import { afterEach, expect, test } from "bun:test";
import { holdDecision, reducedMotion, viewTransition } from "../src/motion";

const g = globalThis as Record<string, unknown>;
afterEach(() => { delete g.document; delete g.window; });

function env({ reduce = false, vt = true, hidden = false } = {}) {
  const calls: string[] = [];
  g.window = { matchMedia: (q: string) => ({ matches: q.includes("prefers-reduced-motion: reduce") && reduce }) };
  g.document = {
    visibilityState: hidden ? "hidden" : "visible",
    ...(vt ? { startViewTransition: (cb: () => void) => { calls.push("vt"); cb(); return { finished: Promise.resolve() }; } } : {}),
  };
  return calls;
}

test("reducedMotion follows the media query and is false without a window", () => {
  expect(reducedMotion()).toBe(false);
  env({ reduce: true });
  expect(reducedMotion()).toBe(true);
  env({ reduce: false });
  expect(reducedMotion()).toBe(false);
});

test("viewTransition runs the update inside startViewTransition when it can", () => {
  const calls = env();
  viewTransition(() => calls.push("update"));
  expect(calls).toEqual(["vt", "update"]);
});

test("viewTransition runs the update directly with reduced motion, without support, or in a hidden tab", () => {
  for (const o of [{ reduce: true }, { vt: false }, { hidden: true }]) {
    const calls = env(o);
    viewTransition(() => calls.push("update"));
    expect([o, calls]).toEqual([o, ["update"]]);
  }
  delete g.document; delete g.window;
  const plain: string[] = [];
  viewTransition(() => plain.push("update"));
  expect(plain).toEqual(["update"]);
});

test("holdDecision: show the first value, hold while loading, swap to a new key, replace the same key", () => {
  type L = { id: string; course: string };
  const key = (l: L) => l.id;
  const sameCourse = (c: string) => (l: L) => l.course === c;
  const a = { id: "a", course: "x" }, b = { id: "b", course: "x" }, a2 = { id: "a", course: "x" };
  expect(holdDecision<L>(null, null, key)).toBe("show-next");
  expect(holdDecision<L>(null, a, key)).toBe("show-next");
  expect(holdDecision<L>(a, a, key)).toBe("show-next");
  expect(holdDecision<L>(a, null, key, sameCourse("x"))).toBe("hold");
  expect(holdDecision<L>(a, null, key, sameCourse("y"))).toBe("replace");
  expect(holdDecision<L>(a, b, key)).toBe("swap");
  expect(holdDecision<L>(a, a2, key)).toBe("replace");
  expect(holdDecision<L>(a, b, key, sameCourse("y"))).toBe("replace");
});