Function offsetValue

src/hooks/useOffset.ts:94–171

(values, offset, valueIndex, mode = 'unit')

  // ========================== Offset ==========================
  // Single Value
  const offsetValue: OffsetValue = (values, offset, valueIndex, mode = 'unit') => {
    if (typeof offset === 'number') {
      let nextValue: number;
      const originValue = values[valueIndex];

      // Only used for `dist` mode
      const targetDistValue = originValue + offset;

      // Compare next step value & mark value which is best match
      let potentialValues: number[] = [];
      markList.forEach((mark) => {
        potentialValues.push(mark.value);
      });

      // Min & Max
      potentialValues.push(min, max);

      // In case origin value is align with mark but not with step
      potentialValues.push(formatStepValue(originValue));

      // Put offset step value also
      const sign = offset > 0 ? 1 : -1;

      if (mode === 'unit') {
        potentialValues.push(formatStepValue(originValue + sign * step));
      } else {
        potentialValues.push(formatStepValue(targetDistValue));
      }

      // Find close one
      potentialValues = potentialValues
        .filter((val) => val !== null)
        // Remove reverse value
        .filter((val) => (offset < 0 ? val <= originValue : val >= originValue));

      if (mode === 'unit') {
        // `unit` mode can not contain itself
        potentialValues = potentialValues.filter((val) => val !== originValue);
      }

      const compareValue = mode === 'unit' ? originValue : targetDistValue;

      nextValue = potentialValues[0];
      let valueDist = Math.abs(nextValue - compareValue);

      potentialValues.forEach((potentialValue) => {
        const dist = Math.abs(potentialValue - compareValue);
        if (dist < valueDist) {
          nextValue = potentialValue;
          valueDist = dist;
        }
      });

      // Out of range will back to range
      if (nextValue === undefined) {
        return offset < 0 ? min : max;
      }