/*

  * Copyright 1999,2006 The Apache Software Foundation.

  * 

  * 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 org.apache.commons.feedparser.tools;

 import java.text.SimpleDateFormat;

 import java.util.Date;

 import java.util.Locale;

 import java.util.TimeZone;

 /**

  * ISO 8601 date parsing utility.  Designed for parsing the ISO subset used in

  * Dublin Core, RSS 1.0, and Atom.

  * 

  * @author <a href="mailto:burton@apache.org">Kevin A. Burton (burtonator)</a>

  * @version $Id: ISO8601DateParser.java 373572 2006-01-30 19:28:41Z mvdb $

  */

 public class ISO8601DateParser {

     // 2004-06-14T19:GMT20:30Z

     // 2004-06-20T06:GMT22:01Z

     private static SimpleDateFormat df

         = new SimpleDateFormat( "yyyy-MM-dd'T'hh:mm:ssz", Locale.ENGLISH );

     // http://www.cl.cam.ac.uk/~mgk25/iso-time.html

     //    

     // http://www.intertwingly.net/wiki/pie/DateTime

     //

     // http://www.w3.org/TR/NOTE-datetime

     //

     // Different standards may need different levels of granularity in the date and

     // time, so this profile defines six levels. Standards that reference this

     // profile should specify one or more of these granularities. If a given

     // standard allows more than one granularity, it should specify the meaning of

     // the dates and times with reduced precision, for example, the result of

     // comparing two dates with different precisions.

     // The formats are as follows. Exactly the components shown here must be

     // present, with exactly this punctuation. Note that the "T" appears literally

     // in the string, to indicate the beginning of the time element, as specified in

     // ISO 8601.

     //    Year:

     //       YYYY (eg 1997)

     //    Year and month:

     //       YYYY-MM (eg 1997-07)

     //    Complete date:

     //       YYYY-MM-DD (eg 1997-07-16)

     //    Complete date plus hours and minutes:

     //       YYYY-MM-DDThh:mmTZD (eg 1997-07-16T19:20+01:00)

     //    Complete date plus hours, minutes and seconds:

     //       YYYY-MM-DDThh:mm:ssTZD (eg 1997-07-16T19:20:30+01:00)

     //    Complete date plus hours, minutes, seconds and a decimal fraction of a

     // second

     //       YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00)

     // where:

     //      YYYY = four-digit year

     //      MM   = two-digit month (01=January, etc.)

     //      DD   = two-digit day of month (01 through 31)

     //      hh   = two digits of hour (00 through 23) (am/pm NOT allowed)

     //      mm   = two digits of minute (00 through 59)

     //      ss   = two digits of second (00 through 59)

     //      s    = one or more digits representing a decimal fraction of a second

     //      TZD  = time zone designator (Z or +hh:mm or -hh:mm)

     public static Date parse( String input ) throws java.text.ParseException {

         //NOTE: SimpleDateFormat uses GMT[-+]hh:mm for the TZ which breaks

         //things a bit.  Before we go on we have to repair this.

         //this is zero time so we need to add that TZ indicator for 

         if ( input.endsWith( "Z" ) ) {

             input = input.substring( 0, input.length() - 1) + "GMT-00:00";

         } else {

             int inset = 6;

             String s0 = input.substring( 0, input.length() - inset );

             String s1 = input.substring( input.length() - inset, input.length() );

             input = s0 + "GMT" + s1;

         }

         return df.parse( input );

     }

     public static String toString( Date date ) {

         TimeZone tz = TimeZone.getTimeZone( "UTC" );

         df.setTimeZone( tz );

         String output = df.format( date );

         int inset0 = 9;

         int inset1 = 6;

         String s0 = output.substring( 0, output.length() - inset0 );

         String s1 = output.substring( output.length() - inset1, output.length() );

         String result = s0 + s1;

         result = result.replaceAll( "UTC", "+00:00" );

         return result;

     }

     public static void main( String[] args ) throws Exception {

         System.out.println( parse( "2004-05-31T09:19:31-06:00" ) );

         System.out.println( parse( "2004-06-23T17:25:31-00:00" ) );

         System.out.println( parse( "2004-06-23T17:25:31Z" ) );

         //2002-10-02T10:00:00-05:00

         System.out.println( "v: " + toString( new Date( System.currentTimeMillis() ) ) );

     }

 }