utils.js

/* jshint node: true */

'use strict';

const DEFAULT_PALETTE_OPTIONS = {
  'blackAndWhite': false,
  'greys': 'auto',
  'shades': 'auto',
  'shuffle': false
};

const shuffleArray = (a) => {
  const CUTOFF = a.length % 22 + 1,
    MASK = 0xffffff & a.length << 16 + a.length << 8 + a.length;
  const HASH = (n) => MASK & n << CUTOFF + (n >> 24 - CUTOFF);

return a.slice().sort((x, y) => {
    if (HASH(x) > HASH(y))
      return -1;
    if (HASH(x) < HASH(y))
      return +1;

return 0;
  });
};

const randomiseArray = (a) => {
  const RESULT = a.slice();
  let tmp, x;
  for (let i = 0; i < RESULT.length; i++) {
    x = Math.floor(Math.random() * RESULT.length);
    tmp = RESULT[x];
    RESULT[x] = RESULT[i];
    RESULT[i] = tmp;
  }

return RESULT;
};

const checkPaletteParams = (n, opts) => {
  if (!Number.isInteger(n) || 2 > n)
    return new Error('superscript.Palette: “n” must be an integer ≥ 2');
  for (const i in opts)
    if ('blackAndWhite' === i) {
      if (false !== opts[i] && true !== opts[i])
        return new Error('superscript.Palette: “blackAndWhite” must be either “false” or “true”');
    } else if ('greys' === i) {
      if (false !== opts[i] && true !== opts[i] && 'auto' !== opts[i])
        return new Error('superscript.Palette: “greys” must be either “false”, “true” or “auto”');
    } else if ('shades' === i) {
      if (false !== opts[i] && true !== opts[i] && 'auto' !== opts[i] && (!Number.isInteger(opts[i]) || 1 > opts[i]))
        return new Error('superscript.Palette: “shades” must be either “false”, “true”, “auto” or an integer ≥ 1');
    } else if ('shuffle' === i) {
      if (false !== opts[i] && true !== opts[i] && 'random' !== opts[i])
        return new Error('superscript.Palette: “shuffle” must be either “false”, “true” or “random”');
    } else
      return new Error(`superscript.Palette: “${i}” is not a valid option`);
  if (opts.blackAndWhite && true === opts.greys && 3 > n)
    return new Error('superscript.Palette: “blackAndWhite” and “greys” cannot be both “true” when “n” < 3');
  if (opts.blackAndWhite && true === opts.shades && 4 > n)
    return new Error('superscript.Palette: “blackAndWhite” and “shades” cannot be both “true” when “n” < 4');
  if (opts.shades + (opts.blackAndWhite ? 2 : 0) < n)
    return new Error(`superscript.Palette: the palette is too small to include ${opts.shades} shades${opts.blackAndWhite ? ' plus black and white' : ''}`);

return false;
};

exports.DEFAULT_PALETTE_OPTIONS = DEFAULT_PALETTE_OPTIONS;
exports.shuffleArray = shuffleArray;
exports.randomiseArray = randomiseArray;
exports.checkPaletteParams = checkPaletteParams;