/*-- $Id$ -- 

 ============================================================================
                   The Apache Software License, Version 1.1
 ============================================================================
 
    Copyright (C) 1999 The Apache Software Foundation. All rights reserved.
 
 Redistribution and use in source and binary forms, with or without modifica-
 tion, are permitted provided that the following conditions are met:
 
 1. Redistributions of  source code must  retain the above copyright  notice,
    this list of conditions and the following disclaimer.
 
 2. Redistributions in binary form must reproduce the above copyright notice,
    this list of conditions and the following disclaimer in the documentation
    and/or other materials provided with the distribution.
 
 3. The end-user documentation included with the redistribution, if any, must
    include  the following  acknowledgment:  "This product includes  software
    developed  by the  Apache Software Foundation  (http://www.apache.org/)."
    Alternately, this  acknowledgment may  appear in the software itself,  if
    and wherever such third-party acknowledgments normally appear.
 
 4. The names "FOP" and  "Apache Software Foundation"  must not be used to
    endorse  or promote  products derived  from this  software without  prior
    written permission. For written permission, please contact
    apache@apache.org.
 
 5. Products  derived from this software may not  be called "Apache", nor may
    "Apache" appear  in their name,  without prior written permission  of the
    Apache Software Foundation.
 
 THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 FITNESS  FOR A PARTICULAR  PURPOSE ARE  DISCLAIMED.  IN NO  EVENT SHALL  THE
 APACHE SOFTWARE  FOUNDATION  OR ITS CONTRIBUTORS  BE LIABLE FOR  ANY DIRECT,
 INDIRECT, INCIDENTAL, SPECIAL,  EXEMPLARY, OR CONSEQUENTIAL  DAMAGES (INCLU-
 DING, BUT NOT LIMITED TO, PROCUREMENT  OF SUBSTITUTE GOODS OR SERVICES; LOSS
 OF USE, DATA, OR  PROFITS; OR BUSINESS  INTERRUPTION)  HOWEVER CAUSED AND ON
 ANY  THEORY OF LIABILITY,  WHETHER  IN CONTRACT,  STRICT LIABILITY,  OR TORT
 (INCLUDING  NEGLIGENCE OR  OTHERWISE) ARISING IN  ANY WAY OUT OF THE  USE OF
 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 This software  consists of voluntary contributions made  by many individuals
 on  behalf of the Apache Software  Foundation and was  originally created by
 James Tauber <jtauber@jtauber.com>. For more  information on the Apache 
 Software Foundation, please see <http://www.apache.org/>.
 
 */

package org.apache.fop.fo.flow;

// FOP
import org.apache.fop.fo.*;
import org.apache.fop.fo.properties.*;
import org.apache.fop.fo.pagination.*;
import org.apache.fop.layout.Area;
import org.apache.fop.layout.BodyAreaContainer;
import org.apache.fop.apps.FOPException;
import org.apache.fop.messaging.MessageHandler;

// Java
import java.util.Hashtable;
import java.util.Enumeration;
import java.util.Vector;

public class Flow extends FObj {
	
    public static class Maker extends FObj.Maker {
	public FObj make(FObj parent, PropertyList propertyList)
	    throws FOPException {
	    return new Flow(parent, propertyList);
	}
    }

    public static FObj.Maker maker() {
	return new Flow.Maker();
    }

    /** PageSequence container */
    private PageSequence pageSequence;

    /**  Area in which we lay out our kids */
    private Area area; 

    /**  Vector to store snapshot */
    private Vector markerSnapshot; 

    /** flow-name attribute */
    private String _flowName;
    
    private Status _status = new Status(Status.AREA_FULL_NONE);
    

    protected Flow(FObj parent, PropertyList propertyList)
	throws FOPException {
	super(parent, propertyList);
	this.name =  getElementName();

	if (parent.getName().equals("fo:page-sequence")) {
	    this.pageSequence = (PageSequence) parent;
	} else {
	    throw new FOPException("flow must be child of "
				   + "page-sequence, not "
				   + parent.getName());
	} 
	setFlowName(getProperty("flow-name").getString());

	// according to communication from Paul Grosso (XSL-List,
	// 001228, Number 406), confusion in spec section 6.4.5 about
	// multiplicity of fo:flow in XSL 1.0 is cleared up - one (1)
	// fo:flow per fo:page-sequence only.
	if (!pageSequence.isFlowSet())
		pageSequence.addFlow(this);
	else
		throw new FOPException("Only a single fo:flow permitted"
		+ " per fo:page-sequence");
    }

    protected void setFlowName(String name)
	throws FOPException
    {
	if (name == null || name.equals("")) {
	    MessageHandler.errorln("WARNING: A 'flow-name' is required for "+getElementName()+". This constraint will be enforced in future versions of FOP");
	    _flowName = "xsl-region-body";
 	}
	else {
	    _flowName = name;
	}
	
    }
    
    public String getFlowName() 
    {
	return _flowName;
    }
    
    public Status layout(Area area) throws FOPException {
	return layout(area, null);
	
    }
    
    public Status layout(Area area, Region region) throws FOPException {
		if (this.marker == START) {
			this.marker = 0;
		}
	
		// flow is *always* laid out into a BodyAreaContainer
		BodyAreaContainer bac = (BodyAreaContainer)area;
		
		boolean prevChildMustKeepWithNext = false;
	
		int numChildren = this.children.size();
		for (int i = this.marker; i < numChildren; i++) {
			FObj fo = (FObj) children.elementAt(i);
			
			if (bac.isBalancingRequired(fo))
			{
				// reset the the just-done span area in preparation
				// for a backtrack for balancing
				bac.resetSpanArea();
				
				this.rollback(markerSnapshot);
				// one less because of the "continue"
				i = this.marker - 1;
				continue;
			}
			// current column area
			Area currentArea = bac.getNextArea(fo);
			// temporary hack for IDReferences
			currentArea.setIDReferences(bac.getIDReferences());
			if (bac.isNewSpanArea())
			{
				this.marker = i;
				markerSnapshot = this.getMarkerSnapshot(new Vector());
			}
			
			_status = fo.layout(currentArea);
			if (_status.isIncomplete()) {
				if ((prevChildMustKeepWithNext) && (_status.laidOutNone())) {
					this.marker = i - 1;
					FObj prevChild = (FObj) children.elementAt(this.marker);
					prevChild.removeAreas();
					prevChild.resetMarker();
					prevChild.removeID(area.getIDReferences());
					_status = new Status(Status.AREA_FULL_SOME);
					return _status;
					// should probably return AREA_FULL_NONE if first
					// or perhaps an entirely new status code
				}
				if (bac.isLastColumn())
					if (_status.getCode() == Status.FORCE_COLUMN_BREAK) {
						this.marker = i;
						_status = new Status(Status.FORCE_PAGE_BREAK);	// same thing
						return _status;
					}
					else {
						this.marker = i;
						return _status;
					}
				else
				{
					// not the last column, but could be page breaks
					if (_status.isPageBreak())
					{
						this.marker = i;
						return _status;
					}
					// I don't much like exposing this. (AHS 001217)
					((org.apache.fop.layout.ColumnArea)currentArea).incrementSpanIndex();
					i--;
				}
			}
			if (_status.getCode() == Status.KEEP_WITH_NEXT) {
				prevChildMustKeepWithNext = true;
			}
			else {
				prevChildMustKeepWithNext = false;
			}
		}
		return _status;
    }

  /**
   * Return the content width of this flow (really of the region
   * in which it is flowing).
   */
  public int getContentWidth() {
    if (area != null)
      return area.getContentWidth(); //getAllocationWidth()??
    else return 0;  // not laid out yet
  }
    
    protected String getElementName() 
    {
	return "fo:flow";
    }
    
    public Status getStatus() 
    {
	return _status;
    }
    

  public boolean generatesReferenceAreas() {
	return true;
  }

}
