/**
 * Copyright 2012-2018 The Feign Authors
 *
 * Licensed 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 feign.gson;

import com.google.gson.Gson;
import com.google.gson.JsonIOException;
import com.google.gson.TypeAdapter;
import java.io.IOException;
import java.io.Reader;
import java.lang.reflect.Type;
import java.util.Collections;
import feign.Response;
import feign.Util;
import feign.codec.Decoder;
import static feign.Util.ensureClosed;

public class GsonDecoder implements Decoder {

  private final Gson gson;

  public GsonDecoder(Iterable<TypeAdapter<?>> adapters) {
    this(GsonFactory.create(adapters));
  }

  public GsonDecoder() {
    this(Collections.<TypeAdapter<?>>emptyList());
  }

  public GsonDecoder(Gson gson) {
    this.gson = gson;
  }

  @Override
  public Object decode(Response response, Type type) throws IOException {
    if (response.status() == 404)
      return Util.emptyValueOf(type);
    if (response.body() == null)
      return null;
    Reader reader = response.body().asReader();
    try {
      return gson.fromJson(reader, type);
    } catch (JsonIOException e) {
      if (e.getCause() != null && e.getCause() instanceof IOException) {
        throw IOException.class.cast(e.getCause());
      }
      throw e;
    } finally {
      ensureClosed(reader);
    }
  }
}