/*

  * 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.shindig.social.opensocial.service;

 import org.apache.shindig.common.util.ImmediateFuture;

 import org.apache.shindig.social.ResponseError;

 import org.apache.shindig.social.opensocial.spi.SocialSpiException;

 import com.google.common.collect.ImmutableSet;

 import java.util.Collection;

 import java.util.Set;

 import java.util.concurrent.Future;

 public abstract class DataRequestHandler {

   private static final Set<String> GET_SYNONYMS = ImmutableSet.of("get");

   private static final Set<String> CREATE_SYNONYMS = ImmutableSet.of("put", "create");

   private static final Set<String> UPDATE_SYNONYMS = ImmutableSet.of("post", "update");

   private static final Set<String> DELETE_SYNONYMS = ImmutableSet.of("delete");

   public Future<?> handleItem(RequestItem request) {

     if (request.getOperation() == null) {

       return ImmediateFuture.errorInstance(new SocialSpiException(ResponseError.NOT_IMPLEMENTED,

           "Unserviced operation"));

     }

     String operation = request.getOperation().toLowerCase();

     Future<?> responseItem;

     try {

       if (GET_SYNONYMS.contains(operation)) {

         responseItem = handleGet(request);

       } else if (UPDATE_SYNONYMS.contains(operation)) {

         responseItem = handlePost(request);

       } else if (CREATE_SYNONYMS.contains(operation)) {

         responseItem = handlePut(request);

       } else if (DELETE_SYNONYMS.contains(operation)) {

         responseItem = handleDelete(request);

       } else {

         throw new SocialSpiException(ResponseError.NOT_IMPLEMENTED,

             "Unserviced operation " + operation);

       }

     } catch (SocialSpiException spe) {

       return ImmediateFuture.errorInstance(spe);

     } catch (Throwable t) {

       return ImmediateFuture.errorInstance(new SocialSpiException(ResponseError.INTERNAL_ERROR,

           "Unknown error " + t.getMessage(), t));

     }

     return responseItem;

   }

   protected abstract Future<?> handleDelete(RequestItem request)

       throws SocialSpiException;

   protected abstract Future<?> handlePut(RequestItem request)

       throws SocialSpiException;

   protected abstract Future<?> handlePost(RequestItem request)

       throws SocialSpiException;

   protected abstract Future<?> handleGet(RequestItem request)

       throws SocialSpiException;

   /**

    * Utility class for common API call preconditions

    */

   public static class Preconditions {

     public static void requireNotEmpty(Collection<?> coll, String message)

         throws SocialSpiException {

       if (coll.isEmpty()) {

         throw new SocialSpiException(ResponseError.BAD_REQUEST, message);

       }

     }

     public static void requireEmpty(Collection<?> list, String message) throws SocialSpiException {

       if (!list.isEmpty()) {

         throw new SocialSpiException(ResponseError.BAD_REQUEST, message);

       }

     }

     public static void requireSingular(Collection<?> coll, String message)

         throws SocialSpiException {

       if (coll.size() != 1) {

         throw new SocialSpiException(ResponseError.BAD_REQUEST, message);

       }

     }

     public static void requirePlural(Collection<?> coll, String message) throws SocialSpiException {

       if (coll.size() <= 1) {

         throw new SocialSpiException(ResponseError.BAD_REQUEST, message);

       }

     }

   }

 }