/*
 * SonarQube JavaScript Plugin
 * Copyright (C) 2011-2016 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.javascript.checks;

import org.sonar.api.server.rule.RulesDefinition;
import org.sonar.check.Priority;
import org.sonar.check.Rule;
import org.sonar.plugins.javascript.api.tree.Tree;
import org.sonar.plugins.javascript.api.tree.Tree.Kind;
import org.sonar.plugins.javascript.api.tree.declaration.InitializedBindingElementTree;
import org.sonar.plugins.javascript.api.tree.expression.AssignmentExpressionTree;
import org.sonar.plugins.javascript.api.tree.expression.ExpressionTree;
import org.sonar.plugins.javascript.api.tree.expression.IdentifierTree;
import org.sonar.plugins.javascript.api.visitors.BaseTreeVisitor;
import org.sonar.squidbridge.annotations.SqaleConstantRemediation;
import org.sonar.squidbridge.annotations.SqaleSubCharacteristic;

@Rule(
  key = "S2138",
  name = "\"undefined\" should not be assigned",
  priority = Priority.CRITICAL,
  tags = {Tags.PITFALL})
@SqaleSubCharacteristic(RulesDefinition.SubCharacteristics.LOGIC_RELIABILITY)
@SqaleConstantRemediation("2min")
public class UndefinedAssignmentCheck extends BaseTreeVisitor {

  private static final String MESSAGE = "Use null instead.";

  @Override
  public void visitInitializedBindingElement(InitializedBindingElementTree tree) {
    if (isUndefined(tree.right())) {
      reportIssue(tree);
    }

    super.visitInitializedBindingElement(tree);
  }

  @Override
  public void visitAssignmentExpression(AssignmentExpressionTree tree) {
    if (tree.is(Kind.ASSIGNMENT) && isUndefined(tree.expression())) {
      reportIssue(tree);
    }

    super.visitAssignmentExpression(tree);
  }

  private static boolean isUndefined(ExpressionTree expression) {
    return expression.is(Kind.IDENTIFIER_REFERENCE) && "undefined".equals(((IdentifierTree) expression).name());
  }

  private void reportIssue(Tree tree) {
    getContext().addIssue(this, tree, MESSAGE);
  }
}
