function createElement(type, props, ...children) {
  return {
    type,
    props: {
      ...props,
      children: children.map((child) =>
        typeof child === 'object' ? child : createTextElement(child)
      )
    }
  }
}

function createTextElement(text) {
  return {
    type: 'TEXT_ELEMENT',
    props: {
      nodeValue: text,
      children: []
    }
  }
}

function createDom(fiber) {
  const dom =
    fiber.type == 'TEXT_ELEMENT'
      ? document.createTextNode('')
      : document.createElement(fiber.type)

  updateDom(dom, {}, fiber.props)

  return dom
}

const isEvent = (key) => key.startsWith('on')
const isProperty = (key) => key !== 'children' && !isEvent(key)
const isNew = (prev, next) => (key) => prev[key] !== next[key]
const isGone = (prev, next) => (key) => !(key in next)

function updateDom(dom, prevProps, nextProps) {
  //Remove old or changed event listeners
  Object.keys(prevProps)
    .filter(isEvent)
    .filter((key) => !(key in nextProps) || isNew(prevProps, nextProps)(key))
    .forEach((name) => {
      const eventType = name.toLowerCase().substring(2)
      dom.removeEventListener(eventType, prevProps[name])
    })

  // Remove old properties
  Object.keys(prevProps)
    .filter(isProperty)
    .filter(isGone(prevProps, nextProps))
    .forEach((name) => {
      dom[name] = ''
    })

  // Set new or changed properties
  Object.keys(nextProps)
    .filter(isProperty)
    .filter(isNew(prevProps, nextProps))
    .forEach((name) => {
      dom[name] = nextProps[name]
    })

  // Add event listeners
  Object.keys(nextProps)
    .filter(isEvent)
    .filter(isNew(prevProps, nextProps))
    .forEach((name) => {
      const eventType = name.toLowerCase().substring(2)
      dom.addEventListener(eventType, nextProps[name])
    })
}

function commitRoot() {
  deletions.forEach(commitWork)
  commitWork(wipRoot.child)
  currentRoot = wipRoot
  wipRoot = null
}

function commitWork(fiber) {
  if (!fiber) {
    return
  }

  let domParentFiber = fiber.parent
  while (!domParentFiber.dom) {
    domParentFiber = domParentFiber.parent
  }
  const domParent = domParentFiber.dom

  if (fiber.effectTag === 'PLACEMENT' && fiber.dom != null) {
    domParent.appendChild(fiber.dom)
  } else if (fiber.effectTag === 'UPDATE' && fiber.dom != null) {
    updateDom(fiber.dom, fiber.alternate.props, fiber.props)
  } else if (fiber.effectTag === 'DELETION') {
    commitDeletion(fiber, domParent)
  }

  commitWork(fiber.child)
  commitWork(fiber.sibling)
}

function commitDeletion(fiber, domParent) {
  if (fiber.dom) {
    domParent.removeChild(fiber.dom)
  } else {
    commitDeletion(fiber.child, domParent)
  }
}

function render(element, container) {
  wipRoot = {
    dom: container,
    props: {
      children: [element]
    },
    alternate: currentRoot
  }
  deletions = []
  nextUnitOfWork = wipRoot
}

let nextUnitOfWork = null
let currentRoot = null
let wipRoot = null
let deletions = null

function workLoop(deadline) {
  let shouldYield = false
  while (nextUnitOfWork && !shouldYield) {
    nextUnitOfWork = performUnitOfWork(nextUnitOfWork)
    shouldYield = deadline.timeRemaining() < 1
  }

  if (!nextUnitOfWork && wipRoot) {
    commitRoot()
  }

  requestIdleCallback(workLoop)
}

requestIdleCallback(workLoop)

function performUnitOfWork(fiber) {
  const isFunctionComponent = fiber.type instanceof Function
  if (isFunctionComponent) {
    updateFunctionComponent(fiber)
  } else {
    updateHostComponent(fiber)
  }

  const elements = fiber.props.children

  // fiber 和 element diff 生成新fiber
  reconcileChildren(fiber, elements)

  if (fiber.child) {
    return fiber.child
  }
  let nextFiber = fiber
  while (nextFiber) {
    if (nextFiber.sibling) {
      return nextFiber.sibling
    }
    nextFiber = nextFiber.parent
  }
}

function updateFunctionComponent(fiber) {
  const children = [fiber.type(fiber.props)]
  reconcileChildren(fiber, children)
}

function updateHostComponent(fiber) {
  if (!fiber.dom) {
    fiber.dom = createDom(fiber)
  }
  reconcileChildren(fiber, fiber.props.children)
}

function reconcileChildren(wipFiber, elements) {
  let index = 0
  let oldFiber = wipFiber.alternate && wipFiber.alternate.child
  let prevSibling = null

  while (index < elements.length || oldFiber != null) {
    const element = elements[index]
    let newFiber = null

    const sameType = oldFiber && element && element.type == oldFiber.type

    if (sameType) {
      newFiber = {
        type: oldFiber.type,
        props: element.props,
        dom: oldFiber.dom,
        parent: wipFiber,
        alternate: oldFiber,
        effectTag: 'UPDATE'
      }
    }
    if (element && !sameType) {
      newFiber = {
        type: element.type,
        props: element.props,
        dom: null,
        parent: wipFiber,
        alternate: null,
        effectTag: 'PLACEMENT'
      }
    }
    if (oldFiber && !sameType) {
      oldFiber.effectTag = 'DELETION'
      deletions.push(oldFiber)
    }

    if (oldFiber) {
      oldFiber = oldFiber.sibling
    }

    if (index === 0) {
      wipFiber.child = newFiber
    } else if (element) {
      prevSibling.sibling = newFiber
    }

    prevSibling = newFiber
    index++
  }
}

const MyReact = {
  createElement,
  render
}

/** @jsx MyReact.createElement */
function App(props) {
  return <h1>Hi {props.name}</h1>
}
const element = <App name="foo" />
const container = document.getElementById('root')
MyReact.render(element, container)

function createElement(type, props, ...children) {
  return {
    type,
    props: {
      ...props,
      children: children.map((child) =>
        typeof child === 'object' ? child : createTextElement(child)
      )
    }
  }
}

function createTextElement(text) {
  return {
    type: 'TEXT_ELEMENT',
    props: {
      nodeValue: text,
      children: []
    }
  }
}

function createDom(fiber) {
  const dom =
    fiber.type == 'TEXT_ELEMENT'
      ? document.createTextNode('')
      : document.createElement(fiber.type)

  updateDom(dom, {}, fiber.props)

  return dom
}

const isEvent = (key) => key.startsWith('on')
const isProperty = (key) => key !== 'children' && !isEvent(key)
const isNew = (prev, next) => (key) => prev[key] !== next[key]
const isGone = (prev, next) => (key) => !(key in next)

function updateDom(dom, prevProps, nextProps) {
  //Remove old or changed event listeners
  Object.keys(prevProps)
    .filter(isEvent)
    .filter((key) => !(key in nextProps) || isNew(prevProps, nextProps)(key))
    .forEach((name) => {
      const eventType = name.toLowerCase().substring(2)
      dom.removeEventListener(eventType, prevProps[name])
    })

  // Remove old properties
  Object.keys(prevProps)
    .filter(isProperty)
    .filter(isGone(prevProps, nextProps))
    .forEach((name) => {
      dom[name] = ''
    })

  // Set new or changed properties
  Object.keys(nextProps)
    .filter(isProperty)
    .filter(isNew(prevProps, nextProps))
    .forEach((name) => {
      dom[name] = nextProps[name]
    })

  // Add event listeners
  Object.keys(nextProps)
    .filter(isEvent)
    .filter(isNew(prevProps, nextProps))
    .forEach((name) => {
      const eventType = name.toLowerCase().substring(2)
      dom.addEventListener(eventType, nextProps[name])
    })
}

function commitRoot() {
  deletions.forEach(commitWork)
  commitWork(wipRoot.child)
  currentRoot = wipRoot
  wipRoot = null
}

function commitWork(fiber) {
  if (!fiber) {
    return
  }

  let domParentFiber = fiber.parent
  while (!domParentFiber.dom) {
    domParentFiber = domParentFiber.parent
  }
  const domParent = domParentFiber.dom

  if (fiber.effectTag === 'PLACEMENT' && fiber.dom != null) {
    domParent.appendChild(fiber.dom)
  } else if (fiber.effectTag === 'UPDATE' && fiber.dom != null) {
    updateDom(fiber.dom, fiber.alternate.props, fiber.props)
  } else if (fiber.effectTag === 'DELETION') {
    commitDeletion(fiber, domParent)
  }

  commitWork(fiber.child)
  commitWork(fiber.sibling)
}

function commitDeletion(fiber, domParent) {
  if (fiber.dom) {
    domParent.removeChild(fiber.dom)
  } else {
    commitDeletion(fiber.child, domParent)
  }
}

function render(element, container) {
  wipRoot = {
    dom: container,
    props: {
      children: [element]
    },
    alternate: currentRoot
  }
  deletions = []
  nextUnitOfWork = wipRoot
}

let nextUnitOfWork = null
let currentRoot = null
let wipRoot = null
let deletions = null

function workLoop(deadline) {
  let shouldYield = false
  while (nextUnitOfWork && !shouldYield) {
    nextUnitOfWork = performUnitOfWork(nextUnitOfWork)
    shouldYield = deadline.timeRemaining() < 1
  }

  if (!nextUnitOfWork && wipRoot) {
    commitRoot()
  }

  requestIdleCallback(workLoop)
}

requestIdleCallback(workLoop)

function performUnitOfWork(fiber) {
  const isFunctionComponent = fiber.type instanceof Function
  if (isFunctionComponent) {
    updateFunctionComponent(fiber)
  } else {
    updateHostComponent(fiber)
  }

  const elements = fiber.props.children

  // fiber 和 element diff 生成新fiber
  reconcileChildren(fiber, elements)

  if (fiber.child) {
    return fiber.child
  }
  let nextFiber = fiber
  while (nextFiber) {
    if (nextFiber.sibling) {
      return nextFiber.sibling
    }
    nextFiber = nextFiber.parent
  }
}

function updateFunctionComponent(fiber) {
  const children = [fiber.type(fiber.props)]
  reconcileChildren(fiber, children)
}

function updateHostComponent(fiber) {
  if (!fiber.dom) {
    fiber.dom = createDom(fiber)
  }
  reconcileChildren(fiber, fiber.props.children)
}

function reconcileChildren(wipFiber, elements) {
  let index = 0
  let oldFiber = wipFiber.alternate && wipFiber.alternate.child
  let prevSibling = null

  while (index < elements.length || oldFiber != null) {
    const element = elements[index]
    let newFiber = null

    const sameType = oldFiber && element && element.type == oldFiber.type

    if (sameType) {
      newFiber = {
        type: oldFiber.type,
        props: element.props,
        dom: oldFiber.dom,
        parent: wipFiber,
        alternate: oldFiber,
        effectTag: 'UPDATE'
      }
    }
    if (element && !sameType) {
      newFiber = {
        type: element.type,
        props: element.props,
        dom: null,
        parent: wipFiber,
        alternate: null,
        effectTag: 'PLACEMENT'
      }
    }
    if (oldFiber && !sameType) {
      oldFiber.effectTag = 'DELETION'
      deletions.push(oldFiber)
    }

    if (oldFiber) {
      oldFiber = oldFiber.sibling
    }

    if (index === 0) {
      wipFiber.child = newFiber
    } else if (element) {
      prevSibling.sibling = newFiber
    }

    prevSibling = newFiber
    index++
  }
}

const MyReact = {
  createElement,
  render
}

/** @jsx MyReact.createElement */
function App(props) {
  return <h1>Hi {props.name}</h1>
}
const element = <App name="foo" />
const container = document.getElementById('root')
MyReact.render(element, container)