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# connectfour.py

# From Classic Computer Science Problems in Python Chapter 8

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

# http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

from __future__ import annotations

from typing import List, Optional, Tuple

from enum import Enum

from board import Piece, Board, Move

class C4Piece(Piece, Enum):

B = "B"

R = "R"

E = " " # stand-in for empty

@property

def opposite(self) -> C4Piece:

if self == C4Piece.B:

return C4Piece.R

elif self == C4Piece.R:

return C4Piece.B

else:

return C4Piece.E

def __str__(self) -> str:

return self.value

def generate_segments(num_columns: int, num_rows: int, segment_length: int) -> List[List[Tuple[int, int]]]:

segments: List[List[Tuple[int, int]]] = []

# generate the vertical segments

for c in range(num_columns):

for r in range(num_rows - segment_length + 1):

segment: List[Tuple[int, int]] = []

for t in range(segment_length):

segment.append((c, r + t))

segments.append(segment)

# generate the horizontal segments

for c in range(num_columns - segment_length + 1):

for r in range(num_rows):

segment = []

for t in range(segment_length):

segment.append((c + t, r))

segments.append(segment)

# generate the bottom left to top right diagonal segments

for c in range(num_columns - segment_length + 1):

for r in range(num_rows - segment_length + 1):

segment = []

for t in range(segment_length):

segment.append((c + t, r + t))

segments.append(segment)

# generate the top left to bottom right diagonal segments

for c in range(num_columns - segment_length + 1):

for r in range(segment_length - 1, num_rows):

segment = []

for t in range(segment_length):

segment.append((c + t, r - t))

segments.append(segment)

return segments

class C4Board(Board):

NUM_ROWS: int = 6

NUM_COLUMNS: int = 7

SEGMENT_LENGTH: int = 4

SEGMENTS: List[List[Tuple[int, int]]] = generate_segments(NUM_COLUMNS, NUM_ROWS, SEGMENT_LENGTH)

class Column:

def __init__(self) -> None:

self._container: List[C4Piece] = []

@property

def full(self) -> bool:

return len(self._container) == C4Board.NUM_ROWS

def push(self, item: C4Piece) -> None:

if self.full:

raise OverflowError("Trying to push piece to full column")

self._container.append(item)

def __getitem__(self, index: int) -> C4Piece:

if index > len(self._container) - 1:

return C4Piece.E

return self._container[index]

def __repr__(self) -> str:

return repr(self._container)

def copy(self) -> C4Board.Column:

temp: C4Board.Column = C4Board.Column()

temp._container = self._container.copy()

return temp

def __init__(self, position: Optional[List[C4Board.Column]] = None, turn: C4Piece = C4Piece.B) -> None:

if position is None:

self.position: List[C4Board.Column] = [C4Board.Column() for _ in range(C4Board.NUM_COLUMNS)]

else:

self.position = position

self._turn: C4Piece = turn

@property

def turn(self) -> Piece:

return self._turn

def move(self, location: Move) -> Board:

temp_position: List[C4Board.Column] = self.position.copy()

for c in range(C4Board.NUM_COLUMNS):

temp_position[c] = self.position[c].copy()

temp_position[location].push(self._turn)

return C4Board(temp_position, self._turn.opposite)

@property

def legal_moves(self) -> List[Move]:

return [Move(c) for c in range(C4Board.NUM_COLUMNS) if not self.position[c].full]

# Returns the count of black & red pieces in a segment

def _count_segment(self, segment: List[Tuple[int, int]]) -> Tuple[int, int]:

black_count: int = 0

red_count: int = 0

for column, row in segment:

if self.position[column][row] == C4Piece.B:

black_count += 1

elif self.position[column][row] == C4Piece.R:

red_count += 1

return black_count, red_count

@property

def is_win(self) -> bool:

for segment in C4Board.SEGMENTS:

black_count, red_count = self._count_segment(segment)

if black_count == 4 or red_count == 4:

return True

return False

def _evaluate_segment(self, segment: List[Tuple[int, int]], player: Piece) -> float:

black_count, red_count = self._count_segment(segment)

if red_count > 0 and black_count > 0:

return 0 # mixed segments are neutral

count: int = max(red_count, black_count)

score: float = 0

if count == 2:

score = 1

elif count == 3:

score = 100

elif count == 4:

score = 1000000

color: C4Piece = C4Piece.B

if red_count > black_count:

color = C4Piece.R

if color != player:

return -score

return score

def evaluate(self, player: Piece) -> float:

total: float = 0

for segment in C4Board.SEGMENTS:

total += self._evaluate_segment(segment, player)

return total

def __repr__(self) -> str:

display: str = ""

for r in reversed(range(C4Board.NUM_ROWS)):

display += "|"

for c in range(C4Board.NUM_COLUMNS):

display += f"{self.position[c][r]}" + "|"

display += "\n"

return display