edr-platform/apps/edr-freight-api/src/modules/train-scheduling/train-capacity.util.spec.ts

import {
  bookingTrainLengthMeters,
  deriveTrainCapacityFromLocomotive,
  minLocomotiveLimits,
} from './train-capacity.util';

describe('train-capacity.util', () => {
  const nw5 = { lengthMeters: 14, capacityTons: 70 };

  it('derives wagon slots from locomotive length and weight, not a fixed 53', () => {
    const shortLoco = deriveTrainCapacityFromLocomotive(
      { maxPullWeightTons: 2000, maxTrainLengthMeters: 280 },
      [nw5],
    );
    expect(shortLoco.maxWagonSlots).toBe(20); // 280 / 14
    expect(shortLoco.maxWagonSlots).not.toBe(53);

    const heavyLoco = deriveTrainCapacityFromLocomotive(
      { maxPullWeightTons: 2100, maxTrainLengthMeters: 760 },
      [nw5],
    );
    expect(heavyLoco.maxWagonSlots).toBe(30); // min(54, 30) from weight 2100/70
  });

  it('uses shortest wagon type when mixed types are present', () => {
    const longBulk = { lengthMeters: 18, capacityTons: 80 };
    const mixed = deriveTrainCapacityFromLocomotive(
      { maxPullWeightTons: 3500, maxTrainLengthMeters: 760 },
      [nw5, longBulk],
    );
    expect(mixed.maxWagonSlots).toBe(
      Math.min(Math.floor(760 / 14), Math.floor(3500 / 70)),
    );
  });

  it('computes booking length by freight type', () => {
    expect(
      bookingTrainLengthMeters('CONTAINER', 2, { container: 14, bulk: 14 }),
    ).toBe(28);
    expect(bookingTrainLengthMeters('BULK', 3, { container: 14, bulk: 18 })).toBe(54);
  });

  it('extends weight/length caps by the locomotive overage tolerance (fertilizer +90T example)', () => {
    const pw2 = { lengthMeters: 17.066, capacityTons: 70 };
    const derived = deriveTrainCapacityFromLocomotive(
      { maxPullWeightTons: 3500, maxTrainLengthMeters: 760, overageToleranceTons: 90 },
      [pw2],
    );
    expect(derived.maxWeightTons).toBe(3590);
  });

  it('ignores overage tolerance when unset (strict cap, no behavior change)', () => {
    const derived = deriveTrainCapacityFromLocomotive(
      { maxPullWeightTons: 3500, maxTrainLengthMeters: 760 },
      [{ lengthMeters: 14, capacityTons: 70 }],
    );
    expect(derived.maxWeightTons).toBe(3500);
    expect(derived.maxLengthMeters).toBe(760);
  });

  it('takes the weakest locomotive tolerance across a multi-locomotive set', () => {
    const limits = minLocomotiveLimits([
      { maxPullWeightTons: 3500, maxTrainLengthMeters: 760, overageToleranceTons: 90 },
      { maxPullWeightTons: 4000, maxTrainLengthMeters: 760, overageToleranceTons: 20 },
    ]);
    expect(limits?.maxPullWeightTons).toBe(3500);
    expect(limits?.overageToleranceTons).toBe(20);
  });
});