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import tables
from strutils import parseInt
type
Color* = enum
Black = -1, White = 1
## Board that saves the pieces
Pieces* = array[0..119, int]
## Board that checks if pieces moved
Moved* = array[0..119, bool]
## Game as object of different values
Game* = object
pieces*: Pieces
moved: Moved
to_move*: Color
## Move as object
Move* = object
start: int
dest: int
color: Color
prom: int
const
# IDs for piece
BlockID* = 999
PawnID* = 1
KnightID* = 2
BishopID* = 3
RookID* = 4
QueenID* = 5
KingID* = 6
EnPassantID* = 7
# IDs that are saved in the array
Block* = BlockID
WPawn* = PawnID
WKnight* = KnightID
WBishop* = BishopID
WRook* = RookID
WQueen* = QueenID
WKing* = KingID
WEnPassant* = EnPassantID
BPawn* = -PawnID
BKnight* = -KnightID
BBishop* = -BishopID
BRook* = -RookID
BQueen* = -QueenID
BKing* = -KingID
BEnPassant* = EnPassantID
# Directions of movement
N = 10
S = -N
W = 1
E = -W
# Movement options for pieces (Bishop/Rook/Queen can repeat in the same direction)
Knight_Moves = [N+N+E, N+N+W, E+E+N, E+E+S, S+S+E, S+S+W, W+W+N, W+W+S]
Bishop_Moves = [N+E, N+W, S+E, S+W]
Rook_Moves = [N, E, S, W]
Queen_Moves = [N, E, S, W, N+E, N+W, S+E, S+W]
King_Moves = [N, E, S, W, N+E, N+W, S+E, S+W]
King_Moves_White_Castle = [E+E, W+W]
Pawn_Moves_White = [N]
Pawn_Moves_White_Double = [N+N]
Pawn_Moves_White_Attack = [N+E, N+W]
var PieceChar = {
0: " ",
1: "P",
2: "N",
3: "B",
4: "R",
5: "Q",
6: "K",
7: " ",
-1: "p",
-2: "n",
-3: "b",
-4: "r",
-5: "q",
-6: "k",
-7: " ",
999: "-"
}.newTable
var FileChar = {
"a": 7,
"b": 6,
"c": 5,
"d": 4,
"e": 3,
"f": 2,
"g": 1,
"h": 0
}.newTable
proc init_board(): Pieces =
## Create and return a board with pieces in starting position.
let board = [
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, WRook, WKnight, WBishop, WKing, WQueen, WBishop, WKnight, WRook, Block,
Block, WPawn, WPawn, WPawn, WPawn, WPawn, WPawn, WPawn, WPawn, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, 0, 0, 0, 0, 0, 0, 0, 0, Block,
Block, BPawn, BPawn, BPawn, BPawn, BPawn, BPawn, BPawn, BPawn, Block,
Block, BRook, BKnight, BBishop, BKing, BQueen, BBishop, BKnight, BRook, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block,
Block, Block, Block, Block, Block, Block, Block, Block, Block, Block]
return board
proc get_move*(start: int, dest: int, prom: int, color: Color): Move =
## Get a move object from `start` to `dest` with an eventual promition to `prom`
var move = Move(start: start, dest: dest, prom: prom * ord(color), color: color)
if (KnightID > prom or QueenID < prom):
move.prom = QueenID
return move
proc get_move*(start: int, dest: int, color: Color): Move =
## Get a move object from `start` to `dest` with automatic promition to `queen`
var move = Move(start: start, dest: dest, prom: QueenID * ord(color), color: color)
return move
proc init_moved(): Moved =
## Create and return a board of pieces moved.
var moved: Moved
return moved
proc init_game*(): Game =
## Create and return a Game object.
let game = Game(pieces: init_board(), moved: init_moved(),
to_move: Color.White)
return game
proc get_field(pieces: Pieces, field: int): int =
return pieces[field]
proc set_field(pieces: var Pieces, field: int, val: int): bool {.discardable.} =
if (val in PieceChar):
try:
pieces[field] = val
return true
except Exception:
return false
proc get_field(moved: Moved, field: int): bool =
return moved[field]
proc set_field(moved: var Moved, field: int, val: bool): bool {.discardable.} =
try:
moved[field] = val
return true
except Exception:
return false
proc echo_board*(game: Game, color: Color) =
## Prints out the given `board` with its pieces as characters and line indices from perspecive of `color`.
var line_str = ""
if (color == Color.Black):
for i in countup(0, len(game.pieces)-1):
if (game.pieces.get_field(i) == 999):
continue
line_str &= PieceChar[game.pieces[i]] & " "
if ((i+2) %% 10 == 0):
line_str &= $((int)((i)/10)-1) & "\n"
echo line_str
echo "h g f e d c b a"
else:
for i in countdown(len(game.pieces)-1, 0):
if (game.pieces.get_field(i) == 999):
continue
line_str &= PieceChar[game.pieces[i]] & " "
if ((i-1) %% 10 == 0):
line_str &= $((int)((i)/10)-1) & "\n"
echo line_str
echo "a b c d e f g h"
proc field_to_ind*(file: string, line: int): int =
## Calculate board index from `file` and `line` of a chess board.
try:
return 1+(line+1)*10+FileChar[file]
except IndexDefect, ValueError:
return -1
proc field_to_ind*(field: string): int =
## Calculate board index from `field` of a chess board.
try:
return field_to_ind($field[0], parseInt($field[1]))
except IndexDefect, ValueError:
return -1
proc ind_to_field*(ind: int): string =
## Calculate field name from board index `ind`.
let line = (int)ind/10-1
let file_ind = (ind)%%10-1
for file, i in FileChar:
if FileChar[file] == file_ind:
return $file & $line
proc gen_bishop_dests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a bishop with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in Bishop_Moves:
dest = field+move
target = game.pieces.get_field(dest)
while (target != 999 and (ord(color) * target <= 0) or target == EnPassantID):
res.add(dest)
if (ord(color) * target < 0 and ord(color) * target > -EnPassantID):
break
dest = dest+move
target = game.pieces.get_field(dest)
return res
except IndexDefect:
return @[]
proc gen_rook_dests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a rook with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in Rook_Moves:
dest = field+move
target = game.pieces.get_field(dest)
while (target != 999 and (ord(color) * target <= 0) or target == EnPassantID):
res.add(dest)
if (ord(color) * target < 0 and ord(color) * target > -EnPassantID):
break
dest = dest+move
target = game.pieces.get_field(dest)
return res
except IndexDefect:
return @[]
proc gen_queen_dests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a queen with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in Queen_Moves:
dest = field+move
target = game.pieces.get_field(dest)
while (target != 999 and (ord(color) * target <= 0) or target == EnPassantID):
res.add(dest)
if (ord(color) * target < 0 and ord(color) * target > -EnPassantID):
break
dest = dest+move
target = game.pieces.get_field(dest)
return res
except IndexDefect:
return @[]
proc gen_king_castle_dest(game: Game, field: int, color: Color): seq[int] =
## Generate possible castle destinations for a king with specific `color` located at index `field` of `game`
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
var half_dest: int
var half_target: int
for castle in King_Moves_White_Castle:
dest = field + castle
target = game.pieces.get_field(dest)
half_dest = field + (int) castle/2
half_target = game.pieces.get_field(half_dest)
if (target == 999 or (target != 0)):
continue
if (half_target == 999 or (half_target != 0)):
continue
res.add(dest)
return res
except IndexDefect:
return @[]
proc gen_king_dests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a king with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in King_Moves:
dest = field + move
target = game.pieces.get_field(dest)
if (target == 999 or (ord(color) * target > 0 and ord(color) * target != EnPassantID)):
continue
res.add(dest)
res.add(game.gen_king_castle_dest(field, color))
return res
except IndexDefect:
return @[]
proc gen_knight_dests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a knight with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in Knight_Moves:
dest = field + move
target = game.pieces.get_field(dest)
if (target == 999 or (ord(color) * target > 0 and ord(color) * target != EnPassantID)):
continue
res.add(dest)
return res
except IndexDefect:
return @[]
proc gen_pawn_attack_dests(game: Game, field: int, color: Color): seq[int] =
## Generate possible attack destinations for a pawn with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for attacks in Pawn_Moves_White_Attack:
dest = field + attacks * ord(color)
target = game.pieces.get_field(dest)
if (target == 999 or ord(color) * target >= 0):
continue
res.add(dest)
return res
except IndexDefect:
return @[]
proc gen_pawn_double_dests(game: Game, field: int, color: Color): seq[int] =
## Generate possible double destinations for a pawn with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for doubles in Pawn_Moves_White_Double:
dest = field + doubles * ord(color)
target = game.pieces.get_field(dest)
if (game.moved.get_field(field) or (target != 0) or (game.pieces.get_field(dest+(S*ord(color))) != 0)):
continue
res.add(dest)
return res
except IndexDefect:
return @[]
proc gen_pawn_dests(game: Game, field: int, color: Color): seq[int] =
## Generate possible destinations for a pawn with specific `color` located at index `field` of `game`.
## Returns a sequence of possible indices to move to.
try:
var res = newSeq[int]()
var dest: int
var target: int
for move in Pawn_Moves_White:
dest = field + move * ord(color)
target = game.pieces.get_field(dest)
if (target != 0 and target != ord(color) * EnPassantID):
continue
res.add(dest)
res.add(game.gen_pawn_attack_dests(field, color))
res.add(game.gen_pawn_double_dests(field, color))
return res
except IndexDefect:
return @[]
proc piece_on(game: Game, color: Color, sequence: seq[int],
pieceID: int): bool =
## Check if a piece with `pieceID` of a given `color` is in a field described in a `sequence` in a `game`.
for check in sequence:
if game.pieces.get_field(check) == ord(color) * -1 * pieceID:
return true
return false
proc is_attacked(game: Game, position: int, color: Color): bool =
## Check if a field is attacked by the opposite of `color` in a `game`.
var attacked = false
attacked = attacked or game.piece_on(color, game.gen_pawn_attack_dests(position,
color), PawnID)
attacked = attacked or game.piece_on(color, game.gen_queen_dests(position,
color), QueenID)
attacked = attacked or game.piece_on(color, game.gen_king_dests(position,
color), KingID)
attacked = attacked or game.piece_on(color, game.gen_rook_dests(position,
color), RookID)
attacked = attacked or game.piece_on(color, game.gen_bishop_dests(position,
color), BishopID)
attacked = attacked or game.piece_on(color, game.gen_knight_dests(position,
color), KnightID)
return attacked
proc is_in_check*(game: Game, color: Color): bool =
## Check if the King of a given `color` is in check in a `game`.
var king_pos: int
for i in countup(0, game.pieces.high):
if game.pieces.get_field(i) == ord(color) * KingID:
king_pos = i
return game.is_attacked(king_pos, color)
proc unchecked_move(game: var Game, start: int, dest: int): bool {.discardable.} =
## Moves a piece if possible from `start` position to `dest` position.
## Doesnt check boundaries, checks, movement.
## returns true if the piece moved, else false
try:
let piece = game.pieces.get_field(start)
if game.pieces.set_field(start, 0):
if game.pieces.set_field(dest, piece):
game.moved.set_field(start, true)
game.moved.set_field(dest, true)
return true
else:
game.pieces.set_field(start, piece)
except IndexDefect, ValueError:
return false
proc move_leads_to_check(game: Game, start: int, dest: int,
color: Color): bool =
## Checks in a `game` if a move from `start` to `dest` puts the `color` king in check.
var check = game
check.unchecked_move(start, dest)
return check.is_in_check(color)
proc remove_en_passant(pieces: var Pieces, color: Color): void =
## Removes every en passant of given `color` from the `game`.
for field in pieces.low..pieces.high:
if pieces.get_field(field) == ord(color) * EnPassantID:
pieces.set_field(field,0)
proc gen_legal_knight_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal knight moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != KnightID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_knight_dests(field, color)
for dest in moves:
if not game.move_leads_to_check(field, dest, color):
res.add(get_move(field, dest, color))
return res
proc gen_legal_bishop_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal bishop moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != BishopID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_bishop_dests(field, color)
for dest in moves:
if not game.move_leads_to_check(field, dest, color):
res.add(get_move(field, dest, color))
return res
proc gen_legal_rook_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal rook moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != RookID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_rook_dests(field, color)
for dest in moves:
if not game.move_leads_to_check(field, dest, color):
res.add(get_move(field, dest, color))
return res
proc gen_legal_queen_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal queen moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != QueenID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_queen_dests(field, color)
for dest in moves:
if not game.move_leads_to_check(field, dest, color):
res.add(get_move(field, dest, color))
return res
proc gen_legal_king_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal king moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != KingID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_king_dests(field, color)
for dest in moves:
if field - dest == W+W and game.is_attacked(dest+W, color):
continue
if field - dest == E+E and game.is_attacked(dest+E, color):
continue
if not game.move_leads_to_check(field, dest, color):
res.add(get_move(field, dest, color))
return res
proc gen_pawn_promotion(move: Move, color: Color): seq[Move] =
## Generate all possible promotions of a `move` by `color`.
var promotions = newSeq[Move]()
let start = move.start
let dest = move.dest
if (90 < dest and dest < 99) or (20 < dest and dest < 29):
for piece in KnightID..QueenID:
promotions.add(get_move(start, dest, piece, color))
return promotions
proc gen_legal_pawn_moves(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal pawn moves starting from `field` in a `game` for a `color`.
if game.pieces.get_field(field) != PawnID * ord(color):
return @[]
var res = newSeq[Move]()
var moves = game.gen_pawn_dests(field, color)
for dest in moves:
if not game.move_leads_to_check(field, dest, color):
var promotions = gen_pawn_promotion(get_move(field, dest, color), color)
if promotions != @[]:
res.add(promotions)
else:
res.add(get_move(field, dest, color))
return res
proc gen_legal_moves*(game: Game, field: int, color: Color): seq[Move] =
## Generates all legal moves starting from `field` in a `game` for a `color`.
var legal_moves = newSeq[Move]()
var target = ord(color) * game.pieces.get_field(field)
if 0 < target and target < EnPassantID:
legal_moves = case target:
of PawnID:
game.gen_legal_pawn_moves(field, color)
of KnightID:
game.gen_legal_knight_moves(field, color)
of BishopID:
game.gen_legal_bishop_moves(field, color)
of RookID:
game.gen_legal_rook_moves(field, color)
of QueenID:
game.gen_legal_queen_moves(field, color)
of KingID:
game.gen_legal_king_moves(field, color)
else:
@[]
return legal_moves
proc gen_legal_moves*(game: Game, color: Color): seq[Move] =
## Generates all legal moves in a `game` for a `color`.
var legal_moves = newSeq[Move]()
for field in game.pieces.low..game.pieces.high:
legal_moves.add(game.gen_legal_moves(field, color))
return legal_moves
proc castling(game: var Game, kstart: int, dest_kingside: bool,
color: Color): bool {.discardable.} =
## Tries to castle in a given `game` with the king of a given `color` from `start`.
## `dest_kingside` for kingside castling, else castling is queenside.
## This process checks for the legality of the move and performs the switch of `game.to_move`
try:
if game.to_move != color:
return false
var kdest = kstart
var rstart: int
var rdest: int
if (dest_kingside):
kdest = kstart + (E+E)
rstart = kstart + (E+E+E)
rdest = rstart + (W+W)
else:
rstart = kstart + (W+W+W+W)
rdest = rstart + (E+E+E)
kdest = kstart + (W+W)
if not game.moved.get_field(kstart) and not game.moved.get_field(rstart):
var check = false
if (dest_kingside):
check = check or game.is_attacked(kstart, color)
check = check or game.is_attacked(kstart+(E), color)
check = check or game.is_attacked(kstart+(E+E), color)
else:
check = check or game.is_attacked(kstart, color)
check = check or game.is_attacked(kstart+(W), color)
check = check or game.is_attacked(kstart+(W+W), color)
if check:
return false
game.unchecked_move(kstart, kdest)
game.unchecked_move(rstart, rdest)
return true
return false
except IndexDefect, ValueError:
return false
proc checked_move*(game: var Game, move: Move): bool {.discardable.} =
## Tries to make a move in a given `game` with the piece of a given `color` from `start` to `dest`.
## This process checks for the legality of the move and performs the switch of `game.to_move`
try:
let start = move.start
let dest = move.dest
let color = move.color
let prom = move.prom
if game.to_move != color:
return false
var sequence = newSeq[Move]()
let piece = game.pieces.get_field(start)
var create_en_passant = false
var captured_en_passant = false
var move: Move
move = get_move(start, dest, color)
if (piece == PawnID * ord(color)):
create_en_passant = dest in game.gen_pawn_double_dests(start,color)
captured_en_passant = (game.pieces.get_field(dest) == -1 * ord(color) * EnPassantID)
sequence.add(game.gen_legal_moves(start, color))
if (move in sequence):
game.pieces.remove_en_passant(color)
if (piece == KingID * ord(color) and (start - dest == (W+W))):
game.castling(start, true, color)
elif (piece == KingID * ord(color) and (start - dest == (E+E))):
game.castling(start, false, color)
else:
game.unchecked_move(start, dest)
game.to_move = Color(ord(game.to_move)*(-1))
if create_en_passant:
game.pieces.set_field(dest-(N*ord(color)),EnPassantID * ord(color))
if captured_en_passant:
game.pieces.set_field(dest-(N*ord(color)),0)
if ((90 < dest and dest < 99) or (20 < dest and dest < 29)) and game.pieces.get_field(dest) == PawnID * ord(color):
game.pieces.set_field(dest, prom)
return true
except IndexDefect, ValueError:
return false
proc has_no_moves(game: Game, color: Color): bool =
## Checks if a player of a given `color` has no legal moves in a `game`.
return (game.gen_legal_moves(color) == @[])
proc is_checkmate*(game: Game, color: Color): bool =
## Checks if a player of a given `color` in a `game` is checkmate.
return game.has_no_moves(color) and game.is_in_check(color)
proc is_stalemate*(game: Game, color: Color): bool =
## Checks if a player of a given `color` in a `game` is stalemate.
return game.has_no_moves(color) and not game.is_in_check(color)