/*
 * 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 myservice.mynamespace.service;

import java.io.InputStream;
import java.util.List;
import java.util.Locale;

import myservice.mynamespace.data.Storage;

import org.apache.olingo.commons.api.data.ContextURL;
import org.apache.olingo.commons.api.data.Entity;
import org.apache.olingo.commons.api.edm.EdmEntitySet;
import org.apache.olingo.commons.api.edm.EdmEntityType;
import org.apache.olingo.commons.api.format.ContentType;
import org.apache.olingo.commons.api.http.HttpHeader;
import org.apache.olingo.commons.api.http.HttpStatusCode;
import org.apache.olingo.server.api.OData;
import org.apache.olingo.server.api.ODataApplicationException;
import org.apache.olingo.server.api.ODataRequest;
import org.apache.olingo.server.api.ODataResponse;
import org.apache.olingo.server.api.ServiceMetadata;
import org.apache.olingo.server.api.deserializer.DeserializerException;
import org.apache.olingo.server.api.processor.EntityProcessor;
import org.apache.olingo.server.api.serializer.EntitySerializerOptions;
import org.apache.olingo.server.api.serializer.ODataSerializer;
import org.apache.olingo.server.api.serializer.SerializerException;
import org.apache.olingo.server.api.serializer.SerializerResult;
import org.apache.olingo.server.api.uri.UriInfo;
import org.apache.olingo.server.api.uri.UriParameter;
import org.apache.olingo.server.api.uri.UriResource;
import org.apache.olingo.server.api.uri.UriResourceEntitySet;

public class DemoEntityProcessor implements EntityProcessor {


	private OData odata;
	private ServiceMetadata serviceMetadata;
	private Storage storage;



	public DemoEntityProcessor(Storage storage) {
		this.storage = storage;
	}


	public void init(OData odata, ServiceMetadata serviceMetadata) {
		this.odata = odata;
		this.serviceMetadata = serviceMetadata;
	}


	public void readEntity(ODataRequest request, ODataResponse response, UriInfo uriInfo, ContentType responseFormat)
							throws ODataApplicationException, SerializerException {

		// 1. retrieve the Entity Type
		List<UriResource> resourcePaths = uriInfo.getUriResourceParts();
		// Note: only in our example we can assume that the first segment is the EntitySet
		UriResourceEntitySet uriResourceEntitySet = (UriResourceEntitySet) resourcePaths.get(0);
		EdmEntitySet edmEntitySet = uriResourceEntitySet.getEntitySet();

		// 2. retrieve the data from backend
		List<UriParameter> keyPredicates = uriResourceEntitySet.getKeyPredicates();
		Entity entity = storage.readEntityData(edmEntitySet, keyPredicates);

		// 3. serialize
		EdmEntityType entityType = edmEntitySet.getEntityType();

		ContextURL contextUrl = ContextURL.with().entitySet(edmEntitySet).suffix(ContextURL.Suffix.ENTITY).build();
	 	// expand and select currently not supported
		EntitySerializerOptions options = EntitySerializerOptions.with().contextURL(contextUrl).build();

		ODataSerializer serializer = this.odata.createSerializer(responseFormat);
		SerializerResult serializerResult = serializer.entity(serviceMetadata, entityType, entity, options);
		InputStream entityStream = serializerResult.getContent();

		//4. configure the response object
		response.setContent(entityStream);
		response.setStatusCode(HttpStatusCode.OK.getStatusCode());
		response.setHeader(HttpHeader.CONTENT_TYPE, responseFormat.toContentTypeString());
	}




	/*
	 * These processor methods are not handled in this tutorial
	 * */
	public void createEntity(ODataRequest request, ODataResponse response, UriInfo uriInfo, ContentType requestFormat, 
	    ContentType responseFormat) throws ODataApplicationException, DeserializerException, SerializerException {
		throw new ODataApplicationException("Not supported.", HttpStatusCode.NOT_IMPLEMENTED.getStatusCode(), Locale.ROOT);
	}


	public void updateEntity(ODataRequest request, ODataResponse response, UriInfo uriInfo, ContentType requestFormat, 
	    ContentType responseFormat) throws ODataApplicationException, DeserializerException, SerializerException {
		throw new ODataApplicationException("Not supported.", HttpStatusCode.NOT_IMPLEMENTED.getStatusCode(), Locale.ROOT);
	}


	public void deleteEntity(ODataRequest request, ODataResponse response, UriInfo uriInfo) 
	    throws ODataApplicationException {
		throw new ODataApplicationException("Not supported.", HttpStatusCode.NOT_IMPLEMENTED.getStatusCode(), Locale.ROOT);
	}
}
