import config from '../config'
import KNode, { createEmptyKNode } from './knode'
import { createComponent } from './create-component'
import { traverse } from '../observer/traverse'

import {
  warn,
  isDef,
  isUndef,
  isArray,
  isTrue,
  isObject,
  isPrimitive,
  resolveAsset,
  isFunction
} from '../util/index'

import { normalizeChildren, simpleNormalizeChildren } from './helpers/index'
import type { Component } from 'types/component'
import type { KNodeData } from 'types/knode'

const SIMPLE_NORMALIZE = 1
const ALWAYS_NORMALIZE = 2

// wrapper function for providing a more flexible interface
// without getting yelled at by flow
export function createElement(
  context: Component,
  tag: any,
  data: any,
  children: any,
  normalizationType: any,
  alwaysNormalize: boolean
): KNode | Array<KNode> {
  if (isArray(data) || isPrimitive(data)) {
    normalizationType = children
    children = data
    data = undefined
  }
  if (isTrue(alwaysNormalize)) {
    normalizationType = ALWAYS_NORMALIZE
  }
  return _createElement(context, tag, data, children, normalizationType)
}

export function _createElement(
  context: Component,
  tag?: string | Component | Function | Object,
  data?: KNodeData,
  children?: any,
  normalizationType?: number
): KNode | Array<KNode> {
  if (isDef(data) && isDef((data as any).__ob__)) {
    __DEV__ &&
      warn(
        `Avoid using observed data object as knode data: ${JSON.stringify(
          data
        )}\n` + 'Always create fresh knode data objects in each render!',
        context
      )
    return createEmptyKNode()
  }
  // object syntax in k-bind
  if (isDef(data) && isDef(data.is)) {
    tag = data.is
  }
  if (!tag) {
    // in case of component :is set to falsy value
    return createEmptyKNode()
  }
  // warn against non-primitive key
  if (__DEV__ && isDef(data) && isDef(data.key) && !isPrimitive(data.key)) {
    warn(
      'Avoid using non-primitive value as key, ' +
        'use string/number value instead.',
      context
    )
  }
  // support single function children as default scoped slot
  if (isArray(children) && isFunction(children[0])) {
    data = data || {}
    data.scopedSlots = { default: children[0] }
    children.length = 0
  }
  if (normalizationType === ALWAYS_NORMALIZE) {
    children = normalizeChildren(children)
  } else if (normalizationType === SIMPLE_NORMALIZE) {
    children = simpleNormalizeChildren(children)
  }
  let knode, ns
  if (typeof tag === 'string') {
    let Ctor
    ns = (context.$knode && context.$knode.ns) || config.getTagNamespace(tag)
    if (config.isReservedTag(tag)) {
      // platform built-in elements
      if (
        __DEV__ &&
        isDef(data) &&
        isDef(data.nativeOn) &&
        data.tag !== 'component'
      ) {
        warn(
          `The .native modifier for k-on is only valid on components but it was used on <${tag}>.`,
          context
        )
      }
      knode = new KNode(
        config.parsePlatformTagName(tag),
        data,
        children,
        undefined,
        undefined,
        context
      )
    } else if (
      (!data || !data.pre) &&
      isDef((Ctor = resolveAsset(context.$options, 'components', tag)))
    ) {
      // component
      knode = createComponent(Ctor, data, context, children, tag)
    } else {
      // unknown or unlisted namespaced elements
      // check at runtime because it may get assigned a namespace when its
      // parent normalizes children
      knode = new KNode(tag, data, children, undefined, undefined, context)
    }
  } else {
    // direct component options / constructor
    knode = createComponent(tag as any, data, context, children)
  }
  if (isArray(knode)) {
    return knode
  } else if (isDef(knode)) {
    if (isDef(ns)) applyNS(knode, ns)
    if (isDef(data)) registerDeepBindings(data)
    return knode
  } else {
    return createEmptyKNode()
  }
}

function applyNS(knode, ns, force?: boolean) {
  knode.ns = ns
  if (knode.tag === 'foreignObject') {
    // use default namespace inside foreignObject
    ns = undefined
    force = true
  }
  if (isDef(knode.children)) {
    for (let i = 0, l = knode.children.length; i < l; i++) {
      const child = knode.children[i]
      if (
        isDef(child.tag) &&
        (isUndef(child.ns) || (isTrue(force) && child.tag !== 'svg'))
      ) {
        applyNS(child, ns, force)
      }
    }
  }
}

// ref #5318
// necessary to ensure parent re-render when deep bindings like :style and
// :class are used on slot nodes
function registerDeepBindings(data) {
  if (isObject(data.style)) {
    traverse(data.style)
  }
  if (isObject(data.class)) {
    traverse(data.class)
  }
}