export function handleComponentDrop()

in superset-frontend/src/dashboard/actions/dashboardLayout.js [172:268]
79 lines of code
27 McCabe index (conditional complexity)

export function handleComponentDrop(dropResult) {
  return (dispatch, getState) => {
    const overflowsParent = dropOverflowsParent(
      dropResult,
      getState().dashboardLayout.present,
    );

    if (overflowsParent) {
      return dispatch(
        addWarningToast(
          t(
            `There is not enough space for this component. Try decreasing its width, or increasing the destination width.`,
          ),
        ),
      );
    }

    const { source, destination } = dropResult;
    const droppedOnRoot = destination && destination.id === DASHBOARD_ROOT_ID;
    const isNewComponent = source.id === NEW_COMPONENTS_SOURCE_ID;
    const dashboardRoot = getState().dashboardLayout.present[DASHBOARD_ROOT_ID];
    const rootChildId =
      dashboardRoot && dashboardRoot.children ? dashboardRoot.children[0] : '';

    if (droppedOnRoot) {
      dispatch(createTopLevelTabs(dropResult));
    } else if (destination && isNewComponent) {
      dispatch(createComponent(dropResult));
    } else if (
      // Add additional allow-to-drop logic for tag/tags source.
      // We only allow
      // - top-level tab => top-level tab: rearrange top-level tab order
      // - nested tab => top-level tab: allow row tab become top-level tab
      // Dashboard does not allow top-level tab become nested tab, to avoid
      // nested tab inside nested tab.
      source.type === TABS_TYPE &&
      destination.type === TABS_TYPE &&
      source.id === rootChildId &&
      destination.id !== rootChildId
    ) {
      return dispatch(
        addWarningToast(t('Can not move top level tab into nested tabs')),
      );
    } else if (
      destination &&
      source &&
      !(
        // ensure it has moved
        (destination.id === source.id && destination.index === source.index)
      )
    ) {
      dispatch(moveComponent(dropResult));
    }

    // call getState() again down here in case redux state is stale after
    // previous dispatch(es)
    const { dashboardFilters, dashboardLayout: undoableLayout } = getState();

    // if we moved a child from a Tab or Row parent and it was the only child, delete the parent.
    if (!isNewComponent) {
      const { present: layout } = undoableLayout;
      const sourceComponent = layout[source.id] || {};
      const destinationComponent = layout[destination.id] || {};
      if (
        (sourceComponent.type === TABS_TYPE ||
          sourceComponent.type === ROW_TYPE) &&
        sourceComponent.children &&
        sourceComponent.children.length === 0
      ) {
        const parentId = findParentId({
          childId: source.id,
          layout,
        });
        dispatch(deleteComponent(source.id, parentId));
      }

      // show warning if item has been moved between different scope
      if (
        isInDifferentFilterScopes({
          dashboardFilters,
          source: (sourceComponent.parents || []).concat(source.id),
          destination: (destinationComponent.parents || []).concat(
            destination.id,
          ),
        })
      ) {
        dispatch(
          addWarningToast(
            t('This chart has been moved to a different filter scope.'),
          ),
        );
      }
    }

    return null;
  };
}