/*
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * The Original Code is the Kowari Metadata Store.
 *
 * The Initial Developer of the Original Code is Plugged In Software Pty
 * Ltd (http://www.pisoftware.com, mailto:info@pisoftware.com). Portions
 * created by Plugged In Software Pty Ltd are Copyright (C) 2001,2002
 * Plugged In Software Pty Ltd. All Rights Reserved.
 *
 * Contributor(s): N/A.
 *
 * [NOTE: The text of this Exhibit A may differ slightly from the text
 * of the notices in the Source Code files of the Original Code. You
 * should use the text of this Exhibit A rather than the text found in the
 * Original Code Source Code for Your Modifications.]
 *
 */

package org.mulgara.resolver;

// Java 2 standard packages
import java.io.InputStream;
import java.net.URI;

import javax.activation.MimeType;

import org.apache.log4j.Logger;
import org.mulgara.content.Content;
import org.mulgara.content.ContentHandler;
import org.mulgara.content.ContentHandlerException;
import org.mulgara.content.ContentHandlerManager;
import org.mulgara.query.QueryException;
import org.mulgara.query.rdf.URIReferenceImpl;
import org.mulgara.resolver.spi.DatabaseMetadata;
import org.mulgara.resolver.spi.Resolver;
import org.mulgara.resolver.spi.Statements;
import org.mulgara.resolver.spi.SystemResolver;

/**
 * An {@link Operation} that implements the
 * {@link org.mulgara.server.Session#setModel(URI, URI)} and
 * {@link org.mulgara.server.Session#setModel(InputStream, URI, URI, MimeType)} methods.
 *
 * @created 2004-11-04
 *
 * @author <a href="http://staff.pisoftware.com/raboczi">Simon Raboczi</a>
 *
 * @version $Revision: 1.10 $
 *
 * @modified $Date: 2005/05/02 20:07:56 $ by $Author: raboczi $
 *
 * @maintenanceAuthor $Author: raboczi $
 *
 * @copyright ©2004 <a href="http://www.tucanatech.com/">Tucana
 *   Technology, Inc</a>
 *
 * @licence <a href="{@docRoot}/../../LICENCE">Mozilla Public License v1.1</a>
 */
class SetGraphOperation implements Operation {

  /** Logger. */
  private static final Logger logger = Logger.getLogger(SetGraphOperation.class.getName());

  private final URI         sourceUri;
  private final URI         destinationUri;
  private final InputStream inputStream;
  private final MimeType    contentType;

  private final ContentHandlerManager contentHandlers;

  /**
   * Number of statements loaded, or -1 if the {@link #execute} method hasn't yet been
   * invoked.
   */
  private long statementCount = -1;

  //
  // Constructor
  //

  /**
   * @param sourceUri The URI of the new content, which might double as its location.
   * @param destinationUri The URI of the graph being set.
   * @param inputStream The content to load, or <tt>null</tt> to de-reference the source URI.
   * @param contentType The content type, or <tt>null</tt> if unknown.
   * @param contentHandlers The content handler manager to find the correct parser.
   */
  SetGraphOperation(URI         sourceUri,
                    URI         destinationUri,
                    InputStream inputStream,
                    MimeType    contentType,
                    ContentHandlerManager contentHandlers)
  {
    this.sourceUri      = sourceUri;
    this.destinationUri     = destinationUri;
    this.inputStream      = inputStream;
    this.contentType      = contentType;
    this.contentHandlers  = contentHandlers;
  }

  //
  // Methods implementing Operation
  //

  public void execute(OperationContext       operationContext,
                      SystemResolver         systemResolver,
                      DatabaseMetadata       metadata) throws Exception
  {
    // A prior call to execute will have set statementCount >= 0.
    if (statementCount != -1) {
      throw new IllegalStateException("SetGraphOperation already executed.  Cannot reexecute.");
    }

    Content content;
    // create a StreamContent if an inputStream has been supplied
    if (inputStream != null) {
      if (logger.isDebugEnabled()) {
        logger.debug("Detected inputstream associated with " + sourceUri );
      }
      content = new StreamContent(inputStream, sourceUri, contentType);
    } else {
      try {
        content = ContentFactory.getContent(sourceUri);
      } catch (ContentHandlerException ec) {
        throw new QueryException("Failed to find Content for uri", ec);
      }
    }
    
    long destinationModel = systemResolver.localize(new URIReferenceImpl(destinationUri));

    // update the destination to the canonical form
    destinationModel = operationContext.getCanonicalModel(destinationModel);

    // Obtain a resolver for the destination model type
    Resolver destinationResolver = operationContext.obtainResolver(
      operationContext.findModelResolverFactory(destinationModel));
    assert destinationResolver != null;

    ContentHandler contentHandler = contentHandlers.getContentHandler(content);

    Statements statements = contentHandler.parse(content,
        new PersistentResolverSession(systemResolver));

    if (logger.isDebugEnabled()) {
      logger.debug("Modifying " + destinationUri + " using " + destinationResolver);
    }

    destinationResolver.modifyModel(destinationModel, statements, true);
    if (logger.isDebugEnabled()) {
      logger.debug("Modified " + destinationUri);
    }

    statementCount = statements.getRowCount();
  }

  /**
   * @return <code>true</code>
   */
  public boolean isWriteOperation() {
    return true;
  }


  //
  // Operation result accessor
  //

  /**
   * @return the number of statements loaded
   * @throws IllegalStateException  if {@link #execute} hasn't yet been called
   */
  long getStatementCount()
  {
    if (statementCount == -1) {
      throw new IllegalStateException("Statement count not available before execution.");
    }

    return statementCount;
  }

}