/*

  * Copyright 2011-2013 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.pmd.rules.strings;

 import java.nio.ByteBuffer;

 import java.nio.CharBuffer;

 import java.nio.charset.CharacterCodingException;

 import java.nio.charset.Charset;

 import java.nio.charset.CharsetDecoder;

 import net.sourceforge.pmd.AbstractJavaRule;

 import net.sourceforge.pmd.PropertyDescriptor;

 import net.sourceforge.pmd.ast.ASTLiteral;

 import net.sourceforge.pmd.properties.StringProperty;

 /**

  * Rule to detect usage of characters of disallowed encoding in String literals.

  */

 public class StringLiteralEncodingRule extends AbstractJavaRule

 {

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

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

   /**

    * The descriptor to the {@link #encoding} property of this rule.

    */

   private static final PropertyDescriptor ENCODING_DESCRIPTOR =

       new StringProperty("encoding",

           "The name of the allowed encoding for string literals.", "US-ASCII",

           1.0f);

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

   /**

    * The allowed encoding.

    */

   private String encoding;

   /**

    * The decoder dependent on the {@link #encoding}.

    */

   private CharsetDecoder decoder;

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

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

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

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

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

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

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

   /**

    * Checks that there are disallowed encoded characters in String literals.

    * {@inheritDoc}

    *

    * @see net.sourceforge.pmd.AbstractJavaRule#visit(net.sourceforge.pmd.ast.ASTLiteral,

    *      java.lang.Object)

    */

   @Override

   public Object visit(final ASTLiteral node, final Object data)

   {

     provideRuleProperties();

     if (node.isStringLiteral())

     {

       final String literal = node.getImage();

       if (!isProperlyEncoded(literal))

       {

         final String message = createMessage(literal);

         addViolationWithMessage(data, node, message);

       }

     }

     return super.visit(node, data);

   }

   private String createMessage(final String literal)

   {

     return "String literal '" + literal + "' is not encoded with '" + encoding

            + "'.";

   }

   private void provideRuleProperties()

   {

     if (encoding == null)

     {

       encoding = getStringProperty(ENCODING_DESCRIPTOR);

       decoder = Charset.forName(encoding).newDecoder();

     }

   }

   /**

    * Inspired by <a href=

    * "http://stackoverflow.com/questions/3585053/in-java-is-it-possible-to-check-if-a-string-is-only-ascii"

    * >In Java, is it possible to check if a String is only ASCII?</a>.

    */

   private boolean isProperlyEncoded(final String string)

   {

     final byte[] stringBytes = string.getBytes();

     try

     {

       final CharBuffer buffer = decoder.decode(ByteBuffer.wrap(stringBytes));

       buffer.toString();

     }

     catch (final CharacterCodingException e)

     {

       return false;

     }

     return true;

   }

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

   /**

    * Returns the string representation of the class for debugging.

    *

    * @return the string representation of the class for debugging.

    */

   @Override

   public String toString()

   {

     return "StringLiteralEncodingRule with encoding '" + encoding + "'.";

   }

 }