impl/typescript.ts

Imports name this capability’s declared dependencies, which fune builds next to it in your project; each one links to its page.

import { roundDiv } from "./math_round_div.ts";  ← from math.round-div ^1.0.0 · built alongside by fune
import { type ChargeableWeight } from "./retail_volumetric_weight_types.ts";

/**
 * The weight a carrier charges on: the greater of actual and volumetric,
 * rounded up to the carrier's billing step.
 *
 * mm³ / (cm³ per kg) is exactly grams, so everything stays in integers.
 */
export function chargeableWeight(
  lengthMm: number,
  widthMm: number,
  heightMm: number,
  actualGrams: number,
  divisor: number,
  roundUpToGrams: number,
): ChargeableWeight {
  for (const d of [lengthMm, widthMm, heightMm]) {
    if (!Number.isInteger(d) || d < 1) throw new RangeError(`dimensions must be 1 mm or more, received ${d}`);
  }
  if (!Number.isInteger(actualGrams) || actualGrams < 0) {
    throw new RangeError(`actualGrams must not be negative, received ${actualGrams}`);
  }
  if (!Number.isInteger(divisor) || divisor < 1) throw new RangeError(`divisor must be 1 or more, received ${divisor}`);
  if (!Number.isInteger(roundUpToGrams) || roundUpToGrams < 1) {
    throw new RangeError(`roundUpToGrams must be 1 or more, received ${roundUpToGrams}`);
  }
  const volumetricGrams = roundDiv(lengthMm * widthMm * heightMm, divisor, "up");
  const heavier = Math.max(actualGrams, volumetricGrams);
  return {
    actualGrams,
    volumetricGrams,
    chargeableGrams: roundDiv(heavier, roundUpToGrams, "up") * roundUpToGrams,
    basis: volumetricGrams > actualGrams ? "volumetric" : "actual",
  };
}