/*
 * SonarQube Java
 * Copyright (C) 2012-2016 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.java.checks;

import com.google.common.collect.ImmutableList;

import org.sonar.check.Rule;
import org.sonar.java.model.ModifiersUtils;
import org.sonar.plugins.java.api.IssuableSubscriptionVisitor;
import org.sonar.plugins.java.api.semantic.Symbol;
import org.sonar.plugins.java.api.semantic.Type;
import org.sonar.plugins.java.api.tree.ClassTree;
import org.sonar.plugins.java.api.tree.Modifier;
import org.sonar.plugins.java.api.tree.Tree;
import org.sonar.plugins.java.api.tree.Tree.Kind;
import org.sonar.plugins.java.api.tree.TypeTree;
import org.sonar.plugins.java.api.tree.VariableTree;

import java.util.List;

@Rule(key = "S2160")
public class EqualsNotOverriddenInSubclassCheck extends IssuableSubscriptionVisitor {

  @Override
  public List<Kind> nodesToVisit() {
    return ImmutableList.of(Kind.CLASS);
  }

  @Override
  public void visitNode(Tree tree) {
    ClassTree classTree = (ClassTree) tree;
    if (hasSemantic() && shouldImplementEquals(classTree)) {
      reportIssue(classTree.simpleName(), "Override this superclass' \"equals\" method.");
    }
  }

  private static boolean shouldImplementEquals(ClassTree classTree) {
    return hasAtLeastOneField(classTree) && !implementsEquals(classTree) && parentClassImplementsEquals(classTree);
  }

  private static boolean hasAtLeastOneField(ClassTree classTree) {
    for (Tree member : classTree.members()) {
      if (isField(member)) {
        return true;
      }
    }
    return false;
  }

  private static boolean isField(Tree tree) {
    return tree.is(Kind.VARIABLE) && !ModifiersUtils.hasModifier(((VariableTree) tree).modifiers(), Modifier.STATIC);
  }

  private static boolean implementsEquals(ClassTree classTree) {
    return hasNotFinalEqualsMethod(classTree.symbol());
  }

  private static boolean parentClassImplementsEquals(ClassTree tree) {
    TypeTree superClass = tree.superClass();
    if (superClass != null) {
      Type superClassType = superClass.symbolType();
      while (superClassType.symbol().isTypeSymbol() && !superClassType.is("java.lang.Object")) {
        Symbol.TypeSymbol superClassSymbol = superClassType.symbol();
        if (hasNotFinalEqualsMethod(superClassSymbol)) {
          return true;
        }
        superClassType = superClassSymbol.superClass();
      }
    }
    return false;
  }

  private static boolean hasNotFinalEqualsMethod(Symbol.TypeSymbol superClassSymbol) {
    for (Symbol symbol : superClassSymbol.lookupSymbols("equals")) {
      if (isEqualsMethod(symbol) && !symbol.isFinal()) {
        return true;
      }
    }
    return false;
  }

  private static boolean isEqualsMethod(Symbol symbol) {
    if (symbol.isMethodSymbol()) {
      List<Type> parameterTypes = ((Symbol.MethodSymbol) symbol).parameterTypes();
      return !parameterTypes.isEmpty() && parameterTypes.get(0).is("java.lang.Object");
    }
    return false;
  }
}