benjivers/val Public Public: anyone can read this; the crew can change it.

/**

 * How a bot points a gun, tested as the pure maths it is. That the gate is

 * actually wired to a trigger is the game's to prove: `src/aim.test.ts`.

 */

import { expect, test } from "bun:test";

import {

  acquire,

  aimCone,

  canFire,

  CONE_FLOOR,

  crossRate,

  drift,

  emptyTrack,

  FORGET,

  heldFor,

  lose,

  REACTION_MAX,

  REACTION_MIN,

  reactionTime,

} from "./aim.ts";

const rolls = (...values: number[]) => {

  let at = 0;

  return () => values[at++ % values.length]!;

};

test("the reaction a bot draws is between 200 and 350ms, whatever the roll", () => {

  expect(reactionTime(0)).toBeCloseTo(REACTION_MIN, 9);

  expect(reactionTime(1)).toBeCloseTo(REACTION_MAX, 9);

  expect(reactionTime(0.5)).toBeCloseTo((REACTION_MIN + REACTION_MAX) / 2, 9);

  // A roll out of range is still a reaction, not a bot that never shoots.

  expect(reactionTime(-3)).toBe(REACTION_MIN);

  expect(reactionTime(9)).toBe(REACTION_MAX);

});

test("the trigger gate is a pure function of when acquisition happened", () => {

  const track = emptyTrack();

  // Nothing in sight is never a shot, however long the round has run.

  expect(canFire(track, 100)).toBe(false);

  acquire(track, "bot-red-1", 10, { x: 0, y: 0 }, rolls(0, 0.5));

  expect(track.reaction).toBeCloseTo(REACTION_MIN, 9);

  expect(canFire(track, 10)).toBe(false);

  expect(canFire(track, 10.19)).toBe(false);

  expect(canFire(track, 10.21)).toBe(true);

  expect(canFire(track, 12)).toBe(true);

  expect(heldFor(track, 12)).toBeCloseTo(2, 9);

});

test("a new target starts the reaction again; the same one does not", () => {

  const track = emptyTrack();

  acquire(track, "one", 5, { x: 100, y: 100 }, rolls(1, 0.5));

  expect(track.since).toBe(5);

  acquire(track, "one", 5.3, { x: 180, y: 100 }, rolls(0, 0.5));

  expect(track.since).toBe(5); // the hold carries on

  expect(canFire(track, 5.4)).toBe(true);

  acquire(track, "two", 5.4, { x: 0, y: 0 }, rolls(0, 0.5));

  expect(track.since).toBe(5.4); // swinging onto somebody else costs again

  expect(canFire(track, 5.5)).toBe(false);

});

test("a hold survives a blink out of sight, and no longer", () => {

  const track = emptyTrack();

  acquire(track, "one", 1, { x: 0, y: 0 }, rolls(0, 0.5));

  lose(track, 1 + FORGET / 2);

  expect(track.id).toBe("one");

  // Back a moment later: the same hold, already through its reaction.

  acquire(track, "one", 1 + FORGET / 2, { x: 0, y: 0 }, rolls(0, 0.5));

  expect(track.since).toBe(1);

  // Gone for longer than that and it is a fresh acquisition.

  lose(track, 3);

  expect(track.id).toBe(null);

  acquire(track, "one", 3, { x: 0, y: 0 }, rolls(0, 0.5));

  expect(track.since).toBe(3);

  expect(canFire(track, 3.1)).toBe(false);

});

test("the cone starts wide, settles the longer one target is held, and never closes", () => {

  const swing = aimCone(0, 0);

  const second = aimCone(1, 0);

  const settled = aimCone(3, 0);

  expect(swing).toBeGreaterThan(0.08); // several degrees on the swing

  expect(second).toBeLessThan(swing / 2);

  expect(settled).toBeLessThan(second);

  expect(settled).toBeGreaterThanOrEqual(CONE_FLOOR);

  expect(aimCone(99, 0)).toBeCloseTo(CONE_FLOOR, 6);

});

test("a target crossing the view costs the bot accuracy", () => {

  expect(aimCone(3, 1)).toBeGreaterThan(aimCone(3, 0) * 3);

  expect(aimCone(3, 0.5)).toBeGreaterThan(aimCone(3, 0));

  expect(aimCone(3, 0.5)).toBeLessThan(aimCone(3, 1));

  // Nonsense from the caller is clamped, not multiplied out.

  expect(aimCone(3, 50)).toBeCloseTo(aimCone(3, 1), 9);

});

test("crossing is measured across the sight line, not along it", () => {

  const bot = { x: 0, y: 0 };

  const walking = emptyTrack();

  acquire(walking, "t", 0, { x: 300, y: 0 }, rolls(0, 0.5));

  // Straight down the barrel: nothing to track.

  expect(crossRate(walking, bot, { x: 260, y: 0 }, 0.1)).toBeCloseTo(0, 6);

  const strafing = emptyTrack();

  acquire(strafing, "t", 0, { x: 300, y: 0 }, rolls(0, 0.5));

  // Straight across it at a run: all of it but the turn of the sight line.

  expect(crossRate(strafing, bot, { x: 300, y: 25 }, 0.1)).toBeCloseTo(250, -1);

  // And it remembers where the target went, so the next tick measures again.

  expect(crossRate(strafing, bot, { x: 300, y: 25 }, 0.1)).toBeCloseTo(0, 6);

});

test("the error wanders inside the cone instead of being redrawn every tick", () => {

  const track = emptyTrack();

  acquire(track, "one", 0, { x: 0, y: 0 }, rolls(0, 1));

  // Drawn at the edge of the swing cone on acquisition.

  expect(Math.abs(track.error)).toBeCloseTo(aimCone(0, 0), 9);

  // One tick moves it a little, not to somewhere unrelated.

  const before = track.error;

  const after = drift(track, aimCone(0, 0), 1 / 30, rolls(0.9));

  expect(Math.abs(after - before)).toBeLessThan(aimCone(0, 0) / 4);

  // And it is squeezed toward the barrel as the cone closes around it.

  for (let i = 0; i < 90; i++) drift(track, aimCone(3, 0), 1 / 30, rolls(0.5, 1, 0));

  expect(Math.abs(track.error)).toBeLessThanOrEqual(aimCone(3, 0) + 1e-12);

});