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#import "board.typ": at, copy-grid, find-pieces, is-black, is-white, on-board, piece-type |
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2
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#import "moves.typ": bishop-dirs, generate-moves-for, king-dirs, knight-offsets, pawn-moves, rook-dirs |
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3
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4
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#let is-attacked(grid, col, row, by-color) = { |
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let enemy(piece) = if by-color == "white" { is-white(piece) } else { is-black(piece) } |
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7
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// knight attacks |
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8
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for (dc, dr) in knight-offsets { |
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9
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let p = at(grid, col + dc, row + dr) |
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10
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if p != "." and piece-type(p) == "N" and enemy(p) { return true } |
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} |
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13
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// king attacks |
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14
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for (dc, dr) in king-dirs { |
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15
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let p = at(grid, col + dc, row + dr) |
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if p != "." and piece-type(p) == "K" and enemy(p) { return true } |
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} |
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19
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// pawn attacks |
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20
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let pawn-checks = if by-color == "white" { ((-1, 1), (1, 1)) } else { ((-1, -1), (1, -1)) } |
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21
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for (dc, dr) in pawn-checks { |
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let p = at(grid, col + dc, row + dr) |
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if p != "." and piece-type(p) == "P" and enemy(p) { return true } |
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} |
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26
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// sliding pieces |
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27
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for (dirs, types) in ((bishop-dirs, ("B", "Q")), (rook-dirs, ("R", "Q"))) { |
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28
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for (dc, dr) in dirs { |
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29
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let nc = col + dc |
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30
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let nr = row + dr |
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31
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while on-board(nc, nr) { |
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32
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let p = at(grid, nc, nr) |
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33
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if p != "." { |
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34
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if enemy(p) and types.contains(piece-type(p)) { return true } |
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35
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break // blocked by any piece |
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} |
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37
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nc += dc |
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nr += dr |
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39
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} |
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40
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} |
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41
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} |
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43
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false |
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44
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} |
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45
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46
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#let is-in-check(grid, turn) = { |
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let king-char = if turn == "white" { "K" } else { "k" } |
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48
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let enemy = if turn == "white" { "black" } else { "white" } |
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49
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for r in range(8) { |
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50
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for c in range(8) { |
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51
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if grid.at(r).at(c) == king-char { |
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return is-attacked(grid, c + 1, r + 1, enemy) |
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} |
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54
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} |
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} |
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56
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false |
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57
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} |
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58
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59
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#let can-castle(grid, row, empty-cols, check-cols, enemy) = { |
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if is-attacked(grid, 5, row, enemy) { return false } |
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for c in empty-cols { if at(grid, c, row) != "." { return false } } |
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for c in check-cols { if is-attacked(grid, c, row, enemy) { return false } } |
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true |
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} |
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65
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66
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#let has-legal-move(grid, turn, ep: none, castles: "") = { |
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67
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for r in range(8) { |
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68
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for c in range(8) { |
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69
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let p = grid.at(r).at(c) |
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70
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if p == "." { continue } |
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if turn == "white" and not is-white(p) { continue } |
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if turn == "black" and not is-black(p) { continue } |
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let type = piece-type(p) |
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75
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76
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let col = c + 1 |
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77
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let row = r + 1 |
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let raw-moves = if type == "P" { pawn-moves(grid, col, row, turn, ep: ep) } else { |
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generate-moves-for(grid, col, row, turn, ep: ep) |
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} |
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81
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82
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for m in raw-moves { |
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let (dc, dr) = (m.at(0), m.at(1)) |
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84
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let new-grid = copy-grid(grid) |
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85
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new-grid.at(r).at(c) = "." |
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86
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let mover = p |
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87
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let is-pawn = type == "P" |
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if is-pawn and (dr == 1 or dr == 8) { |
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mover = if turn == "white" { "Q" } else { "q" } |
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90
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} |
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91
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new-grid.at(dr - 1).at(dc - 1) = mover |
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92
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if is-pawn and ep != none and dc == ep.at(0) and dr == ep.at(1) { |
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let captured-row = if turn == "white" { dr + 1 } else { dr - 1 } |
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94
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new-grid.at(captured-row - 1).at(dc - 1) = "." |
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95
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} |
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96
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if not is-in-check(new-grid, turn) { return true } |
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97
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} |
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98
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} |
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99
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} |
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100
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101
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let enemy = if turn == "white" { "black" } else { "white" } |
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102
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let options = if turn == "white" { |
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103
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(("K", 8, (6, 7), (6, 7)), ("Q", 8, (2, 3, 4), (3, 4))) |
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} else { |
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105
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(("k", 1, (6, 7), (6, 7)), ("q", 1, (2, 3, 4), (3, 4))) |
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106
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} |
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107
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108
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for (flag, row, empty, check) in options { |
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109
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if castles.contains(flag) and can-castle(grid, row, empty, check, enemy) { return true } |
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110
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} |
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111
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112
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false |
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113
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} |