text: export class GetMonthIncrementedOrDecrementedService {
      static go(plusOrMinusOne, { monthIndex, year }) {
          let data = this.__getMonthIndexAndYearPreparedIfEnteringNextOrPreviousYear(plusOrMinusOne, monthIndex, year);
          data.monthIndex += plusOrMinusOne;
          return data;
      }
      static __getMonthIndexAndYearPreparedIfEnteringNextOrPreviousYear(plusOrMinusOne, monthIndex, year) {
          if (this.__enteringPreviousYear(plusOrMinusOne, monthIndex)) {
              --year;
              return { monthIndex: 12, year };
          }
          if (this.__enteringNextYear(plusOrMinusOne, monthIndex)) {
              ++year;
              return { monthIndex: -1, year };
          }
          return { monthIndex, year };
      }
      static __enteringPreviousYear(plusOrMinusOne, monthIndex) {
          return (plusOrMinusOne === -1 && monthIndex === 0);
      }
      static __enteringNextYear(plusOrMinusOne, monthIndex) {
          return (plusOrMinusOne === 1 && monthIndex === 11);
      }
  }
  