Time calculation

main.dart

import 'dart:core';

// Define the start and end times
// These can now be "h:mm AM/PM" or "HH:mm"
String startTimeStr = "8:46 AM";
String endTimeStr = "5:30 PM";

// Example for 24-hour format:
// String startTimeStr = "08:46";
// String endTimeStr = "17:30";

// Example for mixed formats:
// String startTimeStr = "8:46 AM";
// String endTimeStr = "17:30";

/// Parses a time string, supporting both "h:mm AM/PM" (12-hour)
/// and "HH:mm" (24-hour) formats.
///
/// Returns a [DateTime] object with a fixed arbitrary date (Jan 1, 2025)
/// and the parsed time, or `null` if the string cannot be parsed.
DateTime? parseTime(String timeStr) {
  try {
    final timeStrUpper = timeStr.toUpperCase();
    final is12HourFormat =
        timeStrUpper.contains("AM") || timeStrUpper.contains("PM");

    int hour;
    int minute;

    if (is12HourFormat) {
      final parts = timeStr.split(" ");
      if (parts.length != 2) return null; // Expected "time meridian"

      final hmParts = parts[0].split(":");
      if (hmParts.length != 2) return null; // Expected "h:mm"

      hour = int.parse(hmParts[0]);
      minute = int.parse(hmParts[1]);
      String meridian = parts[1].toUpperCase();

      if (meridian == "PM" && hour != 12) {
        hour += 12;
      } else if (meridian == "AM" && hour == 12) {
        hour = 0; // 12 AM (midnight) is 00:xx in 24-hour format
      }

      // Basic validation for parsed hour/minute values
      if (hour < 0 || hour > 23 || minute < 0 || minute > 59) {
        return null;
      }
    } else {
      // Assume 24-hour format (HH:mm)
      final hmParts = timeStr.split(":");
      if (hmParts.length != 2) return null; // Expected "HH:mm"

      hour = int.parse(hmParts[0]);
      minute = int.parse(hmParts[1]);

      // Basic validation for parsed hour/minute values
      if (hour < 0 || hour > 23 || minute < 0 || minute > 59) {
        return null;
      }
    }

    // Use a fixed date; only the time component is relevant for duration.
    return DateTime(2025, 1, 1, hour, minute);
  } on FormatException {
    // Catch errors from int.parse if the number format is invalid
    return null;
  } catch (e) {
    // Catch any other unexpected errors during parsing
    return null;
  }
}

void main() {


  DateTime? startTime = parseTime(startTimeStr);
  DateTime? endTime = parseTime(endTimeStr);

  if (startTime == null) {
    print(
      "Error: Could not parse start time '$startTimeStr'. Please use 'h:mm AM/PM' or 'HH:mm' format.",
    );
    return;
  }
  if (endTime == null) {
    print(
      "Error: Could not parse end time '$endTimeStr'. Please use 'h:mm AM/PM' or 'HH:mm' format.",
    );
    return;
  }

  // Calculate difference
  Duration difference = endTime.difference(startTime);
  int totalMinutes = difference.inMinutes;

  print(
    "The number of minutes from $startTimeStr to $endTimeStr is $totalMinutes minutes.",
  );
}