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/*
 * SonarQube Java
 * Copyright (C) 2012 SonarSource
 * [email protected]
 *
 * 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  02
 */
package org.sonar.java.checks;

import com.google.common.collect.ImmutableList;
import org.sonar.api.server.rule.RulesDefinition;
import org.sonar.check.Priority;
import org.sonar.check.Rule;
import org.sonar.java.tag.Tag;
import org.sonar.plugins.java.api.semantic.Symbol;
import org.sonar.plugins.java.api.semantic.Type;
import org.sonar.plugins.java.api.tree.BaseTreeVisitor;
import org.sonar.plugins.java.api.tree.BlockTree;
import org.sonar.plugins.java.api.tree.CatchTree;
import org.sonar.plugins.java.api.tree.MethodInvocationTree;
import org.sonar.plugins.java.api.tree.Tree;
import org.sonar.plugins.java.api.tree.Tree.Kind;
import org.sonar.plugins.java.api.tree.TryStatementTree;
import org.sonar.plugins.java.api.tree.TypeTree;
import org.sonar.plugins.java.api.tree.UnionTypeTree;
import org.sonar.squidbridge.annotations.SqaleConstantRemediation;
import org.sonar.squidbridge.annotations.SqaleSubCharacteristic;

import java.util.List;

@Rule(
  key = "S2221",
  name = "\"Exception\" should not be caught when not required by called methods",
  priority = Priority.CRITICAL,
  tags = {Tag.CWE, Tag.ERROR_HANDLING, Tag.SECURITY})
@SqaleSubCharacteristic(RulesDefinition.SubCharacteristics.EXCEPTION_HANDLING)
@SqaleConstantRemediation("15min")
public class CatchExceptionCheck extends SubscriptionBaseVisitor {

  private final ThrowsExceptionVisitor throwsExceptionVisitor = new ThrowsExceptionVisitor();

  @Override
  public List nodesToVisit() {
    return ImmutableList.of(Kind.TRY_STATEMENT);
  }

  @Override
  public void visitNode(Tree tree) {
    TryStatementTree tryStatement = (TryStatementTree) tree;
    for (CatchTree catchTree : tryStatement.catches()) {
      TypeTree catchType = catchTree.parameter().type();
      if (catchesException(catchType, tryStatement.block())) {
        addIssue(catchType, "Catch a list of specific exception subtypes instead.");
      }
    }
  }

  private boolean catchesException(TypeTree catchType, BlockTree block) {
    if (catchType.is(Kind.UNION_TYPE)) {
      UnionTypeTree unionTypeTree = (UnionTypeTree) catchType;
      for (TypeTree typeAlternative : unionTypeTree.typeAlternatives()) {
        if (catchesExceptionCheck(block, typeAlternative)) {
          return true;
        }
      }
    } else if (catchesExceptionCheck(block, catchType)) {
      return true;
    }
    return false;
  }

  private boolean catchesExceptionCheck(BlockTree block, TypeTree catchType) {
    return isJavaLangException(catchType.symbolType()) && !throwsExceptionVisitor.containsExplicitThrowsException(block);
  }

  private static boolean isJavaLangException(Type type) {
    return type.is("java.lang.Exception");
  }

  private static class ThrowsExceptionVisitor extends BaseTreeVisitor {
    private boolean containsExplicitThrowsException;

    boolean containsExplicitThrowsException(Tree tree) {
      containsExplicitThrowsException = false;
      tree.accept(this);
      return containsExplicitThrowsException;
    }

    @Override
    public void visitMethodInvocation(MethodInvocationTree tree) {
      if (containsExplicitThrowsException) {
        return;
      }
      Symbol symbol = tree.symbol();
      if (symbol.isMethodSymbol()) {
        for (Type type : ((Symbol.MethodSymbol) symbol).thrownTypes()) {
          if (isJavaLangException(type)) {
            containsExplicitThrowsException = true;
            return;
          }
        }
      }
      super.visitMethodInvocation(tree);
    }
  }

}