/*
 * 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.resolve.ParametrizedTypeJavaType;
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.NewClassTree;
import org.sonar.plugins.java.api.tree.Tree;

import java.util.List;

@Rule(key = "S2141")
public class ClassWithoutHashCodeInHashStructureCheck extends IssuableSubscriptionVisitor {

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

  @Override
  public void visitNode(Tree tree) {
    if (!hasSemantic()) {
      return;
    }
    Type type = ((NewClassTree) tree).symbolType();
    if (type instanceof ParametrizedTypeJavaType && useHashDataStructure(type)) {
      ParametrizedTypeJavaType ptt = (ParametrizedTypeJavaType) type;
      Symbol.TypeSymbol symbol = ptt.substitution(ptt.typeParameters().get(0)).symbol();
      if (implementsEquals(symbol) && !implementsHashCode(symbol)) {
        reportIssue(tree, "Add a \"hashCode()\" method to \"" + symbol.name() + "\" or remove it from this hash.");
      }
    }
  }

  private static boolean useHashDataStructure(Type type) {
    return type.isSubtypeOf("java.util.HashMap") || type.isSubtypeOf("java.util.HashSet") || type.isSubtypeOf("java.util.Hashtable");
  }

  private static boolean implementsEquals(Symbol.TypeSymbol symbol) {
    for (Symbol equals : symbol.lookupSymbols("equals")) {
      if (equals.isMethodSymbol()) {
        List<Type> params = ((Symbol.MethodSymbol) equals).parameterTypes();
        if (params.size() == 1 && params.get(0).is("java.lang.Object")) {
          return true;
        }
      }
    }
    return false;
  }

  private static boolean implementsHashCode(Symbol.TypeSymbol symbol) {
    for (Symbol hashCode : symbol.lookupSymbols("hashCode")) {
      if (hashCode.isMethodSymbol() && ((Symbol.MethodSymbol) hashCode).parameterTypes().isEmpty()) {
        return true;
      }
    }
    return false;
  }
}