/*
 * Copyright 1999-2004 The Apache Software Foundation.
 * 
 * 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.apache.cocoon.components.source.impl;


import java.io.InputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.ByteArrayOutputStream;
import java.io.ByteArrayInputStream;
import java.net.MalformedURLException;
import java.util.Map;

import org.apache.avalon.framework.configuration.ConfigurationException;
import org.apache.avalon.framework.logger.Logger;
import org.apache.avalon.framework.service.ServiceException;
import org.apache.avalon.framework.service.ServiceManager;
import org.apache.avalon.framework.service.ServiceSelector;

import org.apache.excalibur.source.ModifiableSource;
import org.apache.excalibur.source.SourceException;
import org.apache.excalibur.source.impl.AbstractSource;
import org.apache.excalibur.xml.sax.SAXParser;
import org.apache.excalibur.xml.sax.XMLizable;

import org.apache.cocoon.components.modules.input.InputModule;
import org.apache.cocoon.components.modules.output.OutputModule;
import org.apache.cocoon.serialization.XMLSerializer;
import org.apache.cocoon.util.jxpath.DOMFactory;
import org.apache.cocoon.xml.dom.DOMBuilder;
import org.apache.cocoon.xml.dom.DOMStreamer;

import org.apache.commons.jxpath.JXPathContext;

import org.w3c.dom.Document;
import org.w3c.dom.Node;

import org.xml.sax.ContentHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

/**
 * A <code>ModifiableSource</code> that takes its content from a
 * module.
 * <p>The URI syntax is
 * "xmodule:[<input-module>|<output-module>]:attribute-name[#XPath]",
 * where :
 * <ul>
 * <li>an input-module name is used for finding an input-module for reading data from</li>,
 * <li>an output-module name is used for finding an output-module for writing data to</li>,
 * <li>"attribute-name" is the name of the attribute found in the module</li>,
 * <li>"XPath" is an XPath that is aplied on the object in the
 * attribute, by using JXPath.</li>
 * </ul>
 * </p>
 *
 * @author <a href="mailto:danielf@nada.kth.se">Daniel Fagerstom</a>
 */

public class XModuleSource
    extends AbstractSource
    implements ModifiableSource, XMLizable, DOMBuilder.Listener {

    private final static String SCHEME = "xmodule";
    private String attributeType;
    private String attributeName;
    private String xPath;
    private ServiceManager manager;
    private Map objectModel;
    private Logger logger;
    
    /**
     * Create a xmodule source from a 'xmodule:' uri and a the object model.
     * <p>The uri is of the form "xmodule:/attribute-type/attribute-name/xpath</p>
     */
    public XModuleSource( Map objectModel, String uri,
                          ServiceManager manager, Logger logger )
        throws MalformedURLException, SourceException {

        this.objectModel = objectModel;
        this.manager = manager;
        this.logger = logger;

        setSystemId( uri );

        // Scheme
        int start = 0;
        int end = uri.indexOf( ':' );
        if ( end == -1 )
            throw new MalformedURLException("Malformed uri for xmodule source (cannot find scheme) : " + uri);

        String scheme = uri.substring( start, end );
        if ( !SCHEME.equals( scheme ) )
            throw new MalformedURLException("Malformed uri for a xmodule source : " + uri);

        setScheme( scheme );

        // Attribute type
        start = end + 1;
        end = uri.indexOf( ':', start );
        if ( end == -1 ) {
            throw new MalformedURLException("Malformed uri for xmodule source (cannot find attribute type) : " + uri);
        }
        this.attributeType = uri.substring( start, end );

        // Attribute name
        start = end + 1;
        end = uri.indexOf( '#', start );

        if ( end == -1 )
            end = uri.length();

        if ( end == start )
            throw new MalformedURLException("Malformed uri for xmodule source (cannot find attribute name) : " + uri);

        this.attributeName = uri.substring( start, end );

        // xpath
        start = end + 1;
        this.xPath = start < uri.length() ? uri.substring( start ) : "";
    }
    
    /**
     * Implement this method to obtain SAX events.
     *
     */

    public void toSAX(ContentHandler handler)
        throws SAXException {

        Object obj = getInputAttribute( this.attributeType, this.attributeName );
        if ( obj == null )
            throw new SAXException( " The attribute: " + this.attributeName +
                                    " is empty" );

        if ( !(this.xPath.length() == 0 || this.xPath.equals( "/" )) ) {
            JXPathContext context = JXPathContext.newContext( obj );

            obj = context.getPointer( this.xPath ).getNode();

            if ( obj == null )
                throw new SAXException( "the xpath: " + this.xPath +
                                        " applied on the attribute: " +
                                        this.attributeName +
                                        " returns null");
        }

        if ( obj instanceof Document ) {
            DOMStreamer domStreamer = new DOMStreamer( handler );
            domStreamer.stream( (Document)obj );
        } else if ( obj instanceof Node ) {
            DOMStreamer domStreamer = new DOMStreamer( handler );
            handler.startDocument();
            domStreamer.stream( (Node)obj );
            handler.endDocument();
        } else if ( obj instanceof XMLizable ) {
            ((XMLizable)obj).toSAX( handler );
        } else {
            throw new SAXException( "The object type: " + obj.getClass() +
                                    " could not be serialized to XML: " + obj );
        }
    }

    /**
     * Return an <code>InputStream</code> object to read from the source.
     *
     * @throws IOException if I/O error occured.
     */
    // Stolen from QDoxSource
    public InputStream getInputStream() throws IOException, SourceException {
        if ( this.logger.isDebugEnabled() ) {
            this.logger.debug( "Getting InputStream for " + getURI() );
        }

        // Serialize the SAX events to the XMLSerializer:

        XMLSerializer serializer = new XMLSerializer();
        ByteArrayInputStream inputStream = null;

        try {
            ByteArrayOutputStream outputStream = new ByteArrayOutputStream( 2048 );
            serializer.setOutputStream( outputStream );
            toSAX( serializer );
            inputStream = new ByteArrayInputStream( outputStream.toByteArray() );
        } catch ( SAXException se ) {
            logger.error( "SAX exception!", se );
            throw new SourceException( "Serializing SAX to a ByteArray failed!", se );
        }

        return inputStream;
    }

    /**
     * Does this source actually exist ?
     *
     * @return true if the resource exists.
     *
     */
    public boolean exists() {
        boolean exists = false;
        try {
            exists = getInputAttribute( this.attributeType, this.attributeName ) != null;
        } catch ( SAXException e ) {
            exists = false;
        }
        return exists;
    }

    /**
     * Get an <code>InputStream</code> where raw bytes can be written to.
     * The signification of these bytes is implementation-dependent and
     * is not restricted to a serialized XML document.
     *
     * @return a stream to write to
     */ 
    public OutputStream getOutputStream() throws IOException {
        return new DOMOutputStream();
    }

    /**
     * Delete the source 
     */
    public void delete() throws SourceException {
        if ( !(this.xPath.length() == 0 || this.xPath.equals( "/" )) ) {
            Object value;
            try {
                value = getInputAttribute( this.attributeType, this.attributeName );
            } catch ( SAXException e ) {
                throw new SourceException( "delete: ", e );
            }
            if ( value == null )
                throw new SourceException( " The attribute: " + this.attributeName +
                                           " is empty" );

            JXPathContext context = JXPathContext.newContext( value );
            context.removeAll( this.xPath );
        } else {
            try {
                setOutputAttribute( this.attributeType, this.attributeName, null );
            } catch ( SAXException e ) {
                throw new SourceException( "delete: ", e );
            }
        }
    }

    /**
     * FIXME
     * delete is an operator in java script, this method is for
     * testing puposes in java script only
     */
    public void deleteTest() throws SourceException {
        delete();
    }

    /**
     * Can the data sent to an <code>OutputStream</code> returned by
     * {@link #getOutputStream()} be cancelled ?
     *
     * @return true if the stream can be cancelled
     */
    public boolean canCancel( OutputStream stream ) { return false; }

    /**
     * Cancel the data sent to an <code>OutputStream</code> returned by
     * {@link #getOutputStream()}.
     * <p>
     * After cancel, the stream should no more be used.
     */
    public void cancel(OutputStream stream) throws IOException {}

    /**
     * Get a <code>ContentHandler</code> where an XML document can
     * be written using SAX events.
     * <p>
     * Care should be taken that the returned handler can actually
     * be a {@link org.apache.cocoon.xml.XMLConsumer} supporting also
     * lexical events such as comments.
     *
     * @return a handler for SAX events
     */
    public ContentHandler getContentHandler() {
        return new DOMBuilder( this );
    }

    public void notify( Document insertDoc ) throws SAXException {

        // handle xpaths, we are only handling inserts, i.e. if there is no
        // attribute of the given name and type the operation will fail
        if ( !(this.xPath.length() == 0 || this.xPath.equals( "/" )) ) {

            Object value = getInputAttribute( this.attributeType, this.attributeName );
            if ( value == null )
                throw new SAXException( " The attribute: " + this.attributeName +
                                        " is empty" );

            JXPathContext context = JXPathContext.newContext( value );

            if ( value instanceof Document ) {
                // If the attribute contains a dom document we
                // create the elements in the given xpath if
                // necesary, import the input document and put it
                // in the place described by the xpath.
                Document doc = (Document)value;
                
                Node importedNode =
                    doc.importNode( insertDoc.getDocumentElement(), true );
                
                context.setLenient( true );
                context.setFactory( new DOMFactory() );
                context.createPathAndSetValue( this.xPath, importedNode );
            } else {
                // Otherwise just try to put a the input document in
                // the place pointed to by the xpath
                context.setValue( this.xPath, insertDoc );
            }
                    
        } else {
            setOutputAttribute( this.attributeType, this.attributeName, insertDoc );
        }
    }

    private class DOMOutputStream extends ByteArrayOutputStream {
        public void close() throws IOException {
            SAXParser parser = null;
            try {
                parser = (SAXParser)XModuleSource.this.manager.lookup( SAXParser.ROLE );

                parser.parse( new InputSource( new ByteArrayInputStream( super.toByteArray() ) ),
                              XModuleSource.this.getContentHandler());
            } catch (Exception e){
                throw new IOException("Exception during processing of " +
                                       XModuleSource.super.getURI() +
                                       e.getMessage());
            } finally {
                if (parser != null) XModuleSource.this.manager.release( parser );
            }
            super.close();
        }
    }


    private Object getInputAttribute( String inputModuleName, String attributeName )
        throws SAXException {
        Object obj;
        ServiceSelector selector = null;
        InputModule inputModule = null;
        try {
            selector = (ServiceSelector) this.manager.lookup( InputModule.ROLE + "Selector" );
            inputModule = (InputModule) selector.select( inputModuleName );
            obj = inputModule.getAttribute( attributeName, null, this.objectModel );

        } catch ( ServiceException e ) {
            throw new SAXException( "Could not find an InputModule of the type " + 
                                    inputModuleName , e );
        } catch ( ConfigurationException e ) {
            throw new SAXException( "Could not find an attribute: " + attributeName +
                                    " from the InputModule " + inputModuleName, e );
        } finally {
            if ( inputModule != null ) selector.release( inputModule );
            this.manager.release( selector );
        }

        return obj;
    }

    private void setOutputAttribute( String outputModuleName,
                                     String attributeName, Object value )
        throws SAXException{
        ServiceSelector selector = null;
        OutputModule outputModule = null;
        try {
            selector = (ServiceSelector) this.manager.lookup( OutputModule.ROLE + "Selector" );
            outputModule = (OutputModule) selector.select( outputModuleName );
            outputModule.setAttribute( null, this.objectModel, attributeName, value );
            outputModule.commit( null, this.objectModel );

        } catch ( ServiceException e ) {
            throw new SAXException( "Could not find an OutputModule of the type " + 
                                    outputModuleName , e );
        } finally {
            if ( outputModule != null ) selector.release( outputModule );
            this.manager.release( selector );
        }
    }
}