/*
 /*
 * SonarQube PHP Custom Rules Example
 * Copyright (C) 2016-2016 SonarSource SA
 * mailto:contact AT sonarsource DOT com
 *
 * This program 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 3 of the License, or (at your option) any later version.
 *
 * This program 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 program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
package org.sonar.samples.php.checks;


import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.sonar.check.Rule;
import org.sonar.check.Priority;
import org.sonar.php.tree.symbols.Scope;
import org.sonar.plugins.php.api.symbols.Symbol;
import org.sonar.plugins.php.api.tree.declaration.FunctionDeclarationTree;
import org.sonar.plugins.php.api.tree.declaration.FunctionTree;
import org.sonar.plugins.php.api.tree.expression.FunctionExpressionTree;
import org.sonar.plugins.php.api.tree.statement.BlockTree;
import org.sonar.plugins.php.api.tree.statement.StatementTree;
import org.sonar.plugins.php.api.visitors.PHPVisitorCheck;

/**
 * Example of implementation of a check by extending {@link PHPVisitorCheck}.
 * PHPVisitorCheck provides methods to visit nodes of the Abstract Syntax Tree
 * that represents the source code.
 * <p>
 * Those methods can be overridden to process information
 * related to node and issue can be created via the context that can be
 * accessed through {@link PHPVisitorCheck#context()}.
 */
@Rule(
  key = NullValueCheckRule.KEY,
  priority = Priority.MAJOR,
  name = "Parameters should be checked for NULL condition before use.",
  tags = {"convention"},
// Description can either be given in this annotation or through HTML name <ruleKey>.html located in package src/resources/org/sonar/l10n/php/rules/<repositoryKey>
  description = "<p>Parameters should be checked for NULL condition before use.</p>"
  )
public class NullValueCheckRule extends PHPVisitorCheck {

	public static final String KEY = "NullValueCheck";
	

  /**
   * Overriding script visiting each of the function to create an issue
   * each time a function parameter is not checked for null value before use.
   */

	
	  @Override
	  public void visitFunctionDeclaration(FunctionDeclarationTree tree) {
	    checkParameters(tree);
	    super.visitFunctionDeclaration(tree);
	  }

	  @Override
	  public void visitFunctionExpression(FunctionExpressionTree tree) {
		checkParameters(tree);
	    super.visitFunctionExpression(tree);
	  }
	  
	  private void checkParameters(FunctionTree tree) {
		  
		  Scope scope = context().symbolTable().getScopeFor(tree);		  
		  BlockTree blockTree = (BlockTree)tree.body();
		  int index_is_null = 0;
  		  int index_param = 0;
		  List<StatementTree> statementTree = blockTree.statements();
		       
		  if (scope != null) {			  
			  for(StatementTree st : statementTree) {				  
				  for (Symbol symbol : scope.getSymbols(Symbol.Kind.PARAMETER)) {					  
					  index_is_null = 0;
		        	  index_param = 0;
		        	  
		        	  if(st.toString().contains(symbol.name())) {

		        		  index_param = st.toString().indexOf(symbol.name());
		        		  String str = "is_null(" + symbol.name().toString() + ")";	
		        		  String str_null_check = symbol.name().toString() + " != null";	
		        		  String str_null_check2 = "!(" + symbol.name().toString() + " == null)";	
		        		  
		        		  Pattern p1 = Pattern.compile(Pattern.quote(str_null_check));
		        		  Pattern p = Pattern.compile(Pattern.quote(str));
		        		  Pattern p2 = Pattern.compile(Pattern.quote(str_null_check2));

		        		  Matcher matcher = p.matcher(st.toString());
		        		  Matcher matcher1 = p1.matcher(st.toString());
		        		  Matcher matcher2 = p2.matcher(st.toString());

		        		  while(matcher.find())
		        		  {
		        			  index_is_null = matcher.start();
		        		  }
		        		  
		        		  while(matcher1.find())
		        		  {
		        			  index_is_null = matcher1.start();
		        		  }
		        		  
		        		  while(matcher2.find())
		        		  {
		        			  index_is_null = matcher2.start();
		        		  }		        		  
		        		  
		        		  if(index_is_null == 0 || index_param == 0 || index_param < index_is_null) {
		        			  context().newIssue(this, tree, "Parameters should be checked for NULL condition before use.");				        	
		        		  }		        		
		        	  }			        
				  }
			  }
		  } 		    
	  }	  	  
}