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

/**

 * Step and slide, on a grid written out here rather than the real map, so

 * the cases are the ones being argued about: a wall, an inner corner, and a

 * body already pressed against both.

 */

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

import { BODY_R, circleBlocked, moveSpeed, RUN, slideCircle } from "./glide.ts";

const TILE = 80;

// A room with solid walls, open from (1,1) to (3,3).

const room = ["#####", "#...#", "#...#", "#...#", "#####"];

const solid = (col: number, row: number): boolean =>

  col < 0 || row < 0 || row >= room.length || col >= room[0]!.length || room[row]![col] === "#";

const slide = (x: number, y: number, dx: number, dy: number) =>

  slideCircle(x, y, dx, dy, BODY_R, solid, TILE);

test("an unobstructed step is the step it was asked for", () => {

  const to = slide(200, 200, 12, -7);

  expect(to.x).toBeCloseTo(212, 9);

  expect(to.y).toBeCloseTo(193, 9);

  expect(slide(200, 200, 0, 0)).toEqual({ x: 200, y: 200 });

});

test("a wall keeps the motion along it: running into it still slides", () => {

  // Hard against the right-hand wall (x = 320 - 16), running down and right.

  const to = slide(300, 160, 10, 10);

  expect(to.y).toBeCloseTo(170, 6); // the free axis goes through whole

  expect(to.x).toBeLessThanOrEqual(304);

  expect(to.x).toBeGreaterThan(300); // and the blocked one creeps up to the wall

  expect(circleBlocked(to.x, to.y, BODY_R, solid, TILE)).toBe(false);

});

test("a corner is one place, whichever axis is resolved first", () => {

  // The bottom-right inner corner of the room: both walls at once.

  const diagonal = slide(280, 280, 40, 40);

  // Getting there one axis at a time, either order, lands in the same place.

  const alongX = slide(280, 280, 40, 0);

  const xThenY = slide(alongX.x, alongX.y, 0, 40);

  const alongY = slide(280, 280, 0, 40);

  const yThenX = slide(alongY.x, alongY.y, 40, 0);

  expect(xThenY.x).toBeCloseTo(diagonal.x, 3);

  expect(xThenY.y).toBeCloseTo(diagonal.y, 3);

  expect(yThenX.x).toBeCloseTo(diagonal.x, 3);

  expect(yThenX.y).toBeCloseTo(diagonal.y, 3);

  // And it is the corner: a body's radius from both walls, inside them.

  expect(diagonal.x).toBeGreaterThan(320 - BODY_R - 1.5);

  expect(diagonal.x).toBeLessThanOrEqual(320 - BODY_R);

  expect(diagonal.y).toBeGreaterThan(320 - BODY_R - 1.5);

  expect(diagonal.y).toBeLessThanOrEqual(320 - BODY_R);

});

test("a body held against a wall stops moving instead of alternating", () => {

  // This is the skip: the old resolution snapped to the tile edge on the

  // blocked tick and moved freely on the next, so a player leaning on a

  // wall produced a position that changed every tick with no input change.

  let at = { x: 300, y: 200 };

  const seen: number[] = [];

  for (let i = 0; i < 12; i++) {

    at = slide(at.x, at.y, 8.3, 0);

    seen.push(at.x);

  }

  const settled = seen.slice(4);

  expect(Math.max(...settled) - Math.min(...settled)).toBeLessThan(0.05);

  expect(Math.max(...settled)).toBeLessThanOrEqual(320 - BODY_R);

});

test("a corner is a fixed point: pressed into it, nothing moves at all", () => {

  let at = { x: 300, y: 300 };

  for (let i = 0; i < 6; i++) at = slide(at.x, at.y, 8.3, 8.3);

  const settled = slide(at.x, at.y, 8.3, 8.3);

  expect(settled.x).toBeCloseTo(at.x, 6);

  expect(settled.y).toBeCloseTo(at.y, 6);

});

test("a step never ends inside a wall, from anywhere in the room", () => {

  for (let x = 96; x < 320 - 16; x += 7)

    for (let y = 96; y < 320 - 16; y += 7)

      for (const [dx, dy] of [

        [30, 0],

        [-30, 0],

        [0, 30],

        [0, -30],

        [24, 24],

        [-24, 24],

        [24, -24],

        [-24, -24],

      ] as const) {

        const to = slide(x, y, dx, dy);

        expect(circleBlocked(to.x, to.y, BODY_R, solid, TILE)).toBe(false);

      }

});

test("speed is the one table both sides read", () => {

  expect(moveSpeed({})).toBe(RUN);

  expect(moveSpeed({ haste: true })).toBeCloseTo(RUN * 1.35, 9);

  expect(moveSpeed({ slow: true })).toBeCloseTo(RUN * 0.55, 9);

  expect(moveSpeed({ heavy: true })).toBeCloseTo(RUN * 0.86, 9);

  expect(moveSpeed({ stopped: true, haste: true })).toBe(0);

});