export function mountVNode (vnode: VNode, isSvg?: boolean, parentContext?, parentComponent?) {
  if (vnode.isSvg) {
    isSvg = true
  } else if (vnode.type === 'svg') {
    isSvg = true
  /* istanbul ignore next */
  } else if (!isSupportSVG) {
    isSvg = false
  }
  if (isSvg) {
    vnode.namespace = SVG_NAMESPACE
    vnode.isSvg = isSvg
  }
  const domNode = !isSvg
    ? doc.createElement(vnode.type)
    : doc.createElementNS(vnode.namespace, vnode.type)
  setProps(domNode, vnode, isSvg as boolean)
  if (vnode.type === 'foreignObject') {
    isSvg = false
  }
  const children = vnode.children
  if (isArray(children)) {
    for (let i = 0, len = children.length; i < len; i++) {
      mountChild(children[i] as VNode, domNode, parentContext, parentComponent, isSvg)
    }
  } else {
    mountChild(children as VNode, domNode, parentContext, parentComponent, isSvg)
  }
  vnode.dom = domNode
  if (vnode.ref !== null) {
    Ref.attach(vnode, vnode.ref, domNode)
  }
  return domNode
}

function h (type: string, props: Props, children?: VirtualChildren) {
  let childNodes
  if (props.children) {
    if (!children) {
      children = props.children
    }
    delete props.children
  }
  if (isArray(children)) {
    childNodes = []
    addChildren(childNodes, children as any, type)
  } else if (isString(children) || isNumber(children)) {
    children = createVText(String(children))
  } else if (!isValidElement(children)) {
    children = EMPTY_CHILDREN
  }
  return createVNode(
    type,
    props,
    childNodes !== undefined ? childNodes : children,
    props.key,
    props.namespace,
    props.owner,
    props.ref
  ) as VNode
}

export default function cloneElement (vnode, props?: object, ...children): any {
  if (isVText(vnode)) {
    vnode.dom = null
    return vnode
  }
  if (isString(vnode)) {
    return createVText(vnode)
  }
  const properties = clone(extend(clone(vnode.props), props))
  if (vnode.namespace) {
    properties.namespace = vnode.namespace
  }
  let childrenTmp =
    (arguments.length > 2 ?
      [].slice.call(arguments, 2) :
      vnode.children || properties.children) || []
  if (childrenTmp.length) {
    if (childrenTmp.length === 1) {
      childrenTmp = children[0]
    }
  }
  if (isArray(vnode)) {
    return vnode.map((item) => {
      return cloneElement(item)
    })
  }
  const newVNode = createElement(vnode.type, properties)
  if (isArray(childrenTmp)) {
    const _children = childrenTmp.map((child) => {
      return cloneElement(child, child.props)
    })
    if (isVNode(newVNode)) {
      newVNode.children = _children
    }
    newVNode.props.children = _children
  } else if (childrenTmp) {
    if (isVNode(newVNode)) {
      newVNode.children = childrenTmp
    }
    newVNode.props.children = cloneElement(childrenTmp, childrenTmp.props)
  }
  return newVNode
}

function flatten (arr, result) {
  for (let i = 0, len = arr.length; i < len; i++) {
    const value = arr[i]
    if (isArray(value)) {
      flatten(value, result)
    } else {
      result.push(value)
    }
  }
  return result
}

export function unmountChildren (
  children: VirtualChildren,
  parentDom?: Element
) {
  if (isArray(children)) {
    for (let i = 0, len = children.length; i < len; i++) {
      unmount(children[i], parentDom)
    }
  } else {
    unmount(children, parentDom)
  }
}

export function patchChildren (
  parentDom: Element,
  lastChildren,
  nextChildren,
  context: object,
  isSvg: boolean
) {
  if (lastChildren === nextChildren) {
    return
  }
  const lastChildrenIsArray = isArray(lastChildren)
  const nextChildrenIsArray = isArray(nextChildren)
  if (lastChildrenIsArray && nextChildrenIsArray) {
    patchArrayChildren(parentDom, lastChildren, nextChildren, context, isSvg)
  } else if (!lastChildrenIsArray && !nextChildrenIsArray) {
    patch(lastChildren, nextChildren, parentDom, context, isSvg)
  } else if (lastChildrenIsArray && !nextChildrenIsArray) {
    patchArrayChildren(parentDom, lastChildren, [nextChildren], context, isSvg)
  } else if (!lastChildrenIsArray && nextChildrenIsArray) {
    patchArrayChildren(parentDom, [lastChildren], nextChildren, context, isSvg)
  }
}

function addChildren (
  childNodes: VirtualNode[],
  children: VirtualNode | VirtualNode[],
  type: string
) {
  if (isString(children) || isNumber(children)) {
    childNodes.push(createVText(String(children)))
  } else if (isValidElement(children)) {
    childNodes.push(children)
  } else if (isArray(children)) {
    for (let i = 0; i < children.length; i++) {
      addChildren(childNodes, children[i], type)
    }
  }
}

function createElement (
  vnode: VirtualNode | VirtualNode[],
  isSvg?: boolean,
  parentContext?,
  parentComponent?
): Element | Text | Comment | DocumentFragment | null {
  let domNode
  if (isValidElement(vnode)) {
    const vtype = vnode.vtype
    if (vtype & (VType.Composite | VType.Stateless)) {
      domNode = (vnode as CompositeComponent).init(parentContext, parentComponent)
      options.afterMount(vnode as CompositeComponent)
    } else if (vtype & VType.Text) {
      domNode = doc.createTextNode((vnode as any).text);
      (vnode as any).dom = domNode
    } else if (vtype & VType.Node) {
      domNode = mountVNode(vnode as any, isSvg, parentContext, parentComponent)
    } else if (vtype & VType.Void) {
      domNode = (vnode as any).dom
    }
  } else if (isString(vnode) || isNumber(vnode)) {
    domNode = doc.createTextNode(vnode as string)
  } else if (isNullOrUndef(vnode) || (vnode as any) === false) {
    domNode = doc.createTextNode('')
  } else if (isArray(vnode)) {
    domNode = doc.createDocumentFragment()
    vnode.forEach((child) => {
      if (!isInvalid(child)) {
        const childNode = createElement(child, isSvg, parentContext, parentComponent)
        if (childNode) {
          domNode.appendChild(childNode)
        }
      }
    })
  } else {
    throw new Error('Unsupported VNode.')
  }
  return domNode
}

    return children.length
  },
  only (children: Array<VirtualChildren | any>): VirtualChildren | any {
    children = Children.toArray(children)
    if (children.length !== 1) {
      throw new Error('Children.only() expects only one child.')
    }
    return children[0]
  },
  toArray (
    children: Array<VirtualChildren | any>
  ): Array<VirtualChildren | any> {
    if (isNullOrUndef(children)) {
      return []
    }
    if (isArray(children)) {
      const result = []

      flatten(children, result)

      return result
    }
    return EMPTY_CHILDREN.concat(children)
  }
}

function flatten (arr, result) {
  for (let i = 0, len = arr.length; i < len; i++) {
    const value = arr[i]
    if (isArray(value)) {
      flatten(value, result)

function renderVNodeToString (vnode, parent, context, isSvg?: boolean) {
  if (isInvalid(vnode)) {
    return ''
  }
  const { type, props, children } = vnode
  if (isVText(vnode)) {
    return encodeEntities(vnode.text)
  } else if (isVNode(vnode)) {
    let renderedString = `<${type}`
    let html
    if (!isNullOrUndef(props)) {
      for (let prop in props) {
        const value = props[prop]
        if (skipAttributes[prop]) {
          continue
        }
        if (prop === 'dangerouslySetInnerHTML') {
          html = value.__html
        } else if (prop === 'style') {
          const styleStr = renderStylesToString(value)
          renderedString += styleStr ? ` style="${renderStylesToString(value)}"` : ''
        } else if (prop === 'class' || prop === 'className') {
          renderedString += ` class="${isString(value)
            ? value
            : hashToClassName(value)}"`
        } else if (prop === 'defaultValue') {
          if (!props.value) {
            renderedString += ` value="${encodeEntities(value)}"`
          }
        } else if (prop === 'defaultChecked') {
          if (!props.checked) {
            renderedString += ` checked="${value}"`
          }
        } else if (isSvg && prop.match(/^xlink\:?(.+)/)) {
          prop = prop.toLowerCase().replace(/^xlink\:?(.+)/, 'xlink:$1')
          renderedString += ` ${prop}="${encodeEntities(value)}"`
        } else {
          if (isString(value)) {
            renderedString += ` ${prop}="${encodeEntities(value)}"`
          } else if (isNumber(value)) {
            renderedString += ` ${prop}="${value}"`
          } else if (value === true) {
            renderedString += ` ${prop}`
          }
        }
      }
    }
    if (isVoidElements[type]) {
      renderedString += `/>`
    } else {
      renderedString += `>`
      if (html) {
        renderedString += html
      } else if (!isInvalid(children)) {
        if (isString(children)) {
          renderedString += children === '' ? ' ' : encodeEntities(children)
        } else if (isNumber(children)) {
          renderedString += children + ''
        } else if (isArray(children)) {
          for (let i = 0, len = children.length; i < len; i++) {
            const child = children[i]
            if (isString(child)) {
              renderedString += child === '' ? ' ' : encodeEntities(child)
            } else if (isNumber(child)) {
              renderedString += child
            } else if (!isInvalid(child)) {
              isSvg = type === 'svg' ? true : type === 'foreignObject' ? false : isSvg
              renderedString += renderVNodeToString(
                child,
                vnode,
                context,
                isSvg
              )
            }
          }
        } else {
          isSvg = type === 'svg' ? true : type === 'foreignObject' ? false : isSvg
          renderedString += renderVNodeToString(children, vnode, context, isSvg)
        }
      }
      if (!isVoidElements[type]) {
        renderedString += `</${type}>`
      }
    }
    return renderedString
  } else if (isComposite(vnode)) {
    const instance = new type(props, context)
    instance._disable = true
    instance.props = props
    instance.context = context
    if (isFunction(instance.componentWillMount)) {
      instance.componentWillMount()
    }
    const rendered = instance.render()
    if (isFunction(instance.getChildContext)) {
      context = extend(clone(context), instance.getChildContext())
    }
    return renderVNodeToString(rendered, vnode, context, isSvg)
  } else if (isStateless(vnode)) {
    const rendered = type(props, context)
//.........这里部分代码省略.........