import Vue from 'vue'
import * as rules from './rules'
import promisify from 'util/promisify'

export default (context, options = {}) => {
 // options = { scope: 'validator', prefix: '/', ...options }

 // 只注册回调，不注册数据
 return () => {
 Vue.mixin({
  beforeCreate () {
  const options = this.$options
  const { validator } = options

  if (validator) {
   // 在入口处定义 $validation
   Vue.util.defineReactive(this, '$validation', {
   fields: [],
   errors: []
   })
   this.$validator = this
   nextTick(this, validator.auto)
  } else {
   const { parent } = options
   if (parent && parent.$validation) {
   this.$validation = parent.$validation
   this.$validator = parent.$validator
   nextTick(this, parent.$validator.$options.validator.auto)
   }
  }
  }
 })

 /**
  * $validate
  *
  * validate vm recursively.
  *
  * @return {Promise}
  */
 Vue.prototype.$validate = function (fromEntry) {
  const { validate, $validation = {}, $validator } = this

  // 如果此处为校验入口
  if ($validator === this && !fromEntry) {
  // 顶级往下校验所有子组件
  return Promise.all($validation.fields
   .map(field => field.$validate(true)))
   .then(() => $validation)
   .catch(() => Promise.reject($validation))
  } else {
  if (!validate) {
   return Promise.resolve($validation)
  }
  return Promise.all(Object.keys(validate).map(key => {
   return new Promise((resolve, reject) => {
   const { validator = rules[key], rule, message } = validate[key]
   if (validator) {
    // reject if falsy
    promisify(validator(this.value, rule), true)
    .then(resolve)
    .catch(() => {
     reject({
     field: this.field || this,
     rule,
     message
     })
    })
   } else {
    __PROD__ || console.warn(`'${key}' is NOT a valid validator`)
    resolve()
   }
   })
  })).then(() => {
   updateErrors($validation.errors, this)
   return $validation
  }).catch(error => {
   updateErrors($validation.errors, this, error)
   return Promise.reject($validation)
  })
  }
 }

 function updateErrors (errors, vm, replacement) {
  const field = vm.field || vm
  const found = errors.some((error, index) => {
  if (error.field === field) {
   if (replacement) {
   errors.splice(index, 1, replacement)
   } else {
   errors.splice(index, 1)
   }
   return true
  }
  return false
  })

  if (!found && replacement) {
  errors.push(replacement)
  }

  return errors
 }

 function nextTick (vm, auto) {
  vm.$nextTick(() => {
  // 定义了校验规则
  if (vm.validate) {
   vm.$validation.fields.push(vm)
   // 加载完成自动检查
   if (auto) {
   vm.$validate()
   }
  }
  })
 }
 }
}