impl/typescript.ts

import { type ToleranceCheck } from "./manufacturing_tolerance_check_types.ts";

const LIMIT = 1_000_000_000_000;

function micrometres(name: string, value: number): number {
  if (!Number.isInteger(value) || value > LIMIT || value < -LIMIT) {
    throw new RangeError(`${name} must be a whole number of micrometres within ±10^12, received ${value}`);
  }
  return value;
}

/**
 * Check a measurement against nominal plus its upper and lower deviations.
 *
 * The deviations are signed and independent, so a tolerance band that lies
 * wholly above or below nominal (an H7 hole, a g6 shaft) is checked correctly;
 * a symmetric band is just `+t, -t`.
 */
export function checkTolerance(measured: number, nominal: number, upperDeviation: number, lowerDeviation: number): ToleranceCheck {
  micrometres("measured", measured);
  micrometres("nominal", nominal);
  micrometres("upperDeviation", upperDeviation);
  micrometres("lowerDeviation", lowerDeviation);
  if (lowerDeviation > upperDeviation) {
    throw new RangeError(
      `lowerDeviation must not be greater than upperDeviation, received ${lowerDeviation} and ${upperDeviation}`,
    );
  }
  const lowerLimit = nominal + lowerDeviation;
  const upperLimit = nominal + upperDeviation;
  const deviation = measured - nominal;
  if (measured > upperLimit) {
    return { passed: false, status: "above", deviation, lowerLimit, upperLimit, outBy: measured - upperLimit };
  }
  if (measured < lowerLimit) {
    return { passed: false, status: "below", deviation, lowerLimit, upperLimit, outBy: lowerLimit - measured };
  }
  return { passed: true, status: "within", deviation, lowerLimit, upperLimit, outBy: 0 };
}