const { test } = require('node:test');
const assert = require('node:assert/strict');
const { setIntervalWhenVisible } = require('./visible-timer');

class FakeDocument {
  hidden = false;
  listeners = new Set();
  addEventListener(type, listener) { if (type === 'visibilitychange') this.listeners.add(listener); }
  removeEventListener(type, listener) { if (type === 'visibilitychange') this.listeners.delete(listener); }
  setHidden(hidden) {
    this.hidden = hidden;
    for (const listener of [...this.listeners]) listener();
  }
}

function fakeClock(t, hidden = false) {
  const doc = new FakeDocument();
  doc.hidden = hidden;
  const original = {
    document: globalThis.document,
    setInterval: globalThis.setInterval,
    clearInterval: globalThis.clearInterval,
  };
  let nextId = 1;
  const timers = new Map();
  globalThis.document = doc;
  globalThis.setInterval = (fn, ms) => {
    const id = nextId++;
    timers.set(id, { fn, ms });
    return id;
  };
  globalThis.clearInterval = (id) => timers.delete(id);
  t.after(() => {
    globalThis.document = original.document;
    globalThis.setInterval = original.setInterval;
    globalThis.clearInterval = original.clearInterval;
  });
  return {
    doc,
    timers,
    tick() { for (const timer of [...timers.values()]) timer.fn(); },
  };
}

test('runs on a visible page and has one interval until hidden', (t) => {
  const clock = fakeClock(t);
  let calls = 0;
  const handle = setIntervalWhenVisible(() => calls++, 250);
  assert.equal(calls, 0);
  assert.equal(clock.timers.size, 1);
  assert.equal([...clock.timers.values()][0].ms, 250);
  clock.tick();
  assert.equal(calls, 1);
  clock.doc.setHidden(true);
  assert.equal(clock.timers.size, 0);
  clock.tick();
  assert.equal(calls, 1);
  handle.clear();
  assert.equal(clock.doc.listeners.size, 0);
});

test('immediate mode runs once initially and once when becoming visible', (t) => {
  const clock = fakeClock(t);
  let calls = 0;
  const handle = setIntervalWhenVisible(() => calls++, 1000, { immediate: true });
  assert.equal(calls, 1);
  assert.equal(clock.timers.size, 1);
  clock.doc.setHidden(true);
  assert.equal(clock.timers.size, 0);
  clock.doc.setHidden(false);
  assert.equal(calls, 2);
  assert.equal(clock.timers.size, 1);
  handle.clear();
  clock.doc.setHidden(true);
  clock.doc.setHidden(false);
  assert.equal(calls, 2);
  assert.equal(clock.timers.size, 0);
});

test('a page that starts hidden waits until visible before calling or scheduling', (t) => {
  const clock = fakeClock(t, true);
  let calls = 0;
  const handle = setIntervalWhenVisible(() => calls++, 500, { immediate: true });
  assert.equal(calls, 0);
  assert.equal(clock.timers.size, 0);
  clock.doc.setHidden(false);
  assert.equal(calls, 1);
  assert.equal(clock.timers.size, 1);
  handle.clear();
});