////////////////////////////////////////////////////////////////////////////////
   // checkstyle: Checks Java source code for adherence to a set of rules.
   // Copyright (C) 2001-2015 the original author or authors.
   //
   // 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 antlr.collections.AST;
  import com.puppycrawl.tools.checkstyle.api.Check;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  
  
  /**
   * <p>
   * Checks for overly complicated boolean return statements.
   * Idea shamelessly stolen from the equivalent PMD rule (pmd.sourceforge.net).
   * </p>
   * <p>
   * An example of how to configure the check is:
   * </p>
   * <pre>
   * &lt;module name="SimplifyBooleanReturn"/&gt;
   * </pre>
   * @author Lars Kühne
   */
  public class SimplifyBooleanReturnCheck
      extends Check
  {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_KEY = "simplify.boolreturn";
  
      @Override
      public int[] getDefaultTokens()
      {
          return new int[] {TokenTypes.LITERAL_IF};
      }
  
      @Override
      public int[] getAcceptableTokens()
      {
          return new int[] {TokenTypes.LITERAL_IF};
      }
  
      @Override
      public void visitToken(DetailAST ast)
      {
          // LITERAL_IF has the following four or five children:
          // '('
          // condition
          // ')'
          // thenStatement
          // [ LITERAL_ELSE (with the elseStatement as a child) ]
  
          // don't bother if this is not if then else
          final AST elseLiteral =
              ast.findFirstToken(TokenTypes.LITERAL_ELSE);
          if (elseLiteral == null) {
              return;
          }
          final AST elseStatement = elseLiteral.getFirstChild();
  
          // skip '(' and ')'
          // TODO: Introduce helpers in DetailAST
          final AST condition = ast.getFirstChild().getNextSibling();
          final AST thenStatement = condition.getNextSibling().getNextSibling();
  
          if (returnsOnlyBooleanLiteral(thenStatement)
              && returnsOnlyBooleanLiteral(elseStatement))
          {
              log(ast.getLineNo(), ast.getColumnNo(), MSG_KEY);
          }
      }
  
      /**
       * Returns if an AST is a return statment with a boolean literal
       * or a compound statement that contains only such a return statement.
       *
       * Returns <code>true</code> iff ast represents
       * <br/>
       * <pre>
      * return true/false;
      * </pre>
      * or
      * <br/>
      * <pre>
      * {
      *   return true/false;
      * }
      * </pre>
      *
      * @param ast the sytax tree to check
      * @return if ast is a return statment with a boolean literal.
      */
     private static boolean returnsOnlyBooleanLiteral(AST ast)
     {
         if (isBooleanLiteralReturnStatement(ast)) {
             return true;
         }
 
         final AST firstStmnt = ast.getFirstChild();
         return isBooleanLiteralReturnStatement(firstStmnt);
     }
 
     /**
      * Returns if an AST is a return statment with a boolean literal.
      *
      * Returns <code>true</code> iff ast represents
      * <br/>
      * <pre>
      * return true/false;
      * </pre>
      *
      * @param ast the sytax tree to check
      * @return if ast is a return statment with a boolean literal.
      */
     private static boolean isBooleanLiteralReturnStatement(AST ast)
     {
         if ((ast == null) || (ast.getType() != TokenTypes.LITERAL_RETURN)) {
             return false;
         }
 
         final AST expr = ast.getFirstChild();
 
         if ((expr == null) || (expr.getType() == TokenTypes.SEMI)) {
             return false;
         }
 
         final AST value = expr.getFirstChild();
         return isBooleanLiteralType(value.getType());
     }
 
     /**
      * Checks if a token type is a literal true or false.
      * @param tokenType the TokenType
      * @return true iff tokenType is LITERAL_TRUE or LITERAL_FALSE
      */
     private static boolean isBooleanLiteralType(final int tokenType)
     {
         final boolean iastrue = (tokenType == TokenTypes.LITERAL_TRUE);
         final boolean isFalse = (tokenType == TokenTypes.LITERAL_FALSE);
         return iastrue || isFalse;
     }
 }