import { onPullDownRefresh, onReachBottom } from "@dcloudio/uni-app";
import { onMounted, ref, type Ref } from "vue";
import type { ILoaderCommon, LoaderLoadType } from "./LoaderCommon";

export interface ISimplePageListLoader<T, P> extends ILoaderCommon<P> {
  list: Ref<T[]>;
  page: Ref<number>;
  total: Ref<number>;
}

/**
 * 说明：
 * * 简单页面分页列表加载器组合式代码。
 * @param pageSize 每页数量
 * @param loader 数据加载函数
 * @param showGlobalLoading 是否显示全局加载提示
 */
export function useSimplePageListLoader<T, P = any>(
  pageSize: number, 
  loader: (page: number, pageSize: number, params?: P) => Promise<{ list: T[], total: number }>,
  loadWhenMounted = true,
  showGlobalLoading = false,
)  : ISimplePageListLoader<T, P>
{
  
  const status = ref<LoaderLoadType>('loading');
  const error = ref('');
  const page = ref(0);
  const total = ref(0);
  const list = ref<T[]>([]) as Ref<T[]>;

  let lastParams: P | undefined;
  let loading = false;

  async function load(refresh: boolean = false, params?: P) {
    if (loading) 
      return;
    if (params)
      lastParams = params;
    if (refresh) {
      page.value = 0;
      list.value = []; 
    }
    page.value++;
    status.value = 'loading';
    loading = true;
    if (showGlobalLoading)
      uni.showLoading({ title: '加载中...' });

    try {
      const res = (await loader(page.value, pageSize, lastParams));
      list.value = list.value.concat(res.list as T[]);
      total.value = res.total;
      status.value = res.list.length > 0 ? 'finished' : (list.value.length > 0 ? 'nomore' : 'empty');
      error.value = '';
      loading = false;
    } catch(e) {
      console.error(e);
      error.value = '' + e;
      status.value = 'error';
      loading = false;
    } finally {
      if (showGlobalLoading)
        uni.hideLoading();
    }
  }

  onPullDownRefresh(() => {
    load(true, lastParams).then(() => {
      uni.stopPullDownRefresh();
    }).catch(() => {
      uni.stopPullDownRefresh();
    });
  });
  onReachBottom(() => {
    if (status.value == 'nomore')
      return;
    load(false, lastParams);
  });

  onMounted(() => {
    if (loadWhenMounted)
      load(false, lastParams);
  })

  return {
    list,
    total,
    page,
    status,
    error,
    load,
    reload: () => load(true),
  }
}