/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.tajo.algebra;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import org.apache.tajo.algebra.CreateTable.PartitionMethodDescExpr;

public class JsonHelper {
  private static JsonHelper instance;

  private GsonBuilder builder;
  private Gson gson;

  static {
    instance = new JsonHelper();
  }

  private JsonHelper() {
    initBuilder();
    gson = builder.create();
  }

  private void initBuilder() {
    builder = new GsonBuilder().setPrettyPrinting().
        excludeFieldsWithoutExposeAnnotation();
    builder.registerTypeAdapter(OpType.class, new OpType.JsonSerDer());
    builder.registerTypeAdapter(Expr.class, new Expr.JsonSerDer());
    builder.registerTypeAdapter(PartitionMethodDescExpr.class, new PartitionMethodDescExpr.JsonSerDer());
  }


  public static Gson getInstance() {
    return instance.gson;
  }

  public static String toJson(Object obj) {
    return instance.gson.toJson(obj);
  }

  public static <T> T fromJson(String json, Class<T> clazz) {
    return instance.gson.fromJson(json, clazz);
  }
}