fable/val Public Public: anyone can read this; nobody can change it.

/**

 * The view angle belongs to the browser between snapshots, and the server

 * gets it back only when it has something to say that we did not.

 */

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

import { makeYaw, settle, shortWay, told, turn, SENT_TOLERANCE } from "../static/yaw.js";

const me = (angle: number, extra: Partial<{ id: string; alive: boolean }> = {}) => ({

  id: "p1",

  alive: true,

  angle,

  ...extra,

});

// The server rounds an angle to a tenth of a radian on the way out.

const echoed = (angle: number) => Math.round(angle * 10) / 10;

test("the first snapshot is where you are looking: there is no view of your own yet", () => {

  const yaw = makeYaw();

  expect(yaw.ready).toBe(false);

  expect(settle(yaw, me(1.4), 10)).toBeCloseTo(1.4, 6);

  expect(yaw.ready).toBe(true);

});

test("a snapshot does not drag the camera back to the angle it was told", () => {

  const yaw = makeYaw();

  settle(yaw, me(0), 10);

  // A flick: the mouse moves at frame rate, and every angle is announced.

  for (let i = 1; i <= 10; i++) {

    turn(yaw, 0.12);

    told(yaw, yaw.angle, 10 + i * 0.016);

  }

  expect(yaw.angle).toBeCloseTo(1.2, 6);

  // The snapshot is the angle the server last heard — four frames ago.

  settle(yaw, me(echoed(0.72)), 10.17);

  expect(yaw.angle).toBeCloseTo(1.2, 6);

});

test("an angle we never sent is a correction, and is taken", () => {

  const yaw = makeYaw();

  settle(yaw, me(0), 10);

  told(yaw, 0, 10);

  turn(yaw, 0.5);

  told(yaw, 0.5, 10.05);

  // The round starts and the match points everybody at the site.

  settle(yaw, me(-2.1), 10.1);

  expect(yaw.angle).toBeCloseTo(-2.1, 6);

});

test("an echo just inside the rounding is ours, one just outside is not", () => {

  const near = makeYaw();

  settle(near, me(0), 10);

  told(near, 0.5, 10);

  turn(near, 0.4);

  settle(near, me(0.5 + SENT_TOLERANCE / 2), 10.05);

  expect(near.angle).toBeCloseTo(0.4, 6);

  const far = makeYaw();

  settle(far, me(0), 10);

  told(far, 0.5, 10);

  turn(far, 0.4);

  settle(far, me(0.5 + SENT_TOLERANCE * 2), 10.05);

  expect(far.angle).toBeCloseTo(0.5 + SENT_TOLERANCE * 2, 6);

});

test("an echo from a second ago has expired: only recent angles are ours", () => {

  const yaw = makeYaw();

  settle(yaw, me(0), 10);

  told(yaw, 0.5, 10);

  turn(yaw, 0.4);

  settle(yaw, me(0.5), 12);

  expect(yaw.angle).toBeCloseTo(0.5, 6);

});

test("a client that has not spoken yet keeps what it has", () => {

  const yaw = makeYaw();

  settle(yaw, me(0), 10);

  turn(yaw, 0.8);

  // No input has been sent between the two snapshots; the server can only be

  // repeating what it already knew, so there is nothing here to take.

  settle(yaw, me(0), 10.03);

  expect(yaw.angle).toBeCloseTo(0.8, 6);

});

test("a respawn and a seat change both point you where the server points you", () => {

  const respawn = makeYaw();

  settle(respawn, me(0, { alive: false }), 10);

  told(respawn, 0, 10);

  turn(respawn, 1);

  settle(respawn, me(0, { alive: true }), 10.1);

  expect(respawn.angle).toBeCloseTo(0, 6);

  const seat = makeYaw();

  settle(seat, me(0), 10);

  told(seat, 0, 10);

  turn(seat, 1);

  settle(seat, { id: "p2", alive: true, angle: 0 }, 10.1);

  expect(seat.angle).toBeCloseTo(0, 6);

});

test("the wrap is taken the short way round", () => {

  expect(shortWay(3.0, -3.0)).toBeCloseTo(0.2831853, 6);

  expect(shortWay(-3.0, 3.0)).toBeCloseTo(-0.2831853, 6);

  // Which means an echo either side of π is still ours.

  const yaw = makeYaw();

  settle(yaw, me(0), 10);

  told(yaw, Math.PI - 0.01, 10);

  turn(yaw, 0.3);

  settle(yaw, me(-Math.PI + 0.01), 10.05);

  expect(yaw.angle).toBeCloseTo(0.3, 6);

});

test("the sent log does not grow without bound", () => {

  const yaw = makeYaw();

  for (let i = 0; i < 500; i++) told(yaw, i * 0.01, 10 + i * 0.05);

  expect(yaw.sent.length).toBeLessThan(30);

});