static DateTime parse()

in lib/src/http_date.dart [84:221]
129 lines of code
16 McCabe index (conditional complexity)

  static DateTime parse(String date) {
    final int SP = 32;
    const List wkdays = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];
    const List weekdays = [
      "Monday",
      "Tuesday",
      "Wednesday",
      "Thursday",
      "Friday",
      "Saturday",
      "Sunday"
    ];
    const List months = [
      "Jan",
      "Feb",
      "Mar",
      "Apr",
      "May",
      "Jun",
      "Jul",
      "Aug",
      "Sep",
      "Oct",
      "Nov",
      "Dec"
    ];

    final int formatRfc1123 = 0;
    final int formatRfc850 = 1;
    final int formatAsctime = 2;

    int index = 0;
    String tmp;
    int format;

    void expect(String s) {
      if (date.length - index < s.length) {
        throw HttpException("Invalid HTTP date $date");
      }
      String tmp = date.substring(index, index + s.length);
      if (tmp != s) {
        throw HttpException("Invalid HTTP date $date");
      }
      index += s.length;
    }

    int expectWeekday() {
      int weekday;
      // The formatting of the weekday signals the format of the date string.
      int pos = date.indexOf(",", index);
      if (pos == -1) {
        int pos = date.indexOf(" ", index);
        if (pos == -1) throw HttpException("Invalid HTTP date $date");
        tmp = date.substring(index, pos);
        index = pos + 1;
        weekday = wkdays.indexOf(tmp);
        if (weekday != -1) {
          format = formatAsctime;
          return weekday;
        }
      } else {
        tmp = date.substring(index, pos);
        index = pos + 1;
        weekday = wkdays.indexOf(tmp);
        if (weekday != -1) {
          format = formatRfc1123;
          return weekday;
        }
        weekday = weekdays.indexOf(tmp);
        if (weekday != -1) {
          format = formatRfc850;
          return weekday;
        }
      }
      throw HttpException("Invalid HTTP date $date");
    }

    int expectMonth(String separator) {
      int pos = date.indexOf(separator, index);
      if (pos - index != 3) throw HttpException("Invalid HTTP date $date");
      tmp = date.substring(index, pos);
      index = pos + 1;
      int month = months.indexOf(tmp);
      if (month != -1) return month;
      throw HttpException("Invalid HTTP date $date");
    }

    int expectNum(String separator) {
      int pos;
      if (separator.isNotEmpty) {
        pos = date.indexOf(separator, index);
      } else {
        pos = date.length;
      }
      String tmp = date.substring(index, pos);
      index = pos + separator.length;
      try {
        int value = int.parse(tmp);
        return value;
      } on FormatException {
        throw HttpException("Invalid HTTP date $date");
      }
    }

    void expectEnd() {
      if (index != date.length) {
        throw HttpException("Invalid HTTP date $date");
      }
    }

    expectWeekday();
    int day;
    int month;
    int year;
    int hours;
    int minutes;
    int seconds;
    if (format == formatAsctime) {
      month = expectMonth(" ");
      if (date.codeUnitAt(index) == SP) index++;
      day = expectNum(" ");
      hours = expectNum(":");
      minutes = expectNum(":");
      seconds = expectNum(" ");
      year = expectNum("");
    } else {
      expect(" ");
      day = expectNum(format == formatRfc1123 ? " " : "-");
      month = expectMonth(format == formatRfc1123 ? " " : "-");
      year = expectNum(" ");
      hours = expectNum(":");
      minutes = expectNum(":");
      seconds = expectNum(" ");
      expect("GMT");
    }
    expectEnd();
    return DateTime.utc(year, month + 1, day, hours, minutes, seconds, 0);
  }