import { computed, ref } from "vue";
import { isRequestCancelled } from "@/services/api/request-controller.js";
import { getRequestErrorMessage } from "@/services/api/request-error-message.js";

export const useBatchDeletion = ({
  items,
  visibleItems = items,
  getId = (item) => item?.id,
  canDelete = (item) => item?.canDelete === true,
  deleteOne,
  resourceName,
  isActive = () => true,
  onEmpty = () => {},
}) => {
  const selectionMode = ref(false);
  const selectedIds = ref([]);
  const confirmationVisible = ref(false);
  const deleting = ref(false);
  const notice = ref("");
  const error = ref("");

  const deletableItems = computed(() => visibleItems.value.filter(canDelete));
  const allSelected = computed(
    () =>
      deletableItems.value.length > 0 &&
      deletableItems.value.every((item) => selectedIds.value.includes(getId(item))),
  );
  const selectedCount = computed(() => selectedIds.value.length);
  const confirmationMessage = computed(
    () =>
      `将选中的 ${selectedCount.value} 条${resourceName}移入回收站；管理员可在保留期内恢复。`,
  );

  const clearFeedback = () => {
    notice.value = "";
    error.value = "";
  };
  const exitSelectionMode = () => {
    selectionMode.value = false;
    selectedIds.value = [];
    confirmationVisible.value = false;
  };
  const enterSelectionMode = () => {
    if (!deletableItems.value.length || deleting.value) return;
    clearFeedback();
    selectedIds.value = [];
    selectionMode.value = true;
  };
  const isSelected = (item) => selectedIds.value.includes(getId(item));
  const toggleSelection = (item) => {
    if (!selectionMode.value || !canDelete(item) || deleting.value) return;
    const id = getId(item);
    selectedIds.value = isSelected(item)
      ? selectedIds.value.filter((selectedId) => selectedId !== id)
      : [...selectedIds.value, id];
    clearFeedback();
  };
  const toggleAll = () => {
    if (!selectionMode.value || deleting.value) return;
    selectedIds.value = allSelected.value ? [] : deletableItems.value.map(getId);
    clearFeedback();
  };
  const requestDelete = () => {
    if (!selectionMode.value || !selectedIds.value.length || deleting.value) return;
    clearFeedback();
    confirmationVisible.value = true;
  };
  const cancelDelete = () => {
    if (!deleting.value) confirmationVisible.value = false;
  };
  const confirmDelete = async () => {
    if (!selectionMode.value || !selectedIds.value.length || deleting.value) return;
    const pendingIds = selectedIds.value.slice();
    deleting.value = true;
    clearFeedback();
    let deletedCount = 0;
    let failedRequest = null;
    try {
      for (const id of pendingIds) {
        const target = items.value.find((item) => getId(item) === id);
        if (!target || !canDelete(target)) continue;
        try {
          await deleteOne(target);
        } catch (cause) {
          failedRequest = cause;
          break;
        }
        if (!isActive()) return;
        deletedCount += 1;
        items.value = items.value.filter((item) => getId(item) !== id);
        selectedIds.value = selectedIds.value.filter((selectedId) => selectedId !== id);
      }
      if (!isActive()) return;
      confirmationVisible.value = false;
      if (failedRequest && !isRequestCancelled(failedRequest)) {
        const failureCopy = getRequestErrorMessage(
          failedRequest,
          `剩余${resourceName}删除失败，请稍后重试。`,
        );
        error.value = deletedCount ? `已删除 ${deletedCount} 条；${failureCopy}` : failureCopy;
      } else if (deletedCount) {
        notice.value = `已删除 ${deletedCount} 条${resourceName}。`;
      }
      if (!items.value.length) {
        exitSelectionMode();
        onEmpty();
      } else if (!selectedIds.value.length) {
        selectionMode.value = false;
      }
    } finally {
      if (isActive()) deleting.value = false;
    }
  };

  return {
    selectionMode,
    selectedIds,
    selectedCount,
    deletableItems,
    allSelected,
    confirmationVisible,
    confirmationMessage,
    deleting,
    notice,
    error,
    enterSelectionMode,
    exitSelectionMode,
    isSelected,
    toggleSelection,
    toggleAll,
    requestDelete,
    cancelDelete,
    confirmDelete,
  };
};