strapi/packages/strapi-plugin-content-manager/admin/src/components/Group/reducer.js

import { fromJS } from 'immutable';

const initialState = fromJS({ collapses: [] });

function reducer(state, action) {
  switch (action.type) {
    case 'ADD_NEW_FIELD':
      return state.update('collapses', list => {
        return list
          .map(obj => obj.update('isOpen', () => false))
          .push(fromJS({ isOpen: true }));
      });
    case 'COLLAPSE_ALL':
      return state.update('collapses', list =>
        list.map(obj => obj.update('isOpen', () => false))
      );
    case 'TOGGLE_COLLAPSE':
      return state.update('collapses', list => {
        return list.map((obj, index) => {
          if (index === action.index) {
            return obj.update('isOpen', v => !v);
          }

          return obj.update('isOpen', () => false);
        });
      });
    case 'REMOVE_COLLAPSE':
      return state
        .removeIn(['collapses', action.index])
        .update('collapses', list => list.map(obj => obj.set('isOpen', false)))
        .update('collapses', list => {
          if (action.shouldAddEmptyField) {
            return list.push(fromJS({ isOpen: true }));
          }

          return list;
        });
    default:
      return state;
  }
}

export default reducer;
export { initialState };