to_idx ) != roll ):
            return False
        elif (from_state *  player >= 1 and  # Is moving player's own checker?
              (to_state  *  player >= 0 or   # Is 'to' empty or has player's own checkers?
               to_state  * -player == 1)):   # Can opponent checker be hit?
            return True

    def find_pieces_for_player(self, player):
        idxs = []
        for idx, pip in enumerate(self.state):
            if pip * player >= 1:
                idxs.append(idx)
        return idxs

    def is_winner(self, player):
        for i in range(1,25):
            if player * self.state[i] > 0:
                return False
        return True
        
    
    def find_legal_moves(self, player, roll):
        # Find all pips with things on them belonging to the player
        # Iterate through each index and check if it's a possible move given the roll
        # If player is O, then check for idx + roll
        # If player is X, then check for idx - roll
        
        # Rewrite this, it's shit.
        idxs_with_thing = self.find_pieces_for_player(player)
        legal_moves = []

        for index in idxs_with_thing:
            from_idx = index
            to_idx = index+(roll*player)
            if self.check_move([from_idx,to_idx], player, roll):
                legal_moves.append([from_idx,to_idx])

        return legal_moves
    
    def pretty(self):
        temp = []
        for x in self.state:
            if x >= 0:
                temp.append(" {}".format(x))
            else:
                temp.append("{}".format(x))
                
        return """
  13  14  15  16  17  18               19  20  21  22  23  24
--------------------------------------------------------------------------
| {12}| {11}| {10}| {9}| {8}| {7}| bar  1: {26} | {6}| {5}| {4}| {3}| {2}| {1}| end -1: {0}|
|---|---|---|---|---|---|-----------|---|---|---|---|---|---|
| {13}| {14}| {15}| {16}| {17}| {18}| bar -1: {27} | {19}| {20}| {21}| {22}| {23}| {24}| end  1: {25}|
--------------------------------------------------------------------------
  12  11  10   9   8   7                6   5   4   3   2   1 
 """.format(*temp)
    def move_to_bar(self, to_idx):
        # Find the owner of the hit checker
        player = self.state[to_idx]

        # FIXME: find better bar solution
        if player == 1:
            self.state[26] += player
        else:
            self.state[27] += player

        self.state[to_idx] = 0

    def move_thing(self, player, from_idx, to_idx):
        self.state[from_idx] -= player
            
        if self.state[to_idx] * player == -1:
            self.move_to_bar(to_idx)
                
        self.state[to_idx] += player