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/*
 * Copyright 2011 the original author or 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 org.opencredo.couchdb;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.core.convert.ConversionService;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.expression.spel.support.StandardTypeConverter;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.integration.Message;
import org.springframework.integration.handler.AbstractMessageHandler;
import org.springframework.util.Assert;
import org.springframework.web.client.RestTemplate;

/**
 * A message handler that creates new CouchDB documents from SI messages.
 * The id of the created documents is by default that of the Spring Integration message, but this can be customized using a Spel expression.
 * This handler relies on a RestTemplate to communicate with CouchDB. By default a plain RestTemplate
 * is created but a custom one can be provided using the appropriate constructor.
 *
 * @author Tareq Abedrabbo ([email protected])
 * @since 11/01/2011
 */
public class CouchDbSendingMessageHandler extends AbstractMessageHandler {

    protected transient final Logger logger = LoggerFactory.getLogger(this.getClass());

    private static final ExpressionParser expressionParser = new SpelExpressionParser();

    private final RestTemplate restTemplate;
    private final String databaseUrl;
    private final StandardEvaluationContext evaluationContext = new StandardEvaluationContext();
    private Expression documentIdExpression;


    /**
     * Creates a handler instance with a database URL and a RestTemplate
     */
    public CouchDbSendingMessageHandler(String databaseUrl, RestTemplate restTemplate) {
        Assert.hasText(databaseUrl, "databaseUrl cannot be empty");
        Assert.notNull(restTemplate, "restTemplate cannot be null");
        this.databaseUrl = CouchDbUtils.addId(databaseUrl);
        this.restTemplate = restTemplate;
    }

    /**
     * Creates a handler instance with the database URL 
     */
    public CouchDbSendingMessageHandler(String databaseUrl) {
        this(databaseUrl, new RestTemplate());
    }


    @Override
    protected void onInit() {
        BeanFactory beanFactory = this.getBeanFactory();
        if (beanFactory != null) {
            this.evaluationContext.setBeanResolver(new BeanFactoryResolver(beanFactory));
        }
        ConversionService conversionService = this.getConversionService();
        if (conversionService != null) {
            this.evaluationContext.setTypeConverter(new StandardTypeConverter(conversionService));
        }
    }


    @Override
    protected final void handleMessageInternal(Message message) throws Exception {
        String documentId = createDocumentId(message);
        HttpEntity httpEntity = createHttpEntity(message);
        restTemplate.put(databaseUrl, httpEntity, documentId);
    }

    private HttpEntity createHttpEntity(Message message) {
        Object payload = message.getPayload();

        if (payload instanceof HttpEntity) {
            HttpEntity httpEntity = (HttpEntity) payload;
            Assert.isTrue(httpEntity.getHeaders().getContentType().equals(MediaType.APPLICATION_JSON),
                    "HttpEntity payload with non application/json content type found.");
            return httpEntity;
        }

        HttpHeaders httpHeaders = new HttpHeaders();
        httpHeaders.setContentType(MediaType.APPLICATION_JSON);
        HttpEntity