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chessy.js
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/**
* Copyright (c) 2019, Luciano Ropero <lropero@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
const COLORS = ['black', 'white']
const OFFSETS = {
bishop: [-17, -15, 17, 15],
king: [-17, -16, -15, 1, 17, 16, 15, -1],
knight: [-18, -33, -31, -14, 18, 33, 31, 14],
pawn: {
black: [16, 32, 17, 15],
white: [-16, -32, -17, -15]
},
queen: [-17, -16, -15, 1, 17, 16, 15, -1],
rook: [-16, 1, 16, -1]
}
/* eslint-disable */
const SQUARES = {
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
}
/* eslint-enable */
const fenToBoard = (fen) => {
if (typeof fen === 'string' && /^[1-8BKNQRbknqr]+\/([1-8BKNPQRbknpqr]+\/){6}[1-8BKNQRbknqr]+(\s[bw]\s(-|K?Q?k?q?)\s(-|[a-h][36])\s\d+\s\d+)?$/.test(fen)) {
const [position, turn = null,, ep = null] = fen.split(' ')
const board = new Array(128)
const charToType = (char) => {
switch (char) {
case 'b': return 'bishop'
case 'k': return 'king'
case 'n': return 'knight'
case 'p': return 'pawn'
case 'q': return 'queen'
case 'r': return 'rook'
}
}
let square = 0
for (const char of position.split('')) {
if (char === '/') {
square += 8
} else if ('0123456789'.indexOf(char) !== -1) {
square += parseInt(char, 10)
} else {
board[square++] = { color: char >= 'a' ? 'black' : 'white', type: charToType(char.toLowerCase()) }
}
}
return { board, ep: ep && ep !== '-' && SQUARES[ep], turn }
}
return { board: [], ep: null, turn: null }
}
const getAttacking = (fen, extra = {}) => {
const attacking = COLORS.reduce((attacking, color) => {
attacking[color] = {}
return attacking
}, {})
const { board, ep, turn } = (Object.keys(extra).length === 3 && extra) || fenToBoard(fen)
if (board.length) {
const sights = getSights(fen, { board })
for (const [index, color] of COLORS.entries()) {
attacking[(extra.threats && COLORS[1 - index]) || color] = Object.keys(sights[color]).reduce((attackingColor, fromAlgebraic) => {
for (const toAlgebraic of sights[color][fromAlgebraic]) {
const enPassant = ep === SQUARES[toAlgebraic] && turn === board[SQUARES[fromAlgebraic]].color.charAt(0) && board[SQUARES[fromAlgebraic]].type === 'pawn'
const piece = board[SQUARES[toAlgebraic]] && board[SQUARES[toAlgebraic]].color !== color
const illegalKingMove = piece && board[SQUARES[fromAlgebraic]].type === 'king' && Object.values(sights[board[SQUARES[toAlgebraic]].color]).reduce((defended, defenses) => [...defended, ...defenses], []).includes(toAlgebraic)
if ((enPassant || piece) && !illegalKingMove) {
if (!attackingColor[extra.threats ? toAlgebraic : fromAlgebraic]) {
attackingColor[extra.threats ? toAlgebraic : fromAlgebraic] = []
}
attackingColor[extra.threats ? toAlgebraic : fromAlgebraic].push(extra.threats ? fromAlgebraic : toAlgebraic)
}
}
return attackingColor
}, {})
}
}
return attacking
}
const getDefending = (fen, extra = {}) => {
const defending = COLORS.reduce((defending, color) => {
defending[color] = {}
return defending
}, {})
const { board } = (Object.keys(extra).includes('board') && extra) || fenToBoard(fen)
if (board.length) {
const sights = getSights(fen, { board })
for (const color of COLORS) {
defending[color] = Object.keys(sights[color]).reduce((defendingColor, fromAlgebraic) => {
for (const toAlgebraic of sights[color][fromAlgebraic]) {
if (board[SQUARES[toAlgebraic]] && board[SQUARES[toAlgebraic]].color === color) {
if (!defendingColor[extra.defenses ? toAlgebraic : fromAlgebraic]) {
defendingColor[extra.defenses ? toAlgebraic : fromAlgebraic] = []
}
defendingColor[extra.defenses ? toAlgebraic : fromAlgebraic].push(extra.defenses ? fromAlgebraic : toAlgebraic)
}
}
return defendingColor
}, {})
}
}
if (extra.defenses) {
return COLORS.reduce((defenses, color) => {
defenses[color] = Object.keys(defending[color]).sort().reduce((defensesColor, fromAlgebraic) => {
defensesColor[fromAlgebraic] = defending[color][fromAlgebraic]
return defensesColor
}, {})
return defenses
}, {})
} else {
return defending
}
}
const getDefenses = (fen, extra = {}) => {
return getDefending(fen, Object.assign({}, extra, { defenses: true }))
}
const getInfo = (fen, algebraics) => {
if (Array.isArray(algebraics)) {
const { board, ep, turn } = fenToBoard(fen)
if (board.length) {
const attacking = getAttacking(fen, { board, ep, turn })
const defending = getDefending(fen, { board, ep, turn })
const defenses = getDefenses(fen, { board, ep, turn })
const sights = getSights(fen, { board, ep, turn })
const threats = getThreats(fen, { board, ep, turn })
return algebraics.sort().reduce((info, algebraic) => {
const piece = board[SQUARES[algebraic]]
if (piece) {
info[algebraic] = {
attacking: Object.assign({}, ...Object.values(attacking))[algebraic] || null,
defending: Object.assign({}, ...Object.values(defending))[algebraic] || null,
defenses: Object.assign({}, ...Object.values(defenses))[algebraic] || null,
piece,
sights: Object.assign({}, ...Object.values(sights))[algebraic] || null,
threats: Object.assign({}, ...Object.values(threats))[algebraic] || null
}
}
return info
}, {})
}
}
return {}
}
const getObscured = (fen) => {
const obscured = COLORS.reduce((obscured, color) => {
obscured[color] = []
return obscured
}, {})
const { board } = fenToBoard(fen)
if (board.length) {
const sights = getSights(fen)
const squares = Object.keys(SQUARES).sort()
for (const color of COLORS) {
obscured[color] = squares.filter((algebraic) => ![].concat(...Object.keys(sights[color])).concat(...Object.values(sights[color])).includes(algebraic))
}
}
return obscured
}
const getSights = (fen, extra = {}) => {
const temp = COLORS.reduce((temp, color) => {
temp[color] = {}
return temp
}, {})
const { board } = (Object.keys(extra).includes('board') && extra) || fenToBoard(fen)
if (board.length) {
for (const [from, piece] of board.entries()) {
if (piece) {
const fromAlgebraic = squareToAlgebraic(from)
if (piece.type === 'pawn') {
for (let i = 2; i < 4; i++) {
const to = from + OFFSETS.pawn[piece.color][i]
if (to & 0x88) continue
if (!temp[piece.color][fromAlgebraic]) {
temp[piece.color][fromAlgebraic] = []
}
temp[piece.color][fromAlgebraic].push(squareToAlgebraic(to))
}
} else {
for (let i = 0; i < OFFSETS[piece.type].length; i++) {
let to = from
while (true) {
to += OFFSETS[piece.type][i]
if (to & 0x88) break
if (!temp[piece.color][fromAlgebraic]) {
temp[piece.color][fromAlgebraic] = []
}
temp[piece.color][fromAlgebraic].push(squareToAlgebraic(to))
if (board[to] || piece.type === 'king' || piece.type === 'knight') break
}
}
}
}
}
}
return COLORS.reduce((sights, color) => {
sights[color] = Object.keys(temp[color]).sort().reduce((sightsColor, fromAlgebraic) => {
sightsColor[fromAlgebraic] = temp[color][fromAlgebraic].sort()
return sightsColor
}, {})
return sights
}, {})
}
const getThreats = (fen, extra = {}) => {
return getAttacking(fen, Object.assign({}, extra, { threats: true }))
}
const squareToAlgebraic = (square) => {
const file = square & 15
const rank = square >> 4
return 'abcdefgh'.substring(file, file + 1) + '87654321'.substring(rank, rank + 1)
}
exports.getAttacking = getAttacking
exports.getDefending = getDefending
exports.getDefenses = getDefenses
exports.getInfo = getInfo
exports.getObscured = getObscured
exports.getSights = getSights
exports.getThreats = getThreats
module.exports = { getAttacking, getDefending, getDefenses, getInfo, getObscured, getSights, getThreats }