/* DCTS 轮询器单测（node:test，零依赖）
 *
 * utils/polling.js 的 createPoller：指数退避、failCount 重置/增长、stop 清理。
 * 通过 stubbing setTimeout / clearTimeout 捕获调度延迟，不真等 5s+。
 *
 * 时序说明：start() 触发 schedule() 时 fn 是同步调用的（calls 立即生效），
 * 后续的 failCount 更新与 setTimeout 排期发生在微任务里——`await p.start()`
 * 之后测试续体排在其后，故断言时调度已完成（确定性）。
 */

import { test } from 'node:test';
import assert from 'node:assert/strict';
import { createPoller } from '../src/utils/polling.js';

// 最小 document stub：node 环境无 DOM，轮询器只在 visibilitychange 处触碰 document。
function installDocStub() {
  const doc = { hidden: false, addEventListener() {}, removeEventListener() {} };
  const prev = globalThis.document;
  globalThis.document = doc;
  return { doc, restore() { globalThis.document = prev; } };
}

// 捕获 setTimeout 调用。fire(n) 手动执行第 n 次已排定的回调（await 其完整完成）。
function captureTimers() {
  const realSet = globalThis.setTimeout;
  const realClear = globalThis.clearTimeout;
  const scheduled = [];
  globalThis.setTimeout = (fn, ms) => {
    const id = { fn, ms };
    scheduled.push(id);
    return id;
  };
  globalThis.clearTimeout = (id) => {
    const i = scheduled.indexOf(id);
    if (i >= 0) scheduled.splice(i, 1);
  };
  return {
    delays: () => scheduled.map(t => t.ms),
    fire: async (n) => { await scheduled[n].fn(); },
    restore() {
      globalThis.setTimeout = realSet;
      globalThis.clearTimeout = realClear;
    },
  };
}

test('start() 立即执行一次 fn', async () => {
  const stub = installDocStub();
  const timers = captureTimers();
  let calls = 0;
  const p = createPoller(() => { calls++; return true; }, { baseMs: 5000 });
  await p.start();
  assert.equal(calls, 1); // 立即跑了一次（fn 同步调用）
  assert.equal(p.isRunning(), true);
  // 成功后下一轮间隔为 baseMs
  assert.deepEqual(timers.delays(), [5000]);
  p.stop();
  timers.restore();
  stub.restore();
});

test('fn 返回 false 触发指数退避，成功后重置', async () => {
  const stub = installDocStub();
  const timers = captureTimers();
  let ok = false;
  const p = createPoller(() => ok, { baseMs: 5000, maxMs: 60000 });
  await p.start();
  // 第一次失败 → failCount=1 → 5k*2^1
  assert.deepEqual(timers.delays(), [10000]);
  await timers.fire(0); // 第二轮仍失败 → failCount=2
  assert.deepEqual(timers.delays().slice(-1), [20000]);
  ok = true;
  await timers.fire(0); // 第三轮成功 → failCount 重置
  assert.deepEqual(timers.delays().slice(-1), [5000]);
  p.stop();
  timers.restore();
  stub.restore();
});

test('fn 抛错同样计为失败', async () => {
  const stub = installDocStub();
  const timers = captureTimers();
  const p = createPoller(() => { throw new Error('boom'); }, { baseMs: 5000 });
  await p.start();
  assert.deepEqual(timers.delays().slice(-1), [10000]);
  p.stop();
  timers.restore();
  stub.restore();
});

test('stop() 清除挂起定时器且不再调度', async () => {
  const stub = installDocStub();
  const timers = captureTimers();
  let calls = 0;
  const p = createPoller(() => { calls++; return true; }, { baseMs: 5000 });
  await p.start();           // calls=1，已排下一轮
  assert.equal(timers.delays().length, 1);
  p.stop();
  assert.equal(timers.delays().length, 0); // 挂起定时器已被清除
  assert.equal(calls, 1);    // fn 未再被调用
  assert.equal(p.isRunning(), false);
  timers.restore();
  stub.restore();
});

test('triggerNow() 立即触发一次并续排', async () => {
  const stub = installDocStub();
  const timers = captureTimers();
  let calls = 0;
  const p = createPoller(() => { calls++; return true; }, { baseMs: 5000 });
  await p.start();               // calls=1
  await p.triggerNow();          // calls=2
  assert.equal(calls, 2);
  assert.equal(p.isRunning(), true);
  p.stop();
  timers.restore();
  stub.restore();
});

test('退避上限 maxMs 生效（长时间连续失败不无限增长）', async () => {
  const stub = installDocStub();
  const timers = captureTimers();
  const p = createPoller(() => false, { baseMs: 5000, maxMs: 60000, maxFails: 4 });
  await p.start();
  let maxDelay = 0;
  for (let i = 0; i < 10; i++) {
    maxDelay = Math.max(maxDelay, timers.delays()[timers.delays().length - 1] || 0);
    await timers.fire(0);
  }
  assert.ok(maxDelay <= 60000, `maxDelay=${maxDelay} 不应超过 60s`);
  assert.equal(maxDelay, 60000); // 5k*2^4 clamp 到 60s
  p.stop();
  timers.restore();
  stub.restore();
});