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/*
 * Copyright (C) 2017 Square, Inc.
 *
 * 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 retrofit2;

import android.annotation.TargetApi;
import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Optional;
import javax.annotation.Nullable;
import okhttp3.ResponseBody;
import org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement;

/**
 * A {@link Converter.Factory} which supports Java's {@link Optional} to wrap null values from
 * another converter.
 * 
 * This factory is installed by default on the JVM and Android API 24+. If you are using another
 * converter which tries to serialize all types, such as Moshi or Gson, the default installation
 * of this factory never gets a chance to run. To work around this, you can explicitly install this
 * factory before your serialization library converter.
 */
@IgnoreJRERequirement // Only added when Optional is available (Java 8+ / Android API 24+).
@TargetApi(24)
public final class OptionalConverterFactory extends Converter.Factory {
  public static OptionalConverterFactory create() {
    return new OptionalConverterFactory();
  }

  OptionalConverterFactory() {}

  @Override
  public @Nullable Converter responseBodyConverter(
      Type type, Annotation[] annotations, Retrofit retrofit) {
    if (getRawType(type) != Optional.class) {
      return null;
    }

    Type innerType = getParameterUpperBound(0, (ParameterizedType) type);
    Converter delegate =
        retrofit.responseBodyConverter(innerType, annotations);
    return new OptionalConverter<>(delegate);
  }

  @IgnoreJRERequirement
  static final class OptionalConverter implements Converter> {
    private final Converter delegate;

    OptionalConverter(Converter delegate) {
      this.delegate = delegate;
    }

    @Override
    public Optional convert(ResponseBody value) throws IOException {
      return Optional.ofNullable(delegate.convert(value));
    }
  }
}