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Validate_fen : additional checks on kings and on pawns locations. #353

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Validate_fen : additional checks on kings and on pawns locations. #353

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0aa47d4
Check that there is one white/black king and that kings are not neigh…
loloof64 Nov 15, 2022
e95927c
Check that there's no pawn on rank 1 or 8.
loloof64 Nov 15, 2022
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36 changes: 36 additions & 0 deletions __tests__/chess.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1452,6 +1452,42 @@ describe('Validate FEN', () => {
fen: 'rnbqkbnr/1p1ppppp/B1p5/8/6P1/4P3/PPPP1P1P/RNBQK1NR w KQkq g3 0 3',
error_number: 11,
},
{
fen: '8/2K5/8/8/2K1NB2/8/8/8 w - - 96 46',
error_number: 12,
},
{
fen: 'K7/K7/8/8/8/8/8/8 w - - 0 1',
error_number: 12,
},
{
fen: 'k7/k7/8/8/8/8/8/8 w - - 0 1',
error_number: 12,
},
{
fen: '8/8/8/8/8/3k4/2K5/8 w - - 0 1',
error_number: 13,
},
{
fen: '8/8/8/4k3/4K3/8/8/8 b - - 0 1',
error_number: 13,
},
{
fen: '2P5/8/8/3k4/8/2K5/8/8 w - - 0 1',
error_number: 14,
},
{
fen: '8/8/8/3k4/8/2K5/8/5P2 w - - 0 1',
error_number: 14,
},
{
fen: '8/8/8/3k4/8/5K2/8/p7 w - - 0 1',
error_number: 14,
},
{
fen: '6p1/8/8/3k4/8/5K2/8/8 w - - 0 1',
error_number: 14,
},
{
fen: 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1',
error_number: 0,
Expand Down
157 changes: 113 additions & 44 deletions chess.js
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Original file line number Diff line number Diff line change
Expand Up @@ -47,40 +47,40 @@ const PIECE_OFFSETS = {

// prettier-ignore
const ATTACKS = [
20, 0, 0, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0, 0,20, 0,
0,20, 0, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0,20, 0, 0,
0, 0,20, 0, 0, 0, 0, 24, 0, 0, 0, 0,20, 0, 0, 0,
0, 0, 0,20, 0, 0, 0, 24, 0, 0, 0,20, 0, 0, 0, 0,
0, 0, 0, 0,20, 0, 0, 24, 0, 0,20, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0,20, 2, 24, 2,20, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 2,53, 56, 53, 2, 0, 0, 0, 0, 0, 0,
24,24,24,24,24,24,56, 0, 56,24,24,24,24,24,24, 0,
0, 0, 0, 0, 0, 2,53, 56, 53, 2, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0,20, 2, 24, 2,20, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0,20, 0, 0, 24, 0, 0,20, 0, 0, 0, 0, 0,
0, 0, 0,20, 0, 0, 0, 24, 0, 0, 0,20, 0, 0, 0, 0,
0, 0,20, 0, 0, 0, 0, 24, 0, 0, 0, 0,20, 0, 0, 0,
0,20, 0, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0,20, 0, 0,
20, 0, 0, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0, 0,20
20, 0, 0, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0, 0, 20, 0,
0, 20, 0, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0, 20, 0, 0,
0, 0, 20, 0, 0, 0, 0, 24, 0, 0, 0, 0, 20, 0, 0, 0,
0, 0, 0, 20, 0, 0, 0, 24, 0, 0, 0, 20, 0, 0, 0, 0,
0, 0, 0, 0, 20, 0, 0, 24, 0, 0, 20, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 20, 2, 24, 2, 20, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 2, 53, 56, 53, 2, 0, 0, 0, 0, 0, 0,
24, 24, 24, 24, 24, 24, 56, 0, 56, 24, 24, 24, 24, 24, 24, 0,
0, 0, 0, 0, 0, 2, 53, 56, 53, 2, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 20, 2, 24, 2, 20, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 20, 0, 0, 24, 0, 0, 20, 0, 0, 0, 0, 0,
0, 0, 0, 20, 0, 0, 0, 24, 0, 0, 0, 20, 0, 0, 0, 0,
0, 0, 20, 0, 0, 0, 0, 24, 0, 0, 0, 0, 20, 0, 0, 0,
0, 20, 0, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0, 20, 0, 0,
20, 0, 0, 0, 0, 0, 0, 24, 0, 0, 0, 0, 0, 0, 20
];

// prettier-ignore
const RAYS = [
17, 0, 0, 0, 0, 0, 0, 16, 0, 0, 0, 0, 0, 0, 15, 0,
0, 17, 0, 0, 0, 0, 0, 16, 0, 0, 0, 0, 0, 15, 0, 0,
0, 0, 17, 0, 0, 0, 0, 16, 0, 0, 0, 0, 15, 0, 0, 0,
0, 0, 0, 17, 0, 0, 0, 16, 0, 0, 0, 15, 0, 0, 0, 0,
0, 0, 0, 0, 17, 0, 0, 16, 0, 0, 15, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 17, 0, 16, 0, 15, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 17, 16, 15, 0, 0, 0, 0, 0, 0, 0,
1, 1, 1, 1, 1, 1, 1, 0, -1, -1, -1,-1, -1, -1, -1, 0,
0, 0, 0, 0, 0, 0,-15,-16,-17, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0,-15, 0,-16, 0,-17, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0,-15, 0, 0,-16, 0, 0,-17, 0, 0, 0, 0, 0,
0, 0, 0,-15, 0, 0, 0,-16, 0, 0, 0,-17, 0, 0, 0, 0,
0, 0,-15, 0, 0, 0, 0,-16, 0, 0, 0, 0,-17, 0, 0, 0,
0,-15, 0, 0, 0, 0, 0,-16, 0, 0, 0, 0, 0,-17, 0, 0,
-15, 0, 0, 0, 0, 0, 0,-16, 0, 0, 0, 0, 0, 0,-17
17, 0, 0, 0, 0, 0, 0, 16, 0, 0, 0, 0, 0, 0, 15, 0,
0, 17, 0, 0, 0, 0, 0, 16, 0, 0, 0, 0, 0, 15, 0, 0,
0, 0, 17, 0, 0, 0, 0, 16, 0, 0, 0, 0, 15, 0, 0, 0,
0, 0, 0, 17, 0, 0, 0, 16, 0, 0, 0, 15, 0, 0, 0, 0,
0, 0, 0, 0, 17, 0, 0, 16, 0, 0, 15, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 17, 0, 16, 0, 15, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 17, 16, 15, 0, 0, 0, 0, 0, 0, 0,
1, 1, 1, 1, 1, 1, 1, 0, -1, -1, -1, -1, -1, -1, -1, 0,
0, 0, 0, 0, 0, 0, -15, -16, -17, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, -15, 0, -16, 0, -17, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, -15, 0, 0, -16, 0, 0, -17, 0, 0, 0, 0, 0,
0, 0, 0, -15, 0, 0, 0, -16, 0, 0, 0, -17, 0, 0, 0, 0,
0, 0, -15, 0, 0, 0, 0, -16, 0, 0, 0, 0, -17, 0, 0, 0,
0, -15, 0, 0, 0, 0, 0, -16, 0, 0, 0, 0, 0, -17, 0, 0,
-15, 0, 0, 0, 0, 0, 0, -16, 0, 0, 0, 0, 0, 0, -17
];

const SHIFTS = { p: 0, n: 1, b: 2, r: 3, q: 4, k: 5 }
Expand All @@ -106,13 +106,13 @@ const RANK_8 = 0

// prettier-ignore
const SQUARE_MAP = {
a8: 0, b8: 1, c8: 2, d8: 3, e8: 4, f8: 5, g8: 6, h8: 7,
a7: 16, b7: 17, c7: 18, d7: 19, e7: 20, f7: 21, g7: 22, h7: 23,
a6: 32, b6: 33, c6: 34, d6: 35, e6: 36, f6: 37, g6: 38, h6: 39,
a5: 48, b5: 49, c5: 50, d5: 51, e5: 52, f5: 53, g5: 54, h5: 55,
a4: 64, b4: 65, c4: 66, d4: 67, e4: 68, f4: 69, g4: 70, h4: 71,
a3: 80, b3: 81, c3: 82, d3: 83, e3: 84, f3: 85, g3: 86, h3: 87,
a2: 96, b2: 97, c2: 98, d2: 99, e2: 100, f2: 101, g2: 102, h2: 103,
a8: 0, b8: 1, c8: 2, d8: 3, e8: 4, f8: 5, g8: 6, h8: 7,
a7: 16, b7: 17, c7: 18, d7: 19, e7: 20, f7: 21, g7: 22, h7: 23,
a6: 32, b6: 33, c6: 34, d6: 35, e6: 36, f6: 37, g6: 38, h6: 39,
a5: 48, b5: 49, c5: 50, d5: 51, e5: 52, f5: 53, g5: 54, h5: 55,
a4: 64, b4: 65, c4: 66, d4: 67, e4: 68, f4: 69, g4: 70, h4: 71,
a3: 80, b3: 81, c3: 82, d3: 83, e3: 84, f3: 85, g3: 86, h3: 87,
a2: 96, b2: 97, c2: 98, d2: 99, e2: 100, f2: 101, g2: 102, h2: 103,
a1: 112, b1: 113, c1: 114, d1: 115, e1: 116, f1: 117, g1: 118, h1: 119
};

Expand Down Expand Up @@ -404,11 +404,6 @@ export const Chess = function (fen) {
return true
}

/* TODO: this function is pretty much crap - it validates structure but
* completely ignores content (e.g. doesn't verify that each side has a king)
* ... we should rewrite this, and ditch the silly error_number field while
* we're at it
*/
function validate_fen(fen) {
var errors = {
0: 'No errors.',
Expand All @@ -422,11 +417,24 @@ export const Chess = function (fen) {
8: '1st field (piece positions) is invalid [consecutive numbers].',
9: '1st field (piece positions) is invalid [invalid piece].',
10: '1st field (piece positions) is invalid [row too large].',
11: 'Illegal en-passant square',
11: '4th field (en-passant square) is invalid [illegal value].',
12: '1st field (piece positions) is invalid [illegal kings count].',
13: '1st field (piece positions) is invalid [kings on neighbour cells].',
14: '1st field (piece positions) is invalid [pawn on rank 1/8].',
}

/* 1st criterion: 6 space-seperated fields? */
var tokens = fen.split(/\s+/)

/* Empty board is valid */
if (
tokens[0] === '8/8/8/8/8/8/8/8' &&
tokens[2] === '-' &&
tokens[3] === '-'
) {
return { valid: true, error_number: 0, error: errors[0] }
}

/* 1st criterion: 6 space-seperated fields? */
if (tokens.length !== 6) {
return { valid: false, error_number: 1, error: errors[1] }
}
Expand Down Expand Up @@ -495,6 +503,67 @@ export const Chess = function (fen) {
return { valid: false, error_number: 11, error: errors[11] }
}

/* Is there exactly one white king and one black king ? */
var wk_count = 0
var bk_count = 0

for (var i = 0, l = tokens[0].length; i < l; i++) {
if (tokens[0][i] === 'K') {
wk_count += 1
} else if (tokens[0][i] === 'k') {
bk_count += 1
}
}
if (wk_count > 1 || bk_count > 1) {
return { valid: false, error_number: 12, error: errors[12] }
}

/* Are white and black kings on neighbour cells ? */
var wk_square = [-1, -1]
var bk_square = [-1, -1]

var lines = tokens[0].split('/')

for (var row = 0; row < lines.length; row++) {
var line = lines[row]
var lineArr = line.split('')

var file = 0
/* Row index is reversed, but that does not matter here for us. */
for (var col = 0; col < lineArr.length; col++) {
var elem = lineArr[col]
if (elem.match(/\d/)) {
var digit = elem.charCodeAt(0) - '0'.charCodeAt(0)
file += digit
} else {
if (elem === 'K') {
wk_square[0] = row
wk_square[1] = file
} else if (elem === 'k') {
bk_square[0] = row
bk_square[1] = file
}
file++
}
}
}
let abs_dy = Math.abs(wk_square[0] - bk_square[0])
let abs_dx = Math.abs(wk_square[1] - bk_square[1])

if (abs_dx <= 1 && abs_dy <= 1) {
return { valid: false, error_number: 13, error: errors[13] }
}

/* pawn on rank 1 / rank 8 ? */
if (
lines[0].includes('P') ||
lines[0].includes('p') ||
lines[7].includes('P') ||
lines[7].includes('p')
) {
return { valid: false, error_number: 14, error: errors[14] }
}

/* everything's okay! */
return { valid: true, error_number: 0, error: errors[0] }
}
Expand Down
4 changes: 1 addition & 3 deletions package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,7 @@
"main": "chess.js",
"homepage": "https://github.com/jhlywa/chess.js",
"author": "Jeff Hlywa <[email protected]>",
"keywords": [
"chess"
],
"keywords": ["chess"],
"repository": {
"type": "git",
"url": "https://github.com/jhlywa/chess.js.git"
Expand Down