ChessPositionAnalyzer.js

// Piece values
const piece = {
    "P": 100,
    "N": 280,
    "B": 320,
    "R": 479,
    "Q": 929,
    "K": 60000
};

// Piece-Square Tables (PSTs)
const pst = {
    'P': [
        0, 0, 0, 0, 0, 0, 0, 0,
        78, 83, 86, 73, 102, 82, 85, 90,
        7, 29, 21, 44, 40, 31, 44, 7,
        -17, 16, -2, 15, 14, 0, 15, -13,
        -26, 3, 10, 9, 6, 1, 0, -23,
        -22, 9, 5, -11, -10, -2, 3, -19,
        -31, 8, -7, -37, -36, -14, 3, -31,
        0, 0, 0, 0, 0, 0, 0, 0
    ],
    'N': [
        -66, -53, -75, -75, -10, -55, -58, -70,
        -3, -6, 100, -36, 4, 62, -4, -14,
        10, 67, 1, 74, 73, 27, 62, -2,
        24, 24, 45, 37, 33, 41, 25, 17,
        -1, 5, 31, 21, 22, 35, 2, 0,
        -18, 10, 13, 22, 18, 15, 11, -14,
        -23, -15, 2, 0, 2, 0, -23, -20,
        -74, -23, -26, -24, -19, -35, -22, -69
    ],
    'B': [
        -59, -78, -82, -76, -23, -107, -37, -50,
        -11, 20, 35, -42, -39, 31, 2, -22,
        -9, 39, -32, 41, 52, -10, 28, -14,
        25, 17, 20, 34, 26, 25, 15, 10,
        13, 10, 17, 23, 17, 16, 0, 7,
        14, 25, 24, 15, 8, 25, 20, 15,
        19, 20, 11, 6, 7, 6, 20, 16,
        -7, 2, -15, -12, -14, -15, -10, -10
    ],
    'R': [
        35, 29, 33, 4, 37, 33, 56, 50,
        55, 29, 56, 67, 55, 62, 34, 60,
        19, 35, 28, 33, 45, 27, 25, 15,
        0, 5, 16, 13, 18, -4, -9, -6,
        -28, -35, -16, -21, -13, -29, -46, -30,
        -42, -28, -42, -25, -25, -35, -26, -46,
        -53, -38, -31, -26, -29, -43, -44, -53,
        -30, -24, -18, 5, -2, -18, -31, -32
    ],
    'Q': [
        6, 1, -8, -104, 69, 24, 88, 26,
        14, 32, 60, -10, 20, 76, 57, 24,
        -2, 43, 32, 60, 72, 63, 43, 2,
        1, -16, 22, 17, 25, 20, -13, -6,
        -14, -15, -2, -5, -1, -10, -20, -22,
        -30, -6, -13, -11, -16, -11, -16, -27,
        -36, -18, 0, -19, -15, -15, -21, -38,
        -39, -30, -31, -13, -31, -36, -34, -42
    ],
    'K': [
        4, 54, 47, -99, -99, 60, 83, -62,
        -32, 10, 55, 56, 56, 55, 10, 3,
        -62, 12, -57, 44, -67, 28, 37, -31,
        -55, 50, 11, -4, -19, 13, 0, -49,
        -55, -43, -52, -28, -51, -47, -8, -50,
        -47, -42, -43, -79, -64, -32, -29, -32,
        -4, 3, -14, -50, -57, -18, 13, 4,
        17, 30, -3, -14, 6, -1, 40, 18
    ]
};

// Function to parse a FEN string and calculate the advantage
function calculateAdvantage(fen) {
    const pieceValues = {
        'P': piece['P'], 'N': piece['N'], 'B': piece['B'],
        'R': piece['R'], 'Q': piece['Q'], 'K': piece['K'],
        'p': piece['P'], 'n': piece['N'], 'b': piece['B'],
        'r': piece['R'], 'q': piece['Q'], 'k': piece['K']
    };

    // Convert FEN to 8x8 board
    const board = fen.split(' ')[0]
        .split('/')
        .map(row => row.replace(/(\d)/g, d => ' '.repeat(Number(d)))  // Replace numbers with spaces
        .split(''))  // Split into characters
        .flat();  // Flatten into a single array

    let materialWhite = 0;
    let materialBlack = 0;
    let positionWhite = 0;
    let positionBlack = 0;

    for (let i = 0; i < board.length; i++) {
        const square = board[i];
        if (square !== ' ') {
            const value = pieceValues[square];
            const pstValue = getPstValue(square, i);
            if (square === square.toUpperCase()) {
                materialWhite += value;
                positionWhite += pstValue;
            } else {
                materialBlack += value;
                positionBlack += pstValue;
            }
        }
    }

    const materialAdvantage = materialWhite - materialBlack;
    const positionAdvantage = positionWhite - positionBlack;

    const combinedAdvantage = materialAdvantage + positionAdvantage;

    return combinedAdvantage;
}

// Get PST value based on piece and position index
function getPstValue(piece, squareIndex) {
    // Index adjustment for black pieces
    const adjustedIndex = piece === piece.toUpperCase() ? squareIndex : 63 - squareIndex;
    return pst[piece.toUpperCase()][adjustedIndex];
}

// Test FEN
const fen = 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1';
console.log(calculateAdvantage(fen));