/* @flow */

import { extend, isObject } from 'shared/util'

function updateClass (oldVnode: VNodeWithData, vnode: VNodeWithData) {
  const el = vnode.elm
  const ctx = vnode.context

  const data: VNodeData = vnode.data
  const oldData: VNodeData = oldVnode.data
  if (!data.staticClass &&
    !data.class &&
    (!oldData || (!oldData.staticClass && !oldData.class))
  ) {
    return
  }

  const oldClassList = makeClassList(oldData)
  const classList = makeClassList(data)

  if (typeof el.setClassList === 'function') {
    el.setClassList(classList)
  } else {
    const style = getStyle(oldClassList, classList, ctx)
    if (typeof el.setStyles === 'function') {
      el.setStyles(style)
    } else {
      for (const key in style) {
        el.setStyle(key, style[key])
      }
    }
  }
}

function makeClassList (data: VNodeData): Array<string> {
  const classList = []
  // unlike web, weex vnode staticClass is an Array
  const staticClass: any = data.staticClass
  const dataClass = data.class
  if (staticClass) {
    classList.push.apply(classList, staticClass)
  }
  if (Array.isArray(dataClass)) {
    classList.push.apply(classList, dataClass)
  } else if (isObject(dataClass)) {
    classList.push.apply(classList, Object.keys(dataClass).filter(className => dataClass[className]))
  } else if (typeof dataClass === 'string') {
    classList.push.apply(classList, dataClass.trim().split(/\s+/))
  }
  return classList
}

function getStyle (oldClassList: Array<string>, classList: Array<string>, ctx: Component): Object {
  // style is a weex-only injected object
  // compiled from <style> tags in weex files
  const stylesheet: any = ctx.$options.style || {}
  const result = {}
  classList.forEach(name => {
    const style = stylesheet[name]
    extend(result, style)
  })
  oldClassList.forEach(name => {
    const style = stylesheet[name]
    for (const key in style) {
      if (!result.hasOwnProperty(key)) {
        result[key] = ''
      }
    }
  })
  return result
}

export default {
  create: updateClass,
  update: updateClass
}