source: node_modules/recharts/es6/util/scale/getNiceTickValues.js@ a762898

/**
 * @fileOverview calculate tick values of scale
 * @author xile611, arcthur
 * @date 2015-09-17
 */
import Decimal from 'decimal.js-light';
import { getDigitCount, rangeStep } from './util/arithmetic';
/**
 * Calculate a interval of a minimum value and a maximum value
 *
 * @param  {Number} min       The minimum value
 * @param  {Number} max       The maximum value
 * @return {Array} An interval
 */
export var getValidInterval = _ref => {
  var [min, max] = _ref;
  var [validMin, validMax] = [min, max];

  // exchange
  if (min > max) {
    [validMin, validMax] = [max, min];
  }
  return [validMin, validMax];
};

/**
 * Calculate the step which is easy to understand between ticks, like 10, 20, 25
 *
 * @param  roughStep        The rough step calculated by dividing the difference by the tickCount
 * @param  allowDecimals    Allow the ticks to be decimals or not
 * @param  correctionFactor A correction factor
 * @return The step which is easy to understand between two ticks
 */
export var getFormatStep = (roughStep, allowDecimals, correctionFactor) => {
  if (roughStep.lte(0)) {
    return new Decimal(0);
  }
  var digitCount = getDigitCount(roughStep.toNumber());
  // The ratio between the rough step and the smallest number which has a bigger
  // order of magnitudes than the rough step
  var digitCountValue = new Decimal(10).pow(digitCount);
  var stepRatio = roughStep.div(digitCountValue);
  // When an integer and a float multiplied, the accuracy of result may be wrong
  var stepRatioScale = digitCount !== 1 ? 0.05 : 0.1;
  var amendStepRatio = new Decimal(Math.ceil(stepRatio.div(stepRatioScale).toNumber())).add(correctionFactor).mul(stepRatioScale);
  var formatStep = amendStepRatio.mul(digitCountValue);
  return allowDecimals ? new Decimal(formatStep.toNumber()) : new Decimal(Math.ceil(formatStep.toNumber()));
};

/**
 * calculate the ticks when the minimum value equals to the maximum value
 *
 * @param  value         The minimum value which is also the maximum value
 * @param  tickCount     The count of ticks
 * @param  allowDecimals Allow the ticks to be decimals or not
 * @return array of ticks
 */
export var getTickOfSingleValue = (value, tickCount, allowDecimals) => {
  var step = new Decimal(1);
  // calculate the middle value of ticks
  var middle = new Decimal(value);
  if (!middle.isint() && allowDecimals) {
    var absVal = Math.abs(value);
    if (absVal < 1) {
      // The step should be a float number when the difference is smaller than 1
      step = new Decimal(10).pow(getDigitCount(value) - 1);
      middle = new Decimal(Math.floor(middle.div(step).toNumber())).mul(step);
    } else if (absVal > 1) {
      // Return the maximum integer which is smaller than 'value' when 'value' is greater than 1
      middle = new Decimal(Math.floor(value));
    }
  } else if (value === 0) {
    middle = new Decimal(Math.floor((tickCount - 1) / 2));
  } else if (!allowDecimals) {
    middle = new Decimal(Math.floor(value));
  }
  var middleIndex = Math.floor((tickCount - 1) / 2);
  var ticks = [];
  for (var i = 0; i < tickCount; i++) {
    ticks.push(middle.add(new Decimal(i - middleIndex).mul(step)).toNumber());
  }
  return ticks;
};

/**
 * Calculate the step
 *
 * @param  min              The minimum value of an interval
 * @param  max              The maximum value of an interval
 * @param  tickCount        The count of ticks
 * @param  allowDecimals    Allow the ticks to be decimals or not
 * @param  correctionFactor A correction factor
 * @return The step, minimum value of ticks, maximum value of ticks
 */
var _calculateStep = function calculateStep(min, max, tickCount, allowDecimals) {
  var correctionFactor = arguments.length > 4 && arguments[4] !== undefined ? arguments[4] : 0;
  // dirty hack (for recharts' test)
  if (!Number.isFinite((max - min) / (tickCount - 1))) {
    return {
      step: new Decimal(0),
      tickMin: new Decimal(0),
      tickMax: new Decimal(0)
    };
  }

  // The step which is easy to understand between two ticks
  var step = getFormatStep(new Decimal(max).sub(min).div(tickCount - 1), allowDecimals, correctionFactor);

  // A medial value of ticks
  var middle;

  // When 0 is inside the interval, 0 should be a tick
  if (min <= 0 && max >= 0) {
    middle = new Decimal(0);
  } else {
    // calculate the middle value
    middle = new Decimal(min).add(max).div(2);
    // minus modulo value
    middle = middle.sub(new Decimal(middle).mod(step));
  }
  var belowCount = Math.ceil(middle.sub(min).div(step).toNumber());
  var upCount = Math.ceil(new Decimal(max).sub(middle).div(step).toNumber());
  var scaleCount = belowCount + upCount + 1;
  if (scaleCount > tickCount) {
    // When more ticks need to cover the interval, step should be bigger.
    return _calculateStep(min, max, tickCount, allowDecimals, correctionFactor + 1);
  }
  if (scaleCount < tickCount) {
    // When less ticks can cover the interval, we should add some additional ticks
    upCount = max > 0 ? upCount + (tickCount - scaleCount) : upCount;
    belowCount = max > 0 ? belowCount : belowCount + (tickCount - scaleCount);
  }
  return {
    step,
    tickMin: middle.sub(new Decimal(belowCount).mul(step)),
    tickMax: middle.add(new Decimal(upCount).mul(step))
  };
};

/**
 * Calculate the ticks of an interval. Ticks can appear outside the interval
 * if it makes them more rounded and nice.
 *
 * @param tuple of [min,max] min: The minimum value, max: The maximum value
 * @param tickCount     The count of ticks
 * @param allowDecimals Allow the ticks to be decimals or not
 * @return array of ticks
 */
export { _calculateStep as calculateStep };
export var getNiceTickValues = function getNiceTickValues(_ref2) {
  var [min, max] = _ref2;
  var tickCount = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 6;
  var allowDecimals = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : true;
  // More than two ticks should be return
  var count = Math.max(tickCount, 2);
  var [cormin, cormax] = getValidInterval([min, max]);
  if (cormin === -Infinity || cormax === Infinity) {
    var _values = cormax === Infinity ? [cormin, ...Array(tickCount - 1).fill(Infinity)] : [...Array(tickCount - 1).fill(-Infinity), cormax];
    return min > max ? _values.reverse() : _values;
  }
  if (cormin === cormax) {
    return getTickOfSingleValue(cormin, tickCount, allowDecimals);
  }

  // Get the step between two ticks
  var {
    step,
    tickMin,
    tickMax
  } = _calculateStep(cormin, cormax, count, allowDecimals, 0);
  var values = rangeStep(tickMin, tickMax.add(new Decimal(0.1).mul(step)), step);
  return min > max ? values.reverse() : values;
};

/**
 * Calculate the ticks of an interval.
 * Ticks will be constrained to the interval [min, max] even if it makes them less rounded and nice.
 *
 * @param tuple of [min,max] min: The minimum value, max: The maximum value
 * @param tickCount     The count of ticks. This function may return less than tickCount ticks if the interval is too small.
 * @param allowDecimals Allow the ticks to be decimals or not
 * @return array of ticks
 */
export var getTickValuesFixedDomain = function getTickValuesFixedDomain(_ref3, tickCount) {
  var [min, max] = _ref3;
  var allowDecimals = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : true;
  // More than two ticks should be return
  var [cormin, cormax] = getValidInterval([min, max]);
  if (cormin === -Infinity || cormax === Infinity) {
    return [min, max];
  }
  if (cormin === cormax) {
    return [cormin];
  }
  var count = Math.max(tickCount, 2);
  var step = getFormatStep(new Decimal(cormax).sub(cormin).div(count - 1), allowDecimals, 0);
  var values = [...rangeStep(new Decimal(cormin), new Decimal(cormax), step), cormax];
  if (allowDecimals === false) {
    /*
     * allowDecimals is false means that we want to have integer ticks.
     * The step is guaranteed to be an integer in the code above which is great start
     * but when the first step is not an integer, it will start stepping from a decimal value anyway.
     * So we need to round all the values to integers after the fact.
     */
    values = values.map(value => Math.round(value));
  }
  return min > max ? values.reverse() : values;
};