/*

  * Copyright 2012-2013 smartics, Kronseder & Reiner GmbH

  *

  * 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 de.smartics.properties.spi.core.constraint.jsr303;

 import java.lang.annotation.Annotation;

 import java.util.StringTokenizer;

 import java.util.regex.Matcher;

 import java.util.regex.Pattern;

 /**

  * A helper class to make JSR-303 constraints human readable in the context of

  * smartics properties.

  */

 final class ConstraintPrettifier

 {

   // ********************************* Fields *********************************

   // --- constants ------------------------------------------------------------

   /**

    * The pattern to match constraints in their native, typical

    * {@link Annotation#toString()} representation.

    */

   private static final Pattern PATTERN = Pattern

       .compile("@([^(]+)\\(([^)]+)\\)");

   // --- members --------------------------------------------------------------

   /**

    * The annotation prettified by this instance.

    */

   private final Annotation annotation;

   /**

    * The prettified instance of the annotation.

    */

   private final String pretty;

   // ****************************** Initializer *******************************

   // ****************************** Constructors ******************************

   /**

    * Default constructor.

    *

    * @param annotation the annotation prettified by this instance.

    * @throws NullPointerException if {@code annotation} is <code>null</code>.

    */

   ConstraintPrettifier(final Annotation annotation) throws NullPointerException

   {

     this.pretty = prettify(annotation);

     this.annotation = annotation;

   }

   // ****************************** Inner Classes *****************************

   /**

    * A parameter token.

    */

   private static final class ParameterToken

   {

     /**

      * The name of the token.

      */

     private String name;

     /**

      * Flag to check if the token a name/value pair.

      */

     private boolean isNameValue;

     /**

      * The original token.

      */

     private String token;

     private boolean isRelevantParameter()

     {

       return !("message".equals(name) || "groups".equals(name) || "payload"

           .equals(name)) && !tokenIsEmptyArray();

     }

     private boolean tokenIsEmptyArray()

     {

       return token.endsWith("=[]");

     }

     private void append(final StringBuilder buffer)

     {

       buffer.append(' ').append(token.trim()).append(',');

     }

   }

   // ********************************* Methods ********************************

   // --- init -----------------------------------------------------------------

   // --- get&set --------------------------------------------------------------

   private static String prettify(final Annotation annotation)

     throws NullPointerException

   {

     final String plain = annotation.toString();

     final Matcher matcher = PATTERN.matcher(plain);

     if (matcher.matches())

     {

       final StringBuilder buffer = new StringBuilder(128);

       final String constraint = matcher.group(1);

       addConstraint(buffer, constraint);

       final String parameter = matcher.group(2);

       addParameter(buffer, parameter);

       return buffer.toString();

     }

     else

     {

       return plain;

     }

   }

   private static void addConstraint(final StringBuilder buffer,

       final String constraint)

   {

     final int index = constraint.lastIndexOf('.');

     if (index > -1 && index < constraint.length() - 1)

     {

       final String shortName = constraint.substring(index + 1);

       buffer.append(shortName);

     }

     else

     {

       buffer.append(constraint);

     }

   }

   private static void addParameter(final StringBuilder buffer,

       final String parameter)

   {

     final int initialLength = buffer.length();

     final StringTokenizer tokenizer = new StringTokenizer(parameter, ",");

     while (tokenizer.hasMoreTokens())

     {

       final ParameterToken token = fetchToken(tokenizer);

       if (token.isNameValue)

       {

         if (token.isRelevantParameter())

         {

           token.append(buffer);

         }

       }

       else

       {

         token.append(buffer);

       }

     }

     if (initialLength < buffer.length())

     {

       buffer.setCharAt(initialLength, '(');

       buffer.setCharAt(buffer.length() - 1, ')');

     }

   }

   private static ParameterToken fetchToken(final StringTokenizer tokenizer)

   {

     final ParameterToken result = new ParameterToken();

     String token = tokenizer.nextToken();

     final int index = token.indexOf('=');

     result.isNameValue = index != -1;

     if (result.isNameValue)

     {

       final StringBuilder buffer = new StringBuilder(24);

       if (token.charAt(index + 1) == '[')

       {

         while (tokenizer.hasMoreTokens() && !token.endsWith("]"))

         {

           buffer.append(token).append(',');

           token = tokenizer.nextToken();

         }

         buffer.append(token);

         result.token = buffer.toString();

       }

       else

       {

         result.token = token;

       }

       result.name = result.token.substring(0, index).trim();

     }

     return result;

   }

   /**

    * Returns the annotation prettified by this instance.

    *

    * @return the annotation prettified by this instance.

    */

   public Annotation getAnnotation()

   {

     return annotation;

   }

   /**

    * Returns the prettified instance of the annotation.

    *

    * @return the prettified instance of the annotation.

    */

   public String getPretty()

   {

     return pretty;

   }

   // --- business -------------------------------------------------------------

   // --- object basics --------------------------------------------------------

   @Override

   public String toString()

   {

     return pretty;

   }

 }