getAvailableSlots static method

List<DateTimeRange<DateTime>> getAvailableSlots(DateTime selectedDateTime, String messageTimeZone, String localTimeZone, Map<String, List<TimeRange>>? availability,)

Implementation

static List<DateTimeRange> getAvailableSlots(
  DateTime selectedDateTime,
  String messageTimeZone,
  String localTimeZone,
  Map<String, List<TimeRange>>? availability,
) {
  // initializing start time and end time in local time zone
  DateTime localStartTime = selectedDateTime;
  DateTime localEndTime = selectedDateTime.add(
    const Duration(hours: 23, minutes: 59, seconds: 59),
  );
  List<DateTimeRange> totalAvailableSlots = [];

  if (messageTimeZone == localTimeZone) {
    List<TimeRange> availableSlots =
        availability?[weekdays[localStartTime.weekday - 1]] ?? [];

    for (TimeRange start in availableSlots) {
      DateTime startTime = localStartTime.add(
        Duration(
          hours: int.parse(start.from.substring(0, 2)),
          minutes: int.parse(start.from.substring(2)),
        ),
      );

      DateTime endTime = localStartTime.add(
        Duration(
          hours: int.parse(start.to.substring(0, 2)),
          minutes: int.parse(start.to.substring(2)),
        ),
      );

      if (startTime.isAfter(localStartTime) ||
          startTime.isAtSameMomentAs(localStartTime) &&
              endTime.isAfter(startTime)) {
        totalAvailableSlots.add(
          DateTimeRange(start: startTime.toLocal(), end: endTime.toLocal()),
        );
      }
    }
  } else {
    // converting today and next day to provided time zone
    DateTime internationalStartTime = getConvertedTime(
      localStartTime,
      messageTimeZone,
    );
    DateTime internationalEndTime = getConvertedTime(
      localEndTime,
      messageTimeZone,
    );

    List<TimeRange> availableSlots1 =
        availability?[weekdays[internationalStartTime.weekday - 1]] ?? [];

    DateTime baseStart = internationalStartTime.subtract(
      Duration(
        hours: internationalStartTime.hour,
        minutes: internationalStartTime.minute,
        seconds: internationalStartTime.second,
        microseconds: internationalStartTime.microsecond,
        milliseconds: internationalStartTime.millisecond,
      ),
    );

    for (TimeRange start in availableSlots1) {
      DateTime startTime = baseStart.add(
        Duration(
          hours: int.parse(start.from.substring(0, 2)),
          minutes: int.parse(start.from.substring(2)),
        ),
      );

      DateTime endTime = baseStart.add(
        Duration(
          hours: int.parse(start.to.substring(0, 2)),
          minutes: int.parse(start.to.substring(2)),
        ),
      );

      startTime = SchedulerUtils.getConvertedTime(
        startTime.toLocal(),
        localTimeZone,
      );
      endTime = SchedulerUtils.getConvertedTime(
        endTime.toLocal(),
        localTimeZone,
      );

      if ((startTime.day == selectedDateTime.day ||
              endTime.day == selectedDateTime.day) &&
          endTime.isAfter(startTime)) {
        if (startTime.day < selectedDateTime.day &&
            localStartTime.isBefore(endTime)) {
          startTime = localStartTime;
        }
        if (endTime.day > selectedDateTime.day &&
            localEndTime.isAfter(startTime)) {
          endTime = localEndTime;
        }

        totalAvailableSlots.add(
          DateTimeRange(start: startTime, end: endTime),
        );
      }
    }

    if (internationalEndTime.day > internationalStartTime.day) {
      List<TimeRange> availableSlots2 =
          availability?[weekdays[internationalEndTime.weekday - 1]] ?? [];

      DateTime baseEnd = internationalEndTime.subtract(
        Duration(
          hours: internationalEndTime.hour,
          minutes: internationalEndTime.minute,
          seconds: internationalEndTime.second,
          microseconds: internationalEndTime.microsecond,
          milliseconds: internationalEndTime.millisecond,
        ),
      );

      for (TimeRange start in availableSlots2) {
        DateTime startTime = baseEnd.add(
          Duration(
            hours: int.parse(start.from.substring(0, 2)),
            minutes: int.parse(start.from.substring(2)),
          ),
        );

        DateTime endTime = baseEnd.add(
          Duration(
            hours: int.parse(start.to.substring(0, 2)),
            minutes: int.parse(start.to.substring(2)),
          ),
        );

        startTime = SchedulerUtils.getConvertedTime(
          startTime.toLocal(),
          localTimeZone,
        );
        endTime = SchedulerUtils.getConvertedTime(
          endTime.toLocal(),
          localTimeZone,
        );
        if ((startTime.day == selectedDateTime.day ||
                endTime.day == selectedDateTime.day) &&
            endTime.isAfter(startTime)) {
          if (startTime.day < selectedDateTime.day) {
            startTime = localStartTime;
          }
          if (endTime.day > selectedDateTime.day) {
            endTime = localEndTime;
          }
          totalAvailableSlots.add(
            DateTimeRange(start: startTime, end: endTime),
          );
        }
      }
    }
  }
  return totalAvailableSlots;
}