export enum NodeTypes {
  // 0 根节点 最顶层那个节点
  ROOT,
  // 1 元素节点 <Comp></Comp>
  ELEMENT,
  // 2 普通文本节点
  TEXT,
  // 3 注释节点
  COMMENT,
  // 4 表达式节点 :total="pageInfo.total" 中 pageInfo.total 就是表达式
  SIMPLE_EXPRESSION,
  // 5 插值表达式节点 {{ something }} 这种就是插值表达式
  INTERPOLATION,
  // 6 普通属性节点 style="xx" 这种不是v-bind的就会被当成普通属性节点处理
  ATTRIBUTE,
  // 7 指令节点 v-on :total .prop @on-change #a v-slot v-pre 还有自定义指令等
  // 可以看测试用例去找到指定的case vuejs/core/packages/compiler-core/__tests__/parse.spec.ts v-if v-show v-for v-bind 这种都是
  DIRECTIVE,
  // containers
  // 8 复合表达式 看测试用例的结果丢到 ast explorer 中无法解析成这个类型 看起来是 ast explorer 中版本太旧了
  COMPOUND_EXPRESSION,
  // 9 v-if 表达式
  IF,
  // 10 v-if 的节点下面会有 branches 属性
  IF_BRANCH,
  // 11 v-for 表达式 举个例子：<div v-for="item of []"></div>的父子关系是：root -> v-for -> div
  FOR,
  // 12 <div/>{{ foo }} bar {{ baz }}<div/> 中间的 bar 即是 TEXT_CALL 有点不明所以
  TEXT_CALL,
  // codegen
  // codegen 即根据template块生成代码的节点类型
  // 13
  VNODE_CALL,
  // 14
  JS_CALL_EXPRESSION,
  // 15
  JS_OBJECT_EXPRESSION,
  // 16
  JS_PROPERTY,
  // 17
  JS_ARRAY_EXPRESSION,
  // 18
  JS_FUNCTION_EXPRESSION,
  // 19
  JS_CONDITIONAL_EXPRESSION,
  // 20
  JS_CACHE_EXPRESSION,

  // ssr codegen
  JS_BLOCK_STATEMENT,
  JS_TEMPLATE_LITERAL,
  JS_IF_STATEMENT,
  JS_ASSIGNMENT_EXPRESSION,
  JS_SEQUENCE_EXPRESSION,
  JS_RETURN_STATEMENT,
}

// Here we have async deferring wrappers using microtasks.
// In 2.5 we used (macro) tasks (in combination with microtasks).
// However, it has subtle problems when state is changed right before repaint
// (e.g. #6813, out-in transitions).
// Also, using (macro) tasks in event handler would cause some weird behaviors
// that cannot be circumvented (e.g. #7109, #7153, #7546, #7834, #8109).
// So we now use microtasks everywhere, again.
// A major drawback of this tradeoff is that there are some scenarios
// where microtasks have too high a priority and fire in between supposedly
// sequential events (e.g. #4521, #6690, which have workarounds)
// or even between bubbling of the same event (#6566).
let timerFunc

// The nextTick behavior leverages the microtask queue, which can be accessed
// via either native Promise.then or MutationObserver.
// MutationObserver has wider support, however it is seriously bugged in
// UIWebView in iOS >= 9.3.3 when triggered in touch event handlers. It
// completely stops working after triggering a few times... so, if native
// Promise is available, we will use it:
/* istanbul ignore next, $flow-disable-line */
if (typeof Promise !== 'undefined' && isNative(Promise)) {
  const p = Promise.resolve()
  timerFunc = () => {
    p.then(flushCallbacks)
    // In problematic UIWebViews, Promise.then doesn't completely break, but
    // it can get stuck in a weird state where callbacks are pushed into the
    // microtask queue but the queue isn't being flushed, until the browser
    // needs to do some other work, e.g. handle a timer. Therefore we can
    // "force" the microtask queue to be flushed by adding an empty timer.
    if (isIOS) setTimeout(noop)
  }
  isUsingMicroTask = true
} else if (
  !isIE &&
  typeof MutationObserver !== 'undefined' &&
  (isNative(MutationObserver) ||
    // PhantomJS and iOS 7.x
    MutationObserver.toString() === '[object MutationObserverConstructor]')
) {
  // Use MutationObserver where native Promise is not available,
  // e.g. PhantomJS, iOS7, Android 4.4
  // (#6466 MutationObserver is unreliable in IE11)
  let counter = 1
  const observer = new MutationObserver(flushCallbacks)
  const textNode = document.createTextNode(String(counter))
  observer.observe(textNode, {
    characterData: true,
  })
  timerFunc = () => {
    counter = (counter + 1) % 2
    textNode.data = String(counter)
  }
  isUsingMicroTask = true
} else if (typeof setImmediate !== 'undefined' && isNative(setImmediate)) {
  // Fallback to setImmediate.
  // Technically it leverages the (macro) task queue,
  // but it is still a better choice than setTimeout.
  timerFunc = () => {
    setImmediate(flushCallbacks)
  }
} else {
  // Fallback to setTimeout.
  timerFunc = () => {
    setTimeout(flushCallbacks, 0)
  }
}