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/*
 * SonarQube Java
 * Copyright (C) 2012-2018 SonarSource SA
 * mailto:info 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.ImmutableMap;
import org.sonar.check.Rule;
import org.sonar.plugins.java.api.JavaFileScanner;
import org.sonar.plugins.java.api.JavaFileScannerContext;
import org.sonar.plugins.java.api.tree.BaseTreeVisitor;
import org.sonar.plugins.java.api.tree.IdentifierTree;
import org.sonar.plugins.java.api.tree.MemberSelectExpressionTree;
import org.sonar.plugins.java.api.tree.Tree.Kind;

import java.util.Map;

@Rule(key = "S1596")
public class CollectionsEmptyConstantsCheck extends BaseTreeVisitor implements JavaFileScanner {

  private static final Map IDENTIFIER_REPLACEMENT = new ImmutableMap.Builder()
    .put("EMPTY_LIST", "emptyList()")
    .put("EMPTY_MAP", "emptyMap()")
    .put("EMPTY_SET", "emptySet()")
    .build();

  private JavaFileScannerContext context;

  @Override
  public void scanFile(JavaFileScannerContext context) {
    this.context = context;
    scan(context.getTree());
  }

  @Override
  public void visitMemberSelectExpression(MemberSelectExpressionTree tree) {
    super.visitMemberSelectExpression(tree);
    String identifier = tree.identifier().name();
    boolean isCollectionsCall = tree.expression().is(Kind.IDENTIFIER) && "Collections".equals(((IdentifierTree) tree.expression()).name());
    boolean callEmptyConstant = identifier.startsWith("EMPTY_");
    if (isCollectionsCall && callEmptyConstant) {
      context.reportIssue(this, tree, "Replace \"Collections." + identifier + "\" by \"Collections." + IDENTIFIER_REPLACEMENT.get(identifier) + "\".");
    }
  }

}