allowsEnPassant()

function allowsEnPassant(piece, movement, targetColumn, targetRow) {
    // this is utter garbage
    // don't look at it

    var lastMove = moveHistory[moveHistory.length - 1];

    if (lastMove != null) {
        var lastPiece = new ChessPiece(lastMove.piece.type.nameID, lastMove.piece.colour, lastMove.origin[0], lastMove.origin[1], true);

        if (enPassantTargets.includes(lastPiece.type.nameID)) {
            if (liesBetween([lastMove.origin[0], lastMove.origin[1]], [targetColumn, targetRow], [lastMove.target[0], lastMove.target[1]], true)) {
                return true;
            }
        }
    }

    return false;
}

function liesBetween(pivotA, cell, pivotB, strict) {
    if (strict && (pivotA.equals(cell) || pivotB.equals(cell))) {
        return false;
    }

    return pivotA[0] == cell[0] && pivotB[0] == cell[0] && sameSign(pivotA[1] - cell[1], cell[1] - pivotB[1]) ||
           pivotA[1] == cell[1] && pivotB[1] == cell[1] && sameSign(pivotA[0] - cell[0], cell[0] - pivotB[0]);
}

function sameSign(a, b) {
    return a <= 0 && b <= 0 || a >= 0 && b >= 0;
}