content: /*
   * Copyright (C) 2007 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.android.common;
  
  import android.text.format.Time;
  
  import java.util.Calendar;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * Helper for parsing an HTTP date.
   */
  final class LegacyHttpDateTime {
  
      /*
       * Regular expression for parsing HTTP-date.
       *
       * Wdy, DD Mon YYYY HH:MM:SS GMT
       * RFC 822, updated by RFC 1123
       *
       * Weekday, DD-Mon-YY HH:MM:SS GMT
       * RFC 850, obsoleted by RFC 1036
       *
       * Wdy Mon DD HH:MM:SS YYYY
       * ANSI C's asctime() format
       *
       * with following variations
       *
       * Wdy, DD-Mon-YYYY HH:MM:SS GMT
       * Wdy, (SP)D Mon YYYY HH:MM:SS GMT
       * Wdy,DD Mon YYYY HH:MM:SS GMT
       * Wdy, DD-Mon-YY HH:MM:SS GMT
       * Wdy, DD Mon YYYY HH:MM:SS -HHMM
       * Wdy, DD Mon YYYY HH:MM:SS
       * Wdy Mon (SP)D HH:MM:SS YYYY
       * Wdy Mon DD HH:MM:SS YYYY GMT
       * 
       * HH can be H if the first digit is zero.
       * 
       * Mon can be the full name of the month.
       */
      private static final String HTTP_DATE_RFC_REGEXP =
              "([0-9]{1,2})[- ]([A-Za-z]{3,9})[- ]([0-9]{2,4})[ ]"
              + "([0-9]{1,2}:[0-9][0-9]:[0-9][0-9])";
  
      private static final String HTTP_DATE_ANSIC_REGEXP =
              "[ ]([A-Za-z]{3,9})[ ]+([0-9]{1,2})[ ]"
              + "([0-9]{1,2}:[0-9][0-9]:[0-9][0-9])[ ]([0-9]{2,4})";
  
      /**
       * The compiled version of the HTTP-date regular expressions.
       */
      private static final Pattern HTTP_DATE_RFC_PATTERN =
              Pattern.compile(HTTP_DATE_RFC_REGEXP);
      private static final Pattern HTTP_DATE_ANSIC_PATTERN =
              Pattern.compile(HTTP_DATE_ANSIC_REGEXP);
  
      private static class TimeOfDay {
          TimeOfDay(int h, int m, int s) {
              this.hour = h;
              this.minute = m;
              this.second = s;
          }
          
          int hour;
          int minute;
          int second;
      }
  
      public static long parse(String timeString)
              throws IllegalArgumentException {
  
          int date = 1;
          int month = Calendar.JANUARY;
          int year = 1970;
          TimeOfDay timeOfDay;
  
          Matcher rfcMatcher = HTTP_DATE_RFC_PATTERN.matcher(timeString);
          if (rfcMatcher.find()) {
              date = getDate(rfcMatcher.group(1));
              month = getMonth(rfcMatcher.group(2));
              year = getYear(rfcMatcher.group(3));
              timeOfDay = getTime(rfcMatcher.group(4));
          } else {
              Matcher ansicMatcher = HTTP_DATE_ANSIC_PATTERN.matcher(timeString);
              if (ansicMatcher.find()) {
                  month = getMonth(ansicMatcher.group(1));
                  date = getDate(ansicMatcher.group(2));
                  timeOfDay = getTime(ansicMatcher.group(3));
                  year = getYear(ansicMatcher.group(4));
              } else {
                  throw new IllegalArgumentException();
              }
          }
  
          // FIXME: Y2038 BUG!
          if (year >= 2038) {
              year = 2038;
              month = Calendar.JANUARY;
              date = 1;
          }
  
          Time time = new Time(Time.TIMEZONE_UTC);
          time.set(timeOfDay.second, timeOfDay.minute, timeOfDay.hour, date,
                  month, year);
          return time.toMillis(false /* use isDst */);
      }
  
      private static int getDate(String dateString) {
          if (dateString.length() == 2) {
              return (dateString.charAt(0) - '0') * 10
                      + (dateString.charAt(1) - '0');
          } else {
              return (dateString.charAt(0) - '0');
          }
      }
  
      /*
       * jan = 9 + 0 + 13 = 22
       * feb = 5 + 4 + 1 = 10
       * mar = 12 + 0 + 17 = 29
       * apr = 0 + 15 + 17 = 32
       * may = 12 + 0 + 24 = 36
       * jun = 9 + 20 + 13 = 42
       * jul = 9 + 20 + 11 = 40
       * aug = 0 + 20 + 6 = 26
       * sep = 18 + 4 + 15 = 37
       * oct = 14 + 2 + 19 = 35
       * nov = 13 + 14 + 21 = 48
       * dec = 3 + 4 + 2 = 9
       */
      private static int getMonth(String monthString) {
          int hash = Character.toLowerCase(monthString.charAt(0)) +
                  Character.toLowerCase(monthString.charAt(1)) +
                  Character.toLowerCase(monthString.charAt(2)) - 3 * 'a';
          switch (hash) {
              case 22:
                  return Calendar.JANUARY;
              case 10:
                  return Calendar.FEBRUARY;
              case 29:
                  return Calendar.MARCH;
              case 32:
                  return Calendar.APRIL;
              case 36:
                  return Calendar.MAY;
              case 42:
                  return Calendar.JUNE;
              case 40:
                  return Calendar.JULY;
              case 26:
                  return Calendar.AUGUST;
              case 37:
                  return Calendar.SEPTEMBER;
              case 35:
                  return Calendar.OCTOBER;
              case 48:
                  return Calendar.NOVEMBER;
              case 9:
                  return Calendar.DECEMBER;
              default:
                  throw new IllegalArgumentException();
          }
      }
  
      private static int getYear(String yearString) {
          if (yearString.length() == 2) {
              int year = (yearString.charAt(0) - '0') * 10
                      + (yearString.charAt(1) - '0');
              if (year >= 70) {
                  return year + 1900;
              } else {
                  return year + 2000;
              }
          } else if (yearString.length() == 3) {
              // According to RFC 2822, three digit years should be added to 1900.
              int year = (yearString.charAt(0) - '0') * 100
                      + (yearString.charAt(1) - '0') * 10
                      + (yearString.charAt(2) - '0');
              return year + 1900;
          } else if (yearString.length() == 4) {
               return (yearString.charAt(0) - '0') * 1000
                      + (yearString.charAt(1) - '0') * 100
                      + (yearString.charAt(2) - '0') * 10
                      + (yearString.charAt(3) - '0');
          } else {
               return 1970;
          }
      }
  
      private static TimeOfDay getTime(String timeString) {
          // HH might be H
          int i = 0;
          int hour = timeString.charAt(i++) - '0';
          if (timeString.charAt(i) != ':')
              hour = hour * 10 + (timeString.charAt(i++) - '0');
          // Skip ':'
          i++;
          
          int minute = (timeString.charAt(i++) - '0') * 10
                      + (timeString.charAt(i++) - '0');
          // Skip ':'
          i++;
          
          int second = (timeString.charAt(i++) - '0') * 10
                    + (timeString.charAt(i++) - '0');
  
          return new TimeOfDay(hour, minute, second);        
      }
  }
  