parseDateTime static method

Implementation

static DateTime? parseDateTime(dynamic input) {
  if (input is DateTime) {
    return input;
  } else if (input is int) {
    return DateTime.fromMillisecondsSinceEpoch(input * 1000);
  } else if (input is String) {
    int? intValue = int.tryParse(input);
    if (intValue != null) {
      return DateTime.fromMillisecondsSinceEpoch(intValue * 1000);
    } else {
      // try parse ISO format
      try {
        return DateTime.parse(input);
      } on FormatException catch (_, e) {}

      // try http date format e.g Thu, 23 Jan 2022 05:05:05 GMT+0200

      // Note that HttpDate parser won't work if we have an offset e.g GMT+0700 or GMT -02:00
      // we'll remove the offset, parse the date, then adjust manually afterward
      String updatedInput = input;
      Duration? offset;
      bool isNegativeOffset = false;
      RegExpMatch? match =
          RegExp(r'.+ GMT(?<offset>\s?([+-])(\d{2}):?(\d{2}))$')
              .firstMatch(input);
      if (match != null) {
        // remove any offset from the string so we can parse it
        String rawOffset = match.namedGroup('offset')!;
        updatedInput = updatedInput.substring(0, input.indexOf(rawOffset));
        //print(updatedInput);

        isNegativeOffset = match.group(2) == '-' ? true : false;
        int hourOffset = int.parse(match.group(3)!);
        int minuteOffset = int.parse(match.group(4)!);

        offset = Duration(hours: hourOffset, minutes: minuteOffset);
      }
      try {
        DateTime gmtDateTime = HttpDate.parse(updatedInput);
        // adjust the offset
        if (offset != null) {
          gmtDateTime = isNegativeOffset
              ? gmtDateTime.add(offset)
              : gmtDateTime.subtract(offset);
          //print(parsedDateTime);
        }
        // we parsed the date as GMT, need to convert to our local time
        return gmtDateTime;
      } catch (e) {}
    }
  }
  return null;
}