////////////////////////////////////////////////////////////////////////////////

 // checkstyle: Checks Java source code for adherence to a set of rules.

 // Copyright (C) 2001-2014  Oliver Burn

 //

 // This library is free software; you can redistribute it and/or

 // modify it under the terms of the GNU Lesser General Public

 // License as published by the Free Software Foundation; either

 // version 2.1 of the License, or (at your option) any later version.

 //

 // This library is distributed in the hope that it will be useful,

 // but WITHOUT ANY WARRANTY; without even the implied warranty of

 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 // Lesser General Public License for more details.

 //

 // You should have received a copy of the GNU Lesser General Public

 // License along with this library; if not, write to the Free Software

 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 ////////////////////////////////////////////////////////////////////////////////

 package com.puppycrawl.tools.checkstyle.checks.coding;

 import com.google.common.collect.Sets;

 import com.puppycrawl.tools.checkstyle.api.Check;

 import com.puppycrawl.tools.checkstyle.api.DetailAST;

 import com.puppycrawl.tools.checkstyle.api.FullIdent;

 import com.puppycrawl.tools.checkstyle.api.TokenTypes;

 import com.puppycrawl.tools.checkstyle.checks.CheckUtils;

 import java.util.Set;

 /**

  * <p>Checks that if a class defines a covariant method equals,

  * then it defines method equals(java.lang.Object).

  * Inspired by findbugs,

  * http://www.cs.umd.edu/~pugh/java/bugs/docs/findbugsPaper.pdf

  * </p>

  * <p>

  * An example of how to configure the check is:

  * </p>

  * <pre>

  * <module name="CovariantEquals"/>

  * </pre>

  * @author Rick Giles

  * @version 1.0

  */

 public class CovariantEqualsCheck extends Check

 {

     /** Set of equals method definitions */

     private final Set<DetailAST> mEqualsMethods = Sets.newHashSet();

     @Override

     public int[] getDefaultTokens()

     {

         return new int[] {TokenTypes.CLASS_DEF, TokenTypes.LITERAL_NEW, };

     }

     @Override

     public int[] getRequiredTokens()

     {

         return getDefaultTokens();

     }

     @Override

     public void visitToken(DetailAST aAST)

     {

         mEqualsMethods.clear();

         boolean hasEqualsObject = false;

         // examine method definitions for equals methods

         final DetailAST objBlock = aAST.findFirstToken(TokenTypes.OBJBLOCK);

         if (objBlock != null) {

             DetailAST child = objBlock.getFirstChild();

             while (child != null) {

                 if (child.getType() == TokenTypes.METHOD_DEF

                         && CheckUtils.isEqualsMethod(child))

                 {

                     if (hasObjectParameter(child)) {

                         hasEqualsObject = true;

                     }

                     else {

                         mEqualsMethods.add(child);

                     }

                 }

                 child = child.getNextSibling();

             }

             // report equals method definitions

             if (!hasEqualsObject) {

                 for (DetailAST equalsAST : mEqualsMethods) {

                     final DetailAST nameNode = equalsAST

                             .findFirstToken(TokenTypes.IDENT);

                     log(nameNode.getLineNo(), nameNode.getColumnNo(),

                             "covariant.equals");

                 }

             }

         }

     }

     /**

      * Tests whether a method definition AST has exactly one

      * parameter of type Object.

      * @param aAST the method definition AST to test.

      * Precondition: aAST is a TokenTypes.METHOD_DEF node.

      * @return true if aAST has exactly one parameter of type Object.

      */

     private boolean hasObjectParameter(DetailAST aAST)

     {

         // one parameter?

         final DetailAST paramsNode = aAST.findFirstToken(TokenTypes.PARAMETERS);

         if (paramsNode.getChildCount() != 1) {

             return false;

         }

         // parameter type "Object"?

         final DetailAST paramNode =

             paramsNode.findFirstToken(TokenTypes.PARAMETER_DEF);

         final DetailAST typeNode = paramNode.findFirstToken(TokenTypes.TYPE);

         final FullIdent fullIdent = FullIdent.createFullIdentBelow(typeNode);

         final String name = fullIdent.getText();

         return ("Object".equals(name) || "java.lang.Object".equals(name));

     }

 }