/*
 *  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 java.io.StringReader;
import org.apache.axiom.om.OMAbstractFactory;
import org.apache.axiom.om.OMComment;
import org.apache.axiom.om.OMElement;
import org.apache.axiom.om.OMFactory;
import org.apache.axiom.om.OMNamespace;
import org.apache.axiom.om.OMXMLBuilderFactory;
import org.apache.axiom.om.xpath.AXIOMXPath;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.synapse.Mediator;
import org.apache.synapse.SynapseConstants;
import org.apache.synapse.SynapseException;
import org.apache.synapse.aspects.AspectConfigurable;
import org.apache.synapse.aspects.statistics.StatisticsConfigurable;
import org.apache.synapse.mediators.MediatorProperty;
import org.apache.synapse.mediators.builtin.CommentMediator;

import javax.xml.namespace.QName;
import java.util.Collection;
import java.util.List;

/**
 * Parent class for all the {@link MediatorSerializer} implementations
 */
public abstract class AbstractMediatorSerializer implements MediatorSerializer {

    /** the standard log for mediators, will assign the logger for the actual subclass */
    protected static Log log;

    protected static final OMFactory fac = OMAbstractFactory.getOMFactory();
    protected static final OMNamespace synNS = SynapseConstants.SYNAPSE_OMNAMESPACE;
    protected static final OMNamespace nullNS
            = fac.createOMNamespace(XMLConfigConstants.NULL_NAMESPACE, "");
    protected static final QName PROP_Q
        = new QName(XMLConfigConstants.SYNAPSE_NAMESPACE, "property");
    protected static final QName DESCRIPTION_Q
        = new QName(XMLConfigConstants.SYNAPSE_NAMESPACE, "description");
    private static final String CUSTOM_MEDIATOR_START_TAG = "<CUSTOM_";
    /**
     * A constructor that makes subclasses pick up the correct logger
     */
    protected AbstractMediatorSerializer() {
        log = LogFactory.getLog(this.getClass());
    }

    /**
     * Serializes the given mediator into XML element. This method handles
     * adding the common information from the respective mediators to the element it get by
     * delegating the mediator specific serialization to the
     * {@link #serializeSpecificMediator(org.apache.synapse.Mediator)} method, which has tobe
     * implemented by the respective mediators</p>
     *
     * <p>It is treating the {@link org.apache.synapse.config.xml.AnonymousListMediator} as a
     * special case and calls it's children serialization, since there is nothing specific to be
     * serialized in that case</p>
     *
     * <p>This method has been marked as <code>final</code> to avoid mistakenly overwriting
     * this method instead of the {@link #serializeSpecificMediator(org.apache.synapse.Mediator)}
     * by the sub classes
     *
     * @param parent the OMElement to which the serialization should be attached
     * @param m mediator to be serialized
     * @return the serialized Element
     */
    public final OMElement serializeMediator(OMElement parent, Mediator m) {
        OMElement serializedElement = null;

        if (m instanceof AnonymousListMediator) {
            ((AnonymousListMediatorSerializer) this).serializeChildren(parent,
                                                                       ((AnonymousListMediator) m).getList());
            serializedElement = parent;
        } else if (m instanceof CommentMediator) {
            // serialize comment mediator
            serializedElement = serializeComments(parent, m);
        } else {
            // delegate the specific serializations to it's serializer
            OMElement elem = serializeSpecificMediator(m);
            if (m.getDescription() != null) {
                OMElement descriptionElem = fac.createOMElement(DESCRIPTION_Q, elem);
                descriptionElem.setText(m.getDescription());
                elem.addChild(descriptionElem);
            }
            if (m.getShortDescription() != null) {
                elem.addAttribute(
                        fac.createOMAttribute("description", nullNS, m.getShortDescription()));
            }

            // attach the serialized element to the parent
            if (parent != null) {
                parent.addChild(elem);
            }
            serializedElement = elem;
        }
        return serializedElement;

    }

    /**
     * Specific mediator factory implementations should implement this method to build the
     * {@link org.apache.synapse.Mediator} by the given XML configuration
     *
     * @param m mediator to be serialized
     * @return serialized element of the mediator
     */
    protected abstract OMElement serializeSpecificMediator(Mediator m);

    /**
     * Perform common functions and finalize the mediator serialization.
     * i.e. process any common attributes
     *
     * @param mediatorOmElement the OMElement being created
     * @param mediator the Mediator instance being serialized
     */
    protected static void saveTracingState(OMElement mediatorOmElement, Mediator mediator) {
        int traceState = mediator.getTraceState();
        String traceValue = null;
        if (traceState == org.apache.synapse.SynapseConstants.TRACING_ON) {
            traceValue = XMLConfigConstants.TRACE_ENABLE;
        } else if (traceState == org.apache.synapse.SynapseConstants.TRACING_OFF) {
            traceValue = XMLConfigConstants.TRACE_DISABLE;
        }
        if (traceValue != null) {
            mediatorOmElement.addAttribute(fac.createOMAttribute(
                XMLConfigConstants.TRACE_ATTRIB_NAME, nullNS, traceValue));
        }

        if (mediator instanceof AspectConfigurable) {
            StatisticsConfigurable statisticsConfigurable =
                    ((AspectConfigurable) mediator).getAspectConfiguration();

            if (statisticsConfigurable != null &&
                    statisticsConfigurable.isStatisticsEnable()) {

                mediatorOmElement.addAttribute(fac.createOMAttribute(
                        XMLConfigConstants.STATISTICS_ATTRIB_NAME, nullNS,
                        XMLConfigConstants.STATISTICS_ENABLE));
            }

            if (statisticsConfigurable != null &&
                statisticsConfigurable.isTracingEnabled()) {

                mediatorOmElement.addAttribute(fac.createOMAttribute(
                        XMLConfigConstants.TRACE_ATTRIB_NAME, nullNS,
                        XMLConfigConstants.TRACE_ENABLE));
            }
        }

    }

    protected void serializeMediatorProperties(OMElement parent,
                                               Collection<MediatorProperty> props,
                                               QName childElementName) {

        for (MediatorProperty mp : props) {
            OMElement prop = fac.createOMElement(childElementName, parent);
            if (mp.getName() != null) {
                prop.addAttribute(fac.createOMAttribute("name", nullNS, mp.getName()));
            } else {
                handleException("Mediator property name missing");
            }

            if (mp.getValue() != null) {
                prop.addAttribute(fac.createOMAttribute("value", nullNS, mp.getValue()));

            } else if (mp.getExpression() != null) {
                SynapsePathSerializer.serializePath(mp.getExpression(), prop, "expression");

            } else {
                handleException("Mediator property must have a literal value or be an expression");
            }
        }
    }
    
    protected void serializeMediatorProperties(OMElement parent,
            Collection<MediatorProperty> props) {
        
        serializeMediatorProperties(parent, props, PROP_Q);
    }

    protected void serializeProperties(OMElement parent, Collection<MediatorProperty> props) {
        serializeMediatorProperties(parent, props);
    }

    protected void serializeNamespaces(OMElement elem, AXIOMXPath xpath) {
        for (Object obj : xpath.getNamespaces().keySet()) {
            String prefix = (String) obj;
            String uri = xpath.getNamespaceContext().translateNamespacePrefixToUri(prefix);
            if (!XMLConfigConstants.SYNAPSE_NAMESPACE.equals(uri)) {
                elem.declareNamespace(uri, prefix);
            }
        }
    }

    protected void handleException(String msg) {
        LogFactory.getLog(this.getClass()).error(msg);
        throw new SynapseException(msg);
    }

    protected void handleException(String msg, Exception e) {
        LogFactory.getLog(this.getClass()).error(msg, e);
        throw new SynapseException(msg, e);
    }

    /**
     * Serialize String Comment entries from a List
     *
     * @param parent      OMElement to be updated
     * @param commentList List of comment entries to be serialized
     */
    protected void serializeComments(OMElement parent, List<String> commentList) {
        for (String comment : commentList) {
            OMComment commendNode = fac.createOMComment(parent, "comment");
            commendNode.setValue(comment);
            parent.addChild(commendNode);
        }
    }

    /**
     * Serialize String  Comment entries from a List
     *
     * @param parent OMElement to be updated
     * @param m      Comment mediator instance which contains comment information
     */
    protected OMElement serializeComments(OMElement parent, Mediator m) {
        String comment = ((CommentMediator) m).getCommentText();
        if (comment.startsWith(CUSTOM_MEDIATOR_START_TAG)) {
            StringReader xmlText = new StringReader(comment);
            OMElement elementNode = OMXMLBuilderFactory.createOMBuilder(xmlText).getDocumentElement();
            parent.addChild(elementNode);
            return parent;
        }
        OMComment commendNode = fac.createOMComment(parent, "comment");
        commendNode.setValue(((CommentMediator) m).getCommentText());
        parent.addChild(commendNode);
        return parent;
    }
}
