/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You 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.lang3.time;

 import java.text.DateFormat;

 import java.text.Format;

 import java.text.SimpleDateFormat;

 import java.util.Arrays;

 import java.util.Locale;

 import java.util.TimeZone;

 import java.util.concurrent.ConcurrentHashMap;

 import java.util.concurrent.ConcurrentMap;

 /**

  * <p>FormatCache is a cache and factory for {@link Format}s.</p>

  * 

  * @since 3.0

  * @version $Id: FormatCache 892161 2009-12-18 07:21:10Z  $

  */

 // TODO: Before making public move from getDateTimeInstance(Integer,...) to int; or some other approach.

 abstract class FormatCache<F extends Format> {

     /**

      * No date or no time.  Used in same parameters as DateFormat.SHORT or DateFormat.LONG

      */

     static final int NONE= -1;

     private final ConcurrentMap<MultipartKey, F> cInstanceCache 

         = new ConcurrentHashMap<MultipartKey, F>(7);

     private static final ConcurrentMap<MultipartKey, String> cDateTimeInstanceCache 

         = new ConcurrentHashMap<MultipartKey, String>(7);

     /**

      * <p>Gets a formatter instance using the default pattern in the

      * default timezone and locale.</p>

      * 

      * @return a date/time formatter

      */

     public F getInstance() {

         return getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT, TimeZone.getDefault(), Locale.getDefault());

     }

     /**

      * <p>Gets a formatter instance using the specified pattern, time zone

      * and locale.</p>

      * 

      * @param pattern  {@link java.text.SimpleDateFormat} compatible

      *  pattern

      * @param timeZone  the non-null time zone

      * @param locale  the non-null locale

      * @return a pattern based date/time formatter

      * @throws IllegalArgumentException if pattern is invalid

      *  or <code>null</code>

      */

     public F getInstance(final String pattern, TimeZone timeZone, Locale locale) {

         if (pattern == null) {

             throw new NullPointerException("pattern must not be null");

         }

         if (timeZone == null) {

             timeZone = TimeZone.getDefault();

         }

         if (locale == null) {

             locale = Locale.getDefault();

         }

         final MultipartKey key = new MultipartKey(pattern, timeZone, locale);

         F format = cInstanceCache.get(key);

         if (format == null) {           

             format = createInstance(pattern, timeZone, locale);

             final F previousValue= cInstanceCache.putIfAbsent(key, format);

             if (previousValue != null) {

                 // another thread snuck in and did the same work

                 // we should return the instance that is in ConcurrentMap

                 format= previousValue;              

             }

         }

         return format;

     }

     /**

      * <p>Create a format instance using the specified pattern, time zone

      * and locale.</p>

      * 

      * @param pattern  {@link java.text.SimpleDateFormat} compatible pattern, this will not be null.

      * @param timeZone  time zone, this will not be null.

      * @param locale  locale, this will not be null.

      * @return a pattern based date/time formatter

      * @throws IllegalArgumentException if pattern is invalid

      *  or <code>null</code>

      */

     abstract protected F createInstance(String pattern, TimeZone timeZone, Locale locale);

     /**

      * <p>Gets a date/time formatter instance using the specified style,

      * time zone and locale.</p>

      * 

      * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT

      * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT

      * @param timeZone  optional time zone, overrides time zone of

      *  formatted date

      * @param locale  optional locale, overrides system locale

      * @return a localized standard date/time formatter

      * @throws IllegalArgumentException if the Locale has no date/time

      *  pattern defined

      */

     public F getDateTimeInstance(final Integer dateStyle, final Integer timeStyle, final TimeZone timeZone, Locale locale) {

         if (locale == null) {

             locale = Locale.getDefault();

         }

         final String pattern = getPatternForStyle(dateStyle, timeStyle, locale);

         return getInstance(pattern, timeZone, locale);

     }

     /**

      * <p>Gets a date/time format for the specified styles and locale.</p>

      * 

      * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT, null indicates no date in format

      * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT, null indicates no time in format

      * @param locale  The non-null locale of the desired format

      * @return a localized standard date/time format

      * @throws IllegalArgumentException if the Locale has no date/time pattern defined

      */

     public static String getPatternForStyle(final Integer dateStyle, final Integer timeStyle, final Locale locale) {

         final MultipartKey key = new MultipartKey(dateStyle, timeStyle, locale);

         String pattern = cDateTimeInstanceCache.get(key);

         if (pattern == null) {

             try {

                 DateFormat formatter;

                 if (dateStyle == null) {

                     formatter = DateFormat.getTimeInstance(timeStyle.intValue(), locale);                    

                 }

                 else if (timeStyle == null) {

                     formatter = DateFormat.getDateInstance(dateStyle.intValue(), locale);                    

                 }

                 else {

                     formatter = DateFormat.getDateTimeInstance(dateStyle.intValue(), timeStyle.intValue(), locale);

                 }

                 pattern = ((SimpleDateFormat)formatter).toPattern();

                 final String previous = cDateTimeInstanceCache.putIfAbsent(key, pattern);

                 if (previous != null) {

                     // even though it doesn't matter if another thread put the pattern

                     // it's still good practice to return the String instance that is

                     // actually in the ConcurrentMap

                     pattern= previous;

                 }

             } catch (final ClassCastException ex) {

                 throw new IllegalArgumentException("No date time pattern for locale: " + locale);

             }

         }

         return pattern;

     }

     // ----------------------------------------------------------------------

     /**

      * <p>Helper class to hold multi-part Map keys</p>

      */

     private static class MultipartKey {

         private final Object[] keys;

         private int hashCode;

         /**

          * Constructs an instance of <code>MultipartKey</code> to hold the specified objects.

          * @param keys the set of objects that make up the key.  Each key may be null.

          */

         public MultipartKey(final Object... keys) {

             this.keys = keys;

         }

         /**

          * {@inheritDoc}

          */

         @Override

         public boolean equals(final Object obj) {

             // Eliminate the usual boilerplate because

             // this inner static class is only used in a generic ConcurrentHashMap

             // which will not compare against other Object types

             return Arrays.equals(keys, ((MultipartKey)obj).keys);

         }

         /**

          * {@inheritDoc}

          */

         @Override

         public int hashCode() {

             if(hashCode==0) {

                 int rc= 0;

                 for(final Object key : keys) {

                     if(key!=null) {

                         rc= rc*7 + key.hashCode();

                     }

                 }

                 hashCode= rc;

             }

             return hashCode;

         }

     }

 }