the FEN notation can be read to create a position

selected piece

.github/workflows/automatic-prerelease.yml

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+---
+name: "pre-release"
+
+on:
+  push:
+    branches:
+      - "main"
+
+jobs:
+  pre-release:
+    name: "Pre Release"
+    runs-on: "ubuntu-latest"
+
+    steps:
+      - uses: "marvinpinto/action-automatic-releases@latest"
+        with:
+          repo_token: "${{ secrets.GITHUB_TOKEN }}"
+          prerelease: true
+          automatic_release_tag: "latest"
+          title: "Development Build"

.github/workflows/tagged-release.yml

@@ -0,0 +1,18 @@
+---
+name: "tagged-release"
+
+on:
+  push:
+    tags:
+      - "v*"
+
+jobs:
+  tagged-release:
+    name: "Tagged Release"
+    runs-on: "ubuntu-latest"
+
+    steps:
+      - uses: "marvinpinto/action-automatic-releases@latest"
+        with:
+          repo_token: "${{ secrets.GITHUB_TOKEN }}"
+          prerelease: false

src/logic/board.py

@@ -0,0 +1,114 @@
+from logic.pieces.bishop import Bishop
+from logic.pieces.king import King
+from logic.pieces.knight import Knight
+from logic.pieces.queen import Queen
+from logic.pieces.rook import Rook
+from logic.pieces.pawn import Pawn
+from logic.pieces.piece import Piece
+from logic.position import Position
+
+from typing import Type
+
+class Board:
+    KING_SIDE_CASTLE = "king side castle"
+    QUEEN_SIDE_CASTLE = "queen side castle"
+    def __init__(self) -> None:
+        self._white: dict[Position, Piece] = {}
+        self._black: dict[Position, Piece] = {}
+        self._turn = None
+        self._white_castling_write = set()
+        self._black_castling_write = set()
+        self._en_passant_target = None
+
+    @staticmethod
+    def _piece_class_from_char(c: str) -> Type[Piece]:
+        assert len(c) == 1, f"The piece {c} isn't denoted by 1 character"
+        c = c.lower()
+        if c == "p":
+            return Pawn
+        if c == "r":
+            return Rook
+        if c == "n":
+            return Knight
+        if c == "b":
+            return Bishop
+        if c == "q":
+            return Queen
+        if c == "k":
+            return King
+        raise ValueError(f"Unknown piece '{c}'")
+
+    @staticmethod
+    def setup_FEN_position(position: str) -> "Board":
+        ret = Board()
+
+        # -- Pieces
+        pieces = "prnbqk" # possible pieces
+        numbers = "12345678" # possible number of empty squares
+
+        x = 0
+        y = 7 # FEN starts from the top left, so 8th rank
+        for c in position:
+            if c == " ":
+                break
+            if c in pieces or c in pieces.upper():
+                pos = Position(x, y)
+                piece = Board._piece_class_from_char(c)
+                if c.isupper():
+                    ret._white[pos] = piece(pos, Piece.WHITE)
+                else:
+                    ret._black[pos] = piece(pos, Piece.BLACK)
+
+                x += 1
+                continue
+            if c in numbers:
+                x += int(c)
+            if c == '/':
+                x = 0
+                y -= 1
+
+
+        # -- Active colour
+        index = position.find(" ") # find the first space
+        index += 1
+        if position[index] == "w":
+            ret._turn = Piece.WHITE
+        elif position[index] == "b":
+            ret._turn = Piece.BLACK
+        else:
+            raise ValueError(f"The FEN position is malformed, the active colour should be either 'w' or 'b', but is '{position[index]}'")
+
+
+        # -- Castling Rights
+        for c in position:
+            if c == "-" or c == " ":
+                break
+
+            sides = "kq"
+            assert c in sides or c in sides.upper(), f"The FEN position is malformed, the castling rights should be either k or q (both either lower- or upper-case), instead is '{c}'"
+            if c == "K":
+                ret._white_castling_write.add(Board.KING_SIDE_CASTLE)
+            if c == "Q":
+                ret._white_castling_write.add(Board.QUEEN_SIDE_CASTLE)
+            if c == "k":
+                ret._black_castling_write.add(Board.KING_SIDE_CASTLE)
+            if c == "q":
+                ret._black_castling_write.add(Board.QUEEN_SIDE_CASTLE)
+
+        # -- En passant target
+        index = position.find(" ", index + 1)
+        if position[index] != "-":
+            ret._en_passant_target = position[index:index+2]
+
+        return ret
+
+    def piece_at(self, x: int, y: int) -> Piece | None:
+        pos = Position(x, y)
+        white_piece = self._white.get(pos, None)
+        black_piece = self._black.get(pos, None)
+
+        assert white_piece == None or black_piece == None, f"There are two pieces at the same position {pos}, this shouldn't happen!"
+
+        if white_piece != None:
+            return white_piece
+        return black_piece

src/logic/pieces/bishop.py

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+from .piece import Piece
+
+class Bishop(Piece):
+    pass

src/logic/pieces/king.py

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+from .piece import Piece
+
+class King(Piece):
+    pass
+

src/logic/pieces/knight.py

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+from .piece import Piece
+
+class Knight(Piece):
+    pass
+

src/logic/pieces/pawn.py

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+from logic.position import Position
+from logic.pieces.piece import Piece
+
+class Pawn(Piece):
+    def legal_moves(self, board) -> list[Position]:
+        ret = []
+
+        # can we capture to the left?
+        if self.pos.x > 0 and (
+            (self.colour == self.WHITE and (capturable_piece := board.piece_at(self.pos.x - 1, self.pos.y + 1)))
+            or
+            (self.colour == self.BLACK and (capturable_piece := board.piece_at(self.pos.x - 1, self.pos.y - 1)))
+        ):
+            if capturable_piece.colour != self.colour:
+                ret.append(capturable_piece.pos)
+
+        # can we capture to the right?
+        if self.pos.x < 7 and (
+            (self.colour == self.WHITE and (capturable_piece := board.piece_at(self.pos.x + 1, self.pos.y + 1)))
+            or
+            (self.colour == self.BLACK and (capturable_piece := board.piece_at(self.pos.x + 1, self.pos.y - 1)))
+        ):
+            if capturable_piece.colour != self.colour:
+                ret.append(capturable_piece.pos)
+
+        for dy in range(1, 3 if self.pos.y == 1 else 2):
+            if self.pos.y + dy > 7 or board.piece_at(self.pos.x, self.pos.y + dy):
+                break
+            ret.append(Position(self.pos.x, self.pos.y + dy))
+
+        return ret

src/logic/pieces/piece.py

@@ -0,0 +1,17 @@
+from logic.position import Position
+
+
+class Piece:
+    WHITE = "white"
+    BLACK = "black"
+
+    def __init__(self, pos, colour) -> None:
+        self.pos = pos
+        assert colour == self.WHITE or colour == self.BLACK, "The colour of the piece must be either Piece.WHITE or Piece.BLACK"
+        self.colour = colour
+
+    def position(self) -> Position:
+        return self.pos
+
+    def legal_moves(self, board) -> list[Position]:
+        raise NotImplementedError(f"Can't say what the legal moves are for {type(self).__name__}, the method hasn't been implemented yet")

src/logic/pieces/queen.py

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+from .piece import Piece
+
+class Queen(Piece):
+    pass
+

src/logic/pieces/rook.py

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+from .piece import Piece
+
+class Rook(Piece):
+    pass
+

src/logic/position.py

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+class Position:
+    _MIN_POS = 0
+    _MAX_POS = 7
+
+    def __init__(self, x, y) -> None:
+        assert x >= self._MIN_POS and x <= self._MAX_POS, f"Invalid argument: x should be between {self._MIN_POS} and {self._MAX_POS}, but is {x}"
+        assert y >= self._MIN_POS and y <= self._MAX_POS, f"Invalid argument: y should be between {self._MIN_POS} and {self._MAX_POS}, but is {y}"
+
+        self.x = x
+        self.y = y
+
+    def __eq__(self, value: object, /) -> bool:
+        if type(value) != type(self):
+            return False
+        return value.x == self.x and value.y == self.y
+
+    def __hash__(self) -> int:
+        return hash((self.x, self.y))
+
+    def __str__(self) -> str:
+        return f"{self.x, self.y}"
+
+    def __repr__(self) -> str:
+        return str(self)
+

src/main.py

@@ -0,0 +1,11 @@
+from logic.board import Board, create_board
+from view.gui import GUI
+from view.tui import TUI
+
+if __name__ == "__main__":
+    initial_board_position = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w"
+    board = Board.setup_FEN_position(initial_board_position)
+
+    view = GUI(board)
+
+    view.show()

src/view/gui.py

@@ -0,0 +1,94 @@
+import tkinter as tk
+
+from logic.board import Board
+from logic.pieces.piece import Piece
+from logic.position import Position
+from view.view import View
+
+class GUI(View):
+    def __init__(self, board: Board) -> None:
+        super().__init__(board)
+
+        self.root = tk.Tk()
+        self.root.title("Chess Board")
+
+        self.tile_size = 80
+        board_size = self.tile_size * 8
+
+        self.canvas = tk.Canvas(self.root, width=board_size, height=board_size)
+        self.canvas.pack()
+
+        self.state = {"selected_piece": None, "legal_moves": []}
+
+        self.canvas.bind("<Button-1>", self._on_canvas_click)
+        self._draw_chess_board()
+
+
+    def _draw_chess_board(self):
+        colours = ["#F0D9B5", "#B58863"]  # Light and dark squares
+
+        for y in range(8):
+            for x in range(8):
+                colour = colours[(x + y) % 2]
+                if self.state["selected_piece"] and Position(x, 7-y) in self.state["legal_moves"]:
+                    colour = "#ADD8E6"  # Highlight legal moves
+
+                self.canvas.create_rectangle(
+                    x * self.tile_size, 
+                    y * self.tile_size, 
+                    (x + 1) * self.tile_size, 
+                    (y + 1) * self.tile_size, 
+                    fill=colour
+                )
+
+                piece = self.board.piece_at(x, 7-y)
+
+                if piece:
+                    text_colour = "white" if piece.colour == Piece.WHITE else "black"
+                    self.canvas.create_text(
+                        (x + 0.5) * self.tile_size, 
+                        (y + 0.5) * self.tile_size, 
+                        text=piece.__class__.__name__[0], 
+                        fill=text_colour, 
+                        font=("Arial", 32, "bold")
+                    )
+
+                # Cell annotations
+                text_colour = colours[(x + y + 1) % 2] # the other colour
+
+                if x == 0: # numbers in the top left of the first column
+                    self.canvas.create_text(
+                        (x + 0.15) * self.tile_size, 
+                        (y + 0.15) * self.tile_size, 
+                        text=8-y, 
+                        fill=text_colour, 
+                        font=("Arial", 10, "bold")
+                    )
+                if y == 7: # numbers in the top left of the first column
+                    self.canvas.create_text(
+                        (x + 0.85) * self.tile_size, 
+                        (y + 0.85) * self.tile_size, 
+                        text="abcdefgh"[x], 
+                        fill=text_colour, 
+                        font=("Arial", 10, "bold")
+                    )
+                    
+
+    def _on_canvas_click(self, event):
+        x, y = event.x // self.tile_size, event.y // self.tile_size
+        y = 7 - y
+        piece = self.board.piece_at(x, y)
+        print(f"Clicked on {x, y}, {piece = }")
+
+        if piece:
+            self.state["selected_piece"] = piece
+            self.state["legal_moves"] = piece.legal_moves(self.board)
+        else:
+            self.state["selected_piece"] = None
+            self.state["legal_moves"] = []
+
+        self.canvas.delete("all")
+        self._draw_chess_board()
+
+    def show(self) -> None:
+        self.root.mainloop()

src/view/tui.py

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+from logic.board import Board
+from logic.pieces.bishop import Bishop
+from logic.pieces.king import King
+from logic.pieces.knight import Knight
+from logic.pieces.pawn import Pawn
+from logic.pieces.piece import Piece
+from logic.pieces.queen import Queen
+from logic.pieces.rook import Rook
+from view.view import View
+
+class TUI(View):
+    def __init__(self, board: Board) -> None:
+        super().__init__(board)
+
+    def show(self) -> None:
+        board_view = [
+            [" " for _ in range(0, 8)]
+            for _ in range(0, 8)
+        ]
+
+        for pos, piece in self.board._white.items():
+            board_view[pos.y][pos.x] = self.string_of(piece).upper()
+
+        for pos, piece in self.board._black.items():
+            board_view[pos.y][pos.x] = self.string_of(piece)
+
+        # we reverse the board because (0, 0) in in the bottom left, not top left
+        board_view.reverse()
+        print(self.to_string(board_view))
+
+    def to_string(self, board_view: list[list[str]]) -> str:
+        VER_SEP = "|"
+        HOR_SEP = "-"
+        ROW_SEP = HOR_SEP * (2*len(board_view[0]) + 1)
+        ret = ROW_SEP + "\n"
+        for row_view in board_view:
+            row_str = VER_SEP + VER_SEP.join(row_view) + VER_SEP
+            ret += row_str + "\n"
+            ret += ROW_SEP + "\n"
+
+        return ret
+
+    def string_of(self, piece: Piece) -> str:
+        type_ = type(piece) 
+        if type_ == Pawn:
+            return "p"
+        if type_ == Queen:
+            return "q"
+        if type_ == Bishop:
+            return "b"
+        if type_ == Knight:
+            return "n"
+        if type_ == Rook:
+            return "r"
+        if type_ == King:
+            return "k"
+        raise ValueError(f"Unknown piece type {type(piece)}")

src/view/view.py

@@ -0,0 +1,10 @@
+from logic.board import Board
+
+
+class View:
+    def __init__(self, board: Board) -> None:
+        self.board: Board = board
+
+    def show(self) -> None:
+        raise NotImplementedError(f"Can't show the board, the show() method of {type(self)} is not implemented")
+