drive-between-the-lines/src/sim/kia.test.ts

import { describe, expect, it } from 'vitest';
import { applyWear, freshCondition, repair, SUBSYSTEMS, type CarCondition } from './car';
import { isWrittenOff, KIA_LAND_LOSS, replacementCar } from './kia';
import { createFront, applyMissionImpact, depthAt } from './regions';
import { accept, createQuests, failQuest, type Offer } from './quests';

const at = (chassis: number): CarCondition => ({
  level: { engine: 0.5, tires: 0.5, chassis },
  ceiling: { engine: 0.8, tires: 0.8, chassis: 0.8 },
});

describe('being written off', () => {
  it('is the chassis that kills you, not the engine or the tyres', () => {
    expect(isWrittenOff(at(0))).toBe(true);
    expect(isWrittenOff(at(0.01))).toBe(false);
    expect(
      isWrittenOff({
        level: { engine: 0, tires: 0, chassis: 0.4 },
        ceiling: { engine: 1, tires: 1, chassis: 1 },
      }),
    ).toBe(false);
  });

  it('is reachable — a car can actually be driven into the ground', () => {
    let c = freshCondition();
    for (let i = 0; i < 400 && !isWrittenOff(c); i++) {
      c = applyWear(c, { dt: 1 / 60, distance: 3, throttle: 1, impactForce: 2.5e6 });
    }
    expect(isWrittenOff(c)).toBe(true);
  });
});

describe('the replacement car', () => {
  it('is handed over running, or it would kill you again immediately', () => {
    const next = replacementCar(at(0));
    expect(isWrittenOff(next)).toBe(false);
    for (const part of SUBSYSTEMS) {
      expect(next.level[part]).toBeCloseTo(next.ceiling[part], 9);
    }
  });

  it('is always worse than the one you wrote off', () => {
    const before = at(0);
    const next = replacementCar(before);
    for (const part of SUBSYSTEMS) {
      expect(next.ceiling[part]).toBeLessThan(before.ceiling[part]);
    }
  });

  it('ratchets down over a long campaign without ever becoming undriveable', () => {
    let c = freshCondition();
    let previous = 1;
    for (let death = 0; death < 40; death++) {
      c = replacementCar({ ...c, level: { ...c.level, chassis: 0 } });
      expect(c.ceiling.chassis).toBeLessThanOrEqual(previous);
      previous = c.ceiling.chassis;
      // Whatever else is true, you can always get back on the road.
      expect(isWrittenOff(c)).toBe(false);
      expect(repair(c, 99).condition.level.chassis).toBeGreaterThan(0);
    }
    // Twenty-odd deaths in and the car is a genuinely miserable thing to drive.
    expect(previous).toBeLessThan(0.35);
  });
});

describe('what a death costs', () => {
  it('gives ground back to the enemy', () => {
    const front = createFront(11, 400, { x: 0, z: 0 });
    const before = front.boundaries.liberated;
    applyMissionImpact(front, -KIA_LAND_LOSS);
    expect(front.boundaries.liberated).toBeLessThan(before);
  });

  it('loses the job in hand without counting it as a run', () => {
    const quests = createQuests();
    const offer = {
      id: 1,
      type: 'supply',
      targetNode: 4,
      novel: true,
      route: { nodes: [0, 4], segments: [0], length: 900 },
      intel: { worst: 'clear', unknownCount: 1, stalest: null },
      reward: 0.3,
      impact: 15,
    } as unknown as Offer;
    accept(quests, offer, { nodeId: 0, x: 0, z: 0, hutX: 0, hutZ: 0, name: 'Anvil' });

    const lost = failQuest(quests);
    expect(lost?.type).toBe('supply');
    expect(quests.active).toBeNull();
    expect(quests.completed).toBe(0);
    expect(quests.failed).toBe(1);
    expect(quests.funds).toBe(0);
  });

  it('is a setback, not a campaign reversal', () => {
    // Sanity on the scale: a death should cost less ground than a couple of
    // decent missions win, or dying once undoes an evening's work.
    const front = createFront(3, 400, { x: 0, z: 0 });
    const start = depthAt(front, 0, 0);
    void start;
    applyMissionImpact(front, 40);
    const won = front.boundaries.liberated;
    applyMissionImpact(front, -KIA_LAND_LOSS);
    expect(front.boundaries.liberated).toBeLessThan(won);
    expect(front.boundaries.liberated).toBeGreaterThan(won - 40);
  });
});