import { BaseLifeCycle } from 'lifeCycle';

export interface LoadMoreOption extends BaseLifeCycle{
  perPage?:number
  remote?
  beforeUpdate?
}

// == 设置列表分页
export const setPagination = (data:Array<any>, perPage?:number) => {
  perPage = perPage || 10;

  return {
    // 分页个数
    perPage: perPage,
    // 返回所有列表数据
    all: () => {
      return data;
    },
    // 返回列表数量
    count: () => {
      return data.length;
    },
    // 返回分页数据
    getPage: (startNum, endNum) => {
      return data.slice(perPage * startNum, perPage * endNum);
    },
    getByIndex: (index) => {
      return data[index];
    },
    remove: (list) => {
      data.splice(data.indexOf(list), 1);
      return data;
    },
    removeByIndex: (index) => {
      data.splice(index, 1);
      return data;
    },
    add: (list) => {
      data = data.concat(list);
      return data;
    }
  }
}


/**
 * 加载数据+下拉加载(新)
 * @param data     待加载的来源数据，可以是封装过的，也可以是未封装过的
 * @param option   相关配置
 */
export const createLoader =  (data, option:LoadMoreOption = {}) => {
  if(!data || !data.getPage)
    data = setPagination(data, option.perPage);
  const getRemoteData = option.remote;   // 远程数据接口
  const created = option.created;        // 初始化回调
  const beforeUpdate = option.beforeUpdate;// 更新前回调
  const updated = option.updated;        // 更新回调
  const destroyed = option.destroyed;    // 销毁回调
  let pageData = data.getPage(0,1);
  let current = pageData.length / data.perPage;
  let max = data.count() / data.perPage;
  let timer;
  let canBeLoaded = max > current;

  // loader触发器
  const trigger = () => {
    if(beforeUpdate) beforeUpdate();
    if(current == max){
      if(getRemoteData){
        getRemoteData(data).then((res) => {
          data.add(res); // 将新数据添加到data中
          max = data.count() / data.perPage; // 重新计算max
          if(max > current){
            update();
          }else{
            finishUpdate();
          }
        });
      }else{
        finishUpdate();
      }
    }else{
      // 设定加载间隔为360ms
      timer = setTimeout(() => {
        update();
      }, 360);
    }

    // 更新数据和当前页面标识
    function update() {
      pageData = data.getPage(0, current + 1);
      current = pageData.length / data.perPage;
      updated(pageData);
      return current;
    }

    function finishUpdate() {
      clearTimeout(timer);
      destroyed();
    }
  };

  // == 调用初始化方法时，输出当前分页数据、加载触发、是否可加载判断
  created(pageData, trigger, canBeLoaded);
}