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/*
 * -\-\-
 * Spotify Apollo Extra
 * --
 * Copyright (C) 2013 - 2015 Spotify AB
 * --
 * 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 com.spotify.apollo.route;

import com.google.common.base.Throwables;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectWriter;
import com.spotify.apollo.Response;

import okio.ByteString;

public class JsonSerializerMiddlewares {
  private JsonSerializerMiddlewares() {
    // prevent instantiation
  }

  private static final String CONTENT_TYPE = "Content-Type";
  private static final String JSON = "application/json; charset=UTF8";

  private static  ByteString serialize(ObjectWriter objectWriter, T object) {
    try {
      return ByteString.of(objectWriter.writeValueAsBytes(object));
    } catch (JsonProcessingException e) {
      throw Throwables.propagate(e);
    }
  }

  private static  Response serialize(ObjectWriter objectWriter, Response response){
    if(!response.payload().isPresent()){
      // Same as in com.spotify.apollo.route.Middlewares.serializePayload()
      // no payload, so this cast is safe to do
      //noinspection unchecked
      return (Response) response;
    } else {
      return response.withPayload(serialize(objectWriter, response.payload().get()));
    }
  }

  /**
   * Middleware that serializes the result of the inner handler using the supplied
   * {@link ObjectWriter}, and sets the Content-Type header to application/json.
   */
  public static  Middleware, AsyncHandler>>
  jsonSerialize(ObjectWriter objectWriter) {
   return handler ->
       requestContext -> handler.invoke(requestContext)
           .thenApply(result -> Response
               .forPayload(serialize(objectWriter, result))
               .withHeader(CONTENT_TYPE, JSON));
  }

  /**
   * Middleware that serializes the payload of the result response of the inner handler using
   * the supplied {@link ObjectWriter}, and sets the Content-Type header to application/json.
   */
  public static  Middleware>, AsyncHandler>>
  jsonSerializeResponse(ObjectWriter objectWriter) {
   return handler ->
       requestContext -> handler.invoke(requestContext)
           .thenApply(response -> serialize(objectWriter, response)
               .withHeader(CONTENT_TYPE, JSON));
  }

  public static  Middleware, AsyncHandler>>
  jsonSerializeSync(ObjectWriter objectWriter) {
    Middleware, AsyncHandler> syncToAsync = Middleware::syncToAsync;
    return syncToAsync.and(jsonSerialize(objectWriter));
  }

  public static  Middleware>, AsyncHandler>>
  jsonSerializeResponseSync(ObjectWriter objectWriter) {
    Middleware>, AsyncHandler>> syncToAsync = Middleware::syncToAsync;
    return syncToAsync.and(jsonSerializeResponse(objectWriter));
  }
}