fillNumber.js

import { Set } from 'immutable';
/**
 * give the coordinate update the current board with a number choice
 * @param x
 * @param y
 * @param number
 * @param fill whether to set or unset
 * @param board the immutable board given to change
 */
function updateBoardWithNumber({
  x, y, number, fill = true, board,
}) {
  let cell = board.get('puzzle').getIn([x, y]);
  // delete its notes
  cell = cell.delete('notes');
  // set or unset its value depending on `fill`
  cell = fill ? cell.set('value', number) : cell.delete('value');
  const increment = fill ? 1 : -1;
  // update the current group choices
  const rowPath = ['choices', 'rows', x, number];
  const columnPath = ['choices', 'columns', y, number];
  const squarePath = ['choices', 'squares',
    ((Math.floor(x / 3)) * 3) + Math.floor(y / 3), number];
  return board.setIn(rowPath, board.getIn(rowPath) + increment)
    .setIn(columnPath, board.getIn(columnPath) + increment)
    .setIn(squarePath, board.getIn(squarePath) + increment)
    .setIn(['puzzle', x, y], cell);
}

class Game extends Compoent {
...  
  // fill currently selected cell with number
  fillNumber = (number) => {
    let { board } = this.state;
    const selectedCell = this.getSelectedCell();
    // no-op if nothing is selected
    if (!selectedCell) return;
    const prefilled = selectedCell.get('prefilled');
    // no-op if it is refilled
    if (prefilled) return;
    const { x, y } = board.get('selected');
    const currentValue = selectedCell.get('value');
    // remove the current value and update the game state
    if (currentValue) {
      board = updateBoardWithNumber({
        x, y, number: currentValue, fill: false, board: this.state.board,
      });
    }
    // update to new number if any
    const setNumber = currentValue !== number && number;
    if (setNumber) {
      board = updateBoardWithNumber({
        x, y, number, fill: true, board,
      });
    }
    this.setState({ board });
  };

  addNumberAsNote = (number) => {
    let { board } = this.state;
    let selectedCell = this.getSelectedCell();
    // no-op if nothing is selected
    if (!selectedCell) return;
    const prefilled = selectedCell.get('prefilled');
    // no-op if it is refilled
    if (prefilled) return;
    const { x, y } = board.get('selected');
    let notes = selectedCell.get('notes') || Set();
    if (notes.has(number)) {
      notes = notes.delete(number);
    } else {
      notes = notes.add(number);
    }
    selectedCell = selectedCell.set('notes', notes);
    selectedCell = selectedCell.delete('value');
    board = board.setIn(['puzzle', x, y], selectedCell);
    this.updateBoard(board);
  };
...
}