import { ref, reactive } from "vue";
import type { EmailSummary } from "@/types/email";
import type { GetEmailSummaryPageParams } from "@/service/email";
import { getEmailSummaryPageApi } from "@/service/email";

const queryParams = reactive<GetEmailSummaryPageParams>({
  folderId: "",
  page: 1,
  pageSize: 10
});

const loading = ref(false);
const emailList = ref<EmailSummary[]>([]);
const total = ref(0);

const prefetchCache = ref<{
  page: number | null;
  data: EmailSummary[];
  used: boolean; // ✅ 用于标记是否已经部分使用
}>({
  page: null,
  data: [],
  used: false
});

export function useEmailListManager() {
  const fetchData = async () => {
    if (!queryParams.folderId) return;

    const { page, pageSize, folderId } = queryParams;

    // ✅ 判断是否可以安全使用缓存
    const canUseCache = prefetchCache.value.page === page && prefetchCache.value.data.length > 0 && !prefetchCache.value.used;

    if (canUseCache) {
      console.log(`Using cached data for page ${page}`);
      emailList.value = [...prefetchCache.value.data];
    } else {
      loading.value = true;
      try {
        const res = await getEmailSummaryPageApi({ folderId, page, pageSize });
        const pageData = res.data;
        emailList.value = pageData.record;
        total.value = pageData.total;
      } finally {
        loading.value = false;
      }
    }

    // ✅ 预取下一页（如果有）
    const maxPage = Math.ceil(total.value / pageSize);
    const nextPage = page + 1;
    if (nextPage <= maxPage) {
      prefetchPageData(nextPage, folderId, pageSize);
    } else {
      clearPrefetch();
    }
  };

  const prefetchPageData = async (page: number, folderId: string, pageSize: number) => {
    try {
      const res = await getEmailSummaryPageApi({ folderId, page, pageSize });
      prefetchCache.value = {
        page,
        data: res.data.record,
        used: false
      };
    } catch {
      clearPrefetch();
    }
  };

  const clearPrefetch = () => {
    prefetchCache.value = {
      page: null,
      data: [],
      used: false
    };
  };

  const removeAndFill = async (idsToRemove: string[]) => {
    idsToRemove.forEach((id) => {
      const idx = emailList.value.findIndex((item) => item.id === id);
      if (idx !== -1) {
        emailList.value.splice(idx, 1);
        total.value = Math.max(0, total.value - 1);
      }
    });

    // ✅ 从预取数据补足当前页
    while (emailList.value.length < queryParams.pageSize && prefetchCache.value.data.length > 0) {
      emailList.value.push(prefetchCache.value.data.shift()!);
      prefetchCache.value.used = true; // ✅ 标记：缓存被用过
    }

    // ✅ 如果仍不足，尝试翻页请求新数据
    const maxPage = Math.ceil(total.value / queryParams.pageSize);
    if (emailList.value.length < queryParams.pageSize && queryParams.page < maxPage) {
      queryParams.page++;
      await fetchData(); // 内部已判断是否重新请求
    }
  };

  const resetData = () => {
    queryParams.page = 1;
    queryParams.pageSize = 10;
    total.value = 0;
    emailList.value = [];
    clearPrefetch();
  };

  return {
    queryParams,
    emailList,
    loading,
    total,
    fetchData,
    removeAndFill,
    resetData,
    cacheEmailList: prefetchCache // 👈 新增这一行
  };
}