/*
 *  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.synapse.config.xml;

import org.apache.axiom.om.OMAttribute;
import org.apache.axiom.om.OMElement;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.synapse.SynapseConstants;
import org.apache.synapse.SynapseException;
import org.apache.synapse.message.processors.MessageProcessor;
import org.apache.synapse.util.xpath.SynapseXPath;
import org.jaxen.JaxenException;

import javax.xml.namespace.QName;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;


/**
 * Create an instance of the given Message processor, and sets properties on it.
 * <p/>
 * &lt;messageProcessor name="string" class="classname" messageStore = "string" &gt;
 * &lt;parameter name="string"&gt"string" &lt;parameter&gt;
 * &lt;parameter name="string"&gt"string" &lt;parameter&gt;
 * &lt;parameter name="string"&gt"string" &lt;parameter&gt;
 * .
 * .
 * &lt;/messageProcessor&gt;
 */
public class MessageProcessorFactory {
    private static final Log log = LogFactory.getLog(MessageProcessorFactory.class);
    public static final QName CLASS_Q = new QName(XMLConfigConstants.NULL_NAMESPACE, "class");
    public static final QName NAME_Q = new QName(XMLConfigConstants.NULL_NAMESPACE, "name");
    public static final QName EXPRESSION_Q = new QName(XMLConfigConstants.NULL_NAMESPACE, "expression");
    public static final QName PARAMETER_Q = new QName(XMLConfigConstants.SYNAPSE_NAMESPACE,
                                                      "parameter");
    public static final QName MESSAGE_STORE_Q = new QName(XMLConfigConstants.NULL_NAMESPACE,
                                                          "messageStore");
    public static final QName TARGET_ENDPOINT_Q =
            new QName(XMLConfigConstants.NULL_NAMESPACE, "targetEndpoint");
    private static final QName DESCRIPTION_Q
            = new QName(SynapseConstants.SYNAPSE_NAMESPACE, "description");
    public static final String FORWARDING_PROCESSOR =
            "org.apache.synapse.message.processors.forward.ScheduledMessageForwardingProcessor";


    /**
     * Creates a Message processor instance from given xml configuration element
     *
     * @param elem OMElement of that contain the Message processor configuration
     * @return created message processor instance
     */
    public static MessageProcessor createMessageProcessor(OMElement elem) {
        MessageProcessor processor = null;
        OMAttribute clssAtt = elem.getAttribute(CLASS_Q);

        if (clssAtt != null) {
            try {
                Class cls = Class.forName(clssAtt.getAttributeValue());
                processor = (MessageProcessor) cls.newInstance();
            } catch (Exception e) {
                handleException("Error while creating Message processor " + e.getMessage());
            }
        } else {
            /**We throw Exception since there is not default processor*/
            handleException("Can't create Message processor without a provider class");
        }

        OMAttribute nameAtt = elem.getAttribute(NAME_Q);
        if (nameAtt != null) {
            assert processor != null;
            processor.setName(nameAtt.getAttributeValue());
        } else {
            handleException("Can't create Message processor without a name ");
        }

        if (FORWARDING_PROCESSOR.equals(clssAtt.getAttributeValue())) {
            OMAttribute targetEndpointAtt = elem.getAttribute(TARGET_ENDPOINT_Q);

            if (targetEndpointAtt != null) {
                assert processor != null;
                processor.setTargetEndpoint(targetEndpointAtt.getAttributeValue());
            } else {
                // This validation is commented due to backward compatibility
                // handleException("Can't create Message processor without a target endpoint ");
            }
        }

        OMAttribute storeAtt = elem.getAttribute(MESSAGE_STORE_Q);

        if (storeAtt != null) {
            assert processor != null;
            processor.setMessageStoreName(storeAtt.getAttributeValue());
        } else {
            handleException("Can't create message processor without a message store");
        }

        OMElement descriptionElem = elem.getFirstChildWithName(DESCRIPTION_Q);
        if (descriptionElem != null) {
            assert processor != null;
            processor.setDescription(descriptionElem.getText());
        }

        assert processor != null;
        processor.setParameters(getParameters(elem));

        return processor;
    }

    private static Map<String, Object> getParameters(OMElement elem) {
        Iterator params = elem.getChildrenWithName(PARAMETER_Q);
        Map<String, Object> parameters = new HashMap<String, Object>();

        while (params.hasNext()) {
            Object o = params.next();
            if (o instanceof OMElement) {
                OMElement prop = (OMElement) o;
                OMAttribute paramName = prop.getAttribute(NAME_Q);
                String paramValue = prop.getText();
                OMAttribute paramExpression = prop.getAttribute(EXPRESSION_Q);
                if (paramName != null) {
                    if (paramExpression != null) {
                        try {
                            SynapseXPath expression = SynapseXPathFactory.getSynapseXPath(prop, paramExpression.getAttributeValue());
                            parameters.put(paramName.getAttributeValue(), expression);
                        } catch (JaxenException e) {
                            handleException("Error while creating expression " + e.getMessage());
                        }
                    } else if (paramValue != null) {
                        parameters.put(paramName.getAttributeValue(), paramValue);
                    } else {
                        handleException("Invalid MessageStore parameter - Parameter must have a value or an expression ");
                    }
                } else {
                    handleException("Invalid MessageStore parameter - Parameter must have a name ");
                }
            }
        }
        return parameters;
    }

    private static void handleException(String msg) {
        log.error(msg);
        throw new SynapseException(msg);
    }
}