the following code uses a variable called "index" to refer to a parameter of the "map" function in javascript. The "index" variable is used to get the previous and next item from the sortedStations array. How can i modify this code to respect the bounds of the sortedStations array:

 const { routeFetchedById, direction, updateStationsSchedule } = this.props;
 const {
 scheduleTargetTimes: { defaultTime },
 } = this.state;
 if (routeFetchedById === ROUTE\_BY\_ID\_MISSING) return;
 const sortedStations = sortBy(routeFetchedById[direction], 'stationOrder');
 const wayBack = direction === ROUTE\_DIRECTIONS.WAYBACK;
 const initPayload = sortedStations.map((station, index) => ({
 stationId: station.id,
 stationOrder: station.stationOrder,
 schedule: ROUTE\_WORK\_DAYS.map(day => ({
 day,
 time: moment(defaultTime).add(wayBack ? travelTime(sortedStations[index - 1], sortedStations[index]) : travelTime(sortedStations[index], sortedStations[index - 1])).format(SCHEDULE\_SERVER\_TIME\_FORMAT),
 })),
 }));
 updateStationsSchedule(routeFetchedById.id, direction, initPayload);
user
Certainly, I'd be happy to help you modify the code to respect the bounds of the `sortedStations` array. Here's how you can do it:

1. Start by checking if the current index is within the bounds of the array:

   ```javascript
   const index = (index + sortedStations.length) % sortedStations.length;
   ```

   This expression calculates the "wrapped" index, wrapping around to the beginning of the array if it goes beyond the end.

2. Then, use this wrapped index to check if we're on the last or first element of the array:

   ```javascript
   if (index === sortedStations.length - 1) { // last element
     // handle special case here
   } else if (index === 0) { // first element
     // handle special case here
   } else { // middle elements
     // get the previous and next items from the sortedStations array
     const prevStation = sortedStations[index - 1];
     const nextStation = sortedStations[index];
   }
   ```

In the example code you provided, this would look something like this:

```javascript
const { routeFetchedById, direction, updateStationsSchedule } = this.props;
const {
  scheduleTargetTimes: { defaultTime },
} = this.state;

if (routeFetchedById === ROUTE_BY_ID_MISSING) return;
const sortedStations = sortBy(routeFetchedById[direction], 'stationOrder');
const wayBack = direction === ROUTE_DIRECTIONS.WAYBACK;
const initPayload = sortedStations.map((station, index) => ({
  stationId: station.id,
  stationOrder: station.stationOrder,
  schedule: ROUTE_WORK_DAYS.map(day => ({
    day,
    time: moment(defaultTime)
      .add(wayBack ? travelTime(sortedStations[index - 1], sortedStations[index]) : travelTime(sortedStations[index], sortedStations[index - 1])
      )
      .format(SCHEDULE_SERVER_TIME_FORMAT),
  })),
}));

updateStationsSchedule(routeFetchedById.id, direction, initPayload);

// Wrap the index
const wrappedIndex = (index + sortedStations.length) % sortedStations.length;

// Handle first and last element
if (wrappedIndex === sortedStations.length - 1) {
  // Handle special case for the last element
} else if (wrappedIndex === 0) {
  // Handle special case for the first element
} else {
  // Get previous and next station as before
  const prevStation = sortedStations[wrappedIndex - 1];
  const nextStation = sortedStations[wrappedIndex];
}
```

In this example, I've shown how to get the index of the station, wrap it, and how to distinguish the beginning or end if the station order is wrapped around. You can add your special logic for the first and last station in the "if" statements.
assistant
the following code uses a variable called "index" to refer to a parameter of the "map" function in javascript. The "index" variable is used to get the previous and next item from the sortedStations array. How can i modify this code to respect the bounds of the sortedStations array:

 const { routeFetchedById, direction, updateStationsSchedule } = this.props;
 const {
 scheduleTargetTimes: { defaultTime },
 } = this.state;
 if (routeFetchedById === ROUTE\_BY\_ID\_MISSING) return;
 const sortedStations = sortBy(routeFetchedById[direction], 'stationOrder');
 const wayBack = direction === ROUTE\_DIRECTIONS.WAYBACK;
 const initPayload = sortedStations.map((station, index) => ({
 stationId: station.id,
 stationOrder: station.stationOrder,
 schedule: ROUTE\_WORK\_DAYS.map(day => ({
 day,
 time: moment(defaultTime).add(wayBack ? travelTime(sortedStations[index - 1], sortedStations[index]) : travelTime(sortedStations[index], sortedStations[index - 1])).format(SCHEDULE\_SERVER\_TIME\_FORMAT),
 })),
 }));
 updateStationsSchedule(routeFetchedById.id, direction, initPayload);
user
To respect the bounds of the sortedStations array, you can add conditions to check if the current index is at the start or end of the array. Here's the modified code:

```javascript
const { routeFetchedById, direction, updateStationsSchedule } = this.props;
const {
  scheduleTargetTimes: { defaultTime },
} = this.state;
if (routeFetchedById === ROUTE_BY_ID_MISSING) return;
const sortedStations = sortBy(routeFetchedById[direction], 'stationOrder');
const wayBack = direction === ROUTE_DIRECTIONS.WAYBACK;
const initPayload = sortedStations.map((station, index) => {
  let prevStation = index > 0 ? sortedStations[index - 1] : null;
  let nextStation = index < sortedStations.length - 1 ? sortedStations[index + 1] : null;

  let travelTimeValue;
  if (wayBack) {
    if (prevStation) {
      travelTimeValue = travelTime(prevStation, station);
    } else {
      travelTimeValue = moment.duration(0);
    }
  } else {
    if (nextStation) {
      travelTimeValue = travelTime(station, nextStation);
    } else {
      travelTimeValue = moment.duration(0);
    }
  }

  return {
    stationId: station.id,
    stationOrder: station.stationOrder,
    schedule: ROUTE_WORK_DAYS.map(day => ({
      day,
      time: moment(defaultTime).add(travelTimeValue).format(SCHEDULE_SERVER_TIME_FORMAT),
    })),
  };
});
updateStationsSchedule(routeFetchedById.id, direction, initPayload);
```

In this code, I've added checks to see if the index is at the beginning or the end of the array. If it is, then the `prevStation` or `nextStation` variables will be set to `null`. The `travelTimeValue` variable is now calculated conditionally based on the existence of the `prevStation` or `nextStation`. If there's no previous or next station, the travel time will be set to zero (moment.duration(0)).
assistant