import { expect, test } from "bun:test";
import { makeGrid } from "./grid.ts";

const LINES = ["#########", "#.......#", "#.##.##.#", "#.......#", "#########"];
const cells = (g: ReturnType<typeof makeGrid>) => g.cellsOf(".");

test("many distances to one fixed target build one field", () => {
  const g = makeGrid(LINES, 10);
  const target = cells(g)[0]!;
  for (const from of cells(g)) g.walkDistance(from, target);
  expect(g.fieldsBuilt()).toBe(1);
});

test("varying the target builds a field per target", () => {
  const g = makeGrid(LINES, 10);
  const from = cells(g)[0]!;
  for (const to of cells(g)) g.walkDistance(from, to);
  expect(g.fieldsBuilt()).toBe(cells(g).length);
});

test("pathStep shares the field walkDistance built for the goal", () => {
  const g = makeGrid(LINES, 10);
  const goal = cells(g).at(-1)!;
  for (const from of cells(g)) {
    g.walkDistance(from, goal);
    g.pathStep(from, goal);
  }
  expect(g.fieldsBuilt()).toBe(1);
});

test("walk distance is symmetric, so swapping the arguments is safe", () => {
  const g = makeGrid(LINES, 10);
  for (const a of cells(g)) for (const b of cells(g)) expect(g.walkDistance(a, b)).toBe(g.walkDistance(b, a));
});

test("clearPaths forgets the fields, so the next ask builds again", () => {
  const g = makeGrid(LINES, 10);
  const [a, b] = cells(g);
  g.walkDistance(a!, b!);
  g.clearPaths();
  g.walkDistance(a!, b!);
  expect(g.fieldsBuilt()).toBe(2);
});