package org.exist.collections.triggers;

import java.io.IOException;
import java.net.URISyntaxException;
import java.util.Date;
import java.util.Map;

import org.exist.collections.Collection;
import org.exist.collections.CollectionConfigurationException;
import org.exist.dom.DocumentImpl;
import org.exist.security.PermissionDeniedException;
import org.exist.storage.DBBroker;
import org.exist.storage.txn.Txn;
import org.exist.util.LockException;
import org.exist.xmldb.XmldbURI;
import org.exist.xquery.XPathException;
import org.exist.xquery.value.DateTimeValue;

/**
 * This collection trigger will save all old versions of documents before
 * they are overwritten or removed. The old versions are kept in the
 * 'history root' which is by default '<code>/db/history</code>', but can be 
 * changed with the parameter '<code>root</code>'.
 * You need to configure this trigger for every collection whose history you
 * want to preserve, by modifying '<code>collection.xconf</code>' such that it
 * resembles this:
 *
 * <pre>
 *   <?xml version='1.0'?>
 *   <collection xmlns='http://exist-db.org/collection-config/1.0'>
 *     <triggers>
 *       <trigger 
 *         event='update'
 *         class='org.exist.collections.triggers.HistoryTrigger'
 *       />
 *       <trigger
 *         event='remove'
 *         class='org.exist.collections.triggers.HistoryTrigger'
 *       />
 *     </triggers>
 *   </collection>
 * </pre>
 *
 * @author Mark Spanbroek
 * @see org.exist.collections.triggers.Trigger
 */
public class HistoryTrigger extends FilteringTrigger implements DocumentTrigger
{

    protected XmldbURI rootPath = XmldbURI.ROOT_COLLECTION_URI.append("history");

    public void configure(DBBroker broker, Collection parent, Map parameters) throws CollectionConfigurationException
    {
        super.configure(broker, parent, parameters);
        
        if(parameters.containsKey("root"))
        {
            try
            {
            	rootPath = XmldbURI.xmldbUriFor(parameters.get("root").toString());
            }
            catch(URISyntaxException e)
            {
            	throw new CollectionConfigurationException(e);
            }
        }
    }
    
    public void prepare(int event, DBBroker broker, Txn transaction, XmldbURI documentName, DocumentImpl doc) throws TriggerException
    {
    	if(doc == null)
    		return;
        
    	// construct the destination path
   	  	XmldbURI path = rootPath.append(doc.getURI());
        
   	  	try
   	  	{
   	  		//construct the destination document name
   	  		String dtValue = new DateTimeValue(new Date(doc.getMetadata().getLastModified())).getStringValue();
   	  		dtValue = dtValue.replaceAll(":", "-"); // multiple ':' are not allowed in URI so use '-'
   	  		dtValue = dtValue.replaceAll("\\.", "-"); // as we are using '-' instead of ':' do the same for '.'
   	  		XmldbURI name = XmldbURI.create(dtValue);
        
   	  		// create the destination document
        
   	  		//TODO : how is the transaction handled ? It holds the locks ! 
   	  		Collection destination = broker.getOrCreateCollection(transaction, path);
   	  		broker.saveCollection(transaction, destination);
   	  		broker.copyResource(transaction, doc, destination, name);
   	  	}
   	  	catch(XPathException xpe)
   	  	{
   	  		throw new TriggerException(xpe);
   	  	}
   	  	catch(IOException exception)
   	  	{
   	  		throw new TriggerException(exception);
   	  	}
   	  	catch(PermissionDeniedException exception)
   	  	{
   	  		throw new TriggerException(exception);
   	  	}
   	  	catch(LockException exception)
   	  	{
   	  		throw new TriggerException(exception);
   	  	}
    }
    
    public void finish(int event, DBBroker broker, Txn transaction, XmldbURI documentPath, DocumentImpl document)
    {
    }
}