movePage({ getters, commit }, { name, pageNum, direction }) {
      return new Promise(async (resolve, reject) => {
        try {
          if (pageNum == 1 && direction == 'left') {
            reject('Error cant move first page to the left');
          }
          const totalPages = getters.pageCount(name);
          if (pageNum >= totalPages && direction == 'right') {
            reject('Error cant move last page to the right');
          }
          const newPageNum = direction == 'left' ? pageNum - 1 : pageNum + 1;
          const db = fb.firestore();
          const pageUid = getters.pageItem(name, pageNum).uid;
          const newPageUid = getters.pageItem(name, newPageNum).uid;
          const pageRef = db.doc(`pages/${pageUid}`);
          const newPageRef = db.doc(`pages/${newPageUid}`);
          await db.runTransaction(async transaction => {
            const pageDoc = await transaction.get(pageRef);
            const newPageDoc = await transaction.get(newPageRef);
            const position = pageDoc.get('position');
            const newPosition = newPageDoc.get('position');
            await transaction.update(pageRef, { position: newPosition });
            await transaction.update(newPageRef, { position });
          });
          commit('exchangePosition', { name, pageNum, newPageNum });
          resolve(newPageNum);
        } catch (error) {
          console.error('Error move page: ', error);
          reject(error);
        }
      });
    },