Made of little things.

import assert from 'node:assert/strict';
import test from 'node:test';
import { createSimulation, FIXED_STEP } from '../src/simulation.ts';
const idle = { throttle: 0, steer: 0, brake: false };
function advance(sim, seconds, controls = idle) { for (let i = 0; i < Math.round(seconds / FIXED_STEP); i++) sim.step(FIXED_STEP, controls); }

test('the car climbs the ramp from a standing start at light and full throttle', () => {
  for (const throttle of [0.2, 1]) {
    const sim = createSimulation();
    sim.chassis.position.set(18, 1.1, 5); sim.chassis.aabbNeedsUpdate = true;
    advance(sim, 2);
    let highest = 0, farthest = 5;
    for (let i = 0; i < 12 / FIXED_STEP; i++) {
      sim.step(FIXED_STEP, { ...idle, throttle });
      highest = Math.max(highest, sim.chassis.position.y);
      farthest = Math.min(farthest, sim.chassis.position.z);
    }
    assert.ok(highest > 3 && farthest < -11, `throttle ${throttle}: ramp climb stalled at z=${farthest.toFixed(2)}, height=${highest.toFixed(2)}`);
  }
});

test('all 157 pieces remain stable at rest and suspension supports the chassis', () => {
  const sim = createSimulation(); advance(sim, 8);
  assert.equal(sim.props.length, 157); assert.equal(sim.stats().displaced, 0);
  assert.ok(sim.chassis.position.y > 0.5 && sim.chassis.position.y < 0.8);
  assert.ok(sim.stats().speed < 0.1);
});
test('accelerating into crates transfers momentum and leaves remote structures standing', () => {
  const sim = createSimulation(); advance(sim, 3); advance(sim, 6, { ...idle, throttle: 1 });
  assert.ok(sim.chassis.position.z < -5, 'accelerator moves the car toward the obstacles');
  assert.ok(sim.stats().groups[0] >= 15, 'impact displaces most of the main crate stack');
  assert.ok(sim.stats().groups.slice(1).every(count => count === 0));
  assert.ok(sim.stats().peakImpact > 30);
  for (const prop of sim.props) assert.ok(prop.body.position.y > -0.1 && Number.isFinite(prop.body.velocity.length()));
  sim.rebuild(); advance(sim, 3);
  assert.equal(sim.stats().displaced, 0); assert.equal(sim.stats().peakImpact, 0);
  assert.ok(Math.abs(sim.chassis.position.z - 17) < 0.1);
});
test('left and right steering turn in the expected directions; brakes stop the vehicle', () => {
  for (const steer of [-1, 1]) {
    const sim = createSimulation(); advance(sim, 2); advance(sim, 1.5, { ...idle, throttle: 1, steer });
    assert.ok(sim.chassis.position.x * steer < -3);
    const movingSpeed = sim.stats().speed;
    advance(sim, 2, { ...idle, brake: true });
    assert.ok(sim.stats().speed < movingSpeed * 0.1);
  }
});
test('reverse and recovery work without rebuilding the structures', () => {
  const sim = createSimulation(); advance(sim, 2); advance(sim, 1, { ...idle, throttle: -1 });
  assert.ok(sim.chassis.position.z > 20);
  sim.props[0].body.position.x += 3;
  sim.recover(); advance(sim, 1);
  assert.ok(Math.abs(sim.chassis.position.z - 17) < 0.1);
  assert.ok(sim.stats().displaced >= 1);
});

test('striking the new timber tower and arch brings down their supported pieces', () => {
  for (const [x, z, group, minimum] of [[26, 25, 5, 18], [-10.8, -19, 6, 7]]) {
    const sim = createSimulation();
    sim.chassis.position.set(x, 1.1, z); sim.chassis.aabbNeedsUpdate = true;
    advance(sim, 2); advance(sim, 3, { ...idle, throttle: 1 }); advance(sim, 8, { ...idle, brake: true });
    assert.ok(sim.stats().groups[group] >= minimum, `group ${group} should collapse after impact`);
    sim.rebuild(); advance(sim, 3);
    assert.equal(sim.stats().displaced, 0, 'rebuild restores the new structures');
  }
});

test('a domino collision continues to propagate after the driver brakes', () => {
  const sim = createSimulation();
  sim.chassis.position.set(-30, 1.1, 27); sim.chassis.aabbNeedsUpdate = true;
  advance(sim, 2); advance(sim, 1.2, { ...idle, throttle: 1 });
  const initially = sim.stats().groups[4];
  advance(sim, 20, { ...idle, brake: true });
  assert.ok(sim.stats().groups[4] >= initially + 4, 'falling panels should knock on into their neighbors');
  assert.ok(sim.chassis.position.z > 16, 'the car stops near the beginning of the run');
});