class List {
  constructor () {
    this.dataSouce = []
  }

  add (index, element) {
    if (element.indexOf(',') > 0) {
      const arr = element.split(',')
      for (const k in arr) {
        if (!this.contains(element)) {
          this._addElement(index, arr[k])
        }
      }
    } else if (!this.contains(element)) {
      this._addElement(index, element)
    }
  }

  _addIndex (index, element) {
    const newArr = []
    for (var i = this.dataSouce.length - 1; i > index - 1; i--) {
      newArr[i + 1] = this.dataSouce[i]
    }
    newArr[index] = element
    this.dataSouce = newArr
  }

  _addElement (index, element) {
    if (!index) {
      this.addEnd(element)
    } else if (index >= this.dataSouce.length) {
      this.addEnd(element)
    } else if (index === 1) {
      this.addFront(element)
    } else {
      this._addIndex(index, element)
    }
  }

  /**
    * 在列表的末尾添加新元素
    * @param {*} element 要添加的元素
    */
  addEnd (element) {
    if (!this.contains(element)) {
      this.dataSouce[this.dataSouce.length] = element
    }
  }

  /**
    * 在列表头部添加新元素
    * @param {*} element
    * @param {*} after
    */
  addFront (element) {
    if (!this.contains(element)) {
      this._addIndex(0, element)
    }
  }

  /**
     * 在列表中移除一个元素
     * @param {*} element 要删除的元素
     */
  remove (element) {
    // 查找当前元素的索引
    const index = this.dataSouce.indexOf(element)
    if (index >= 0) {
      this.dataSouce.splice(index, 1)
      return true
    }
    return false
  }

  /**
     * 判断给定的值是否在列表中
     */
  contains (element) {
    return this.dataSouce.indexOf(element) > -1
  }

  /**
     * 清楚列表中的元素
     */
  clear () {
    delete this.dataSouce
    this.dataSouce = []
  }

  /**
     * 列表的长度
     */
  length () {
    return this.dataSouce.length
  }

  join (comma) {
    this.removeBlank()
    return this.dataSouce.join(comma)
  }

  removeBlank () {
    const arr = this.dataSouce
    for (const k in arr) {
      if (!arr[k]) {
        this.dataSouce.splice(k, 1)
      }
    }
  }
}

export default List