/*-- $Id$
 * Copyright (C) 2001 The Apache Software Foundation. All rights reserved.
 * For details on use and redistribution please refer to the
 * LICENSE file included with these sources.
 */

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()) {
	    if (this.name.equals("fo:flow")) {
		throw new FOPException("Only a single fo:flow permitted"
				       + " per fo:page-sequence");
	    }
	    else {
		throw new FOPException(this.name+" not allowed after fo:flow");
	    }
	}
	pageSequence.addFlow(this);
    }

    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;
		Vector pageMarker = this.getMarkerSnapshot(new Vector());

		int numChildren = this.children.size();
		if (numChildren == 0)
		{
			throw new FOPException("fo:flow must contain block-level children");
		}
		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.isPageBreak() || i == numChildren - 1) && bac.needsFootnoteAdjusting()) {
		        bac.adjustFootnoteArea();
		        this.rollback(pageMarker);
		        i = this.marker - 1;
		        Area mainReferenceArea = bac.getMainReferenceArea();
		        // remove areas
		        continue;
		    }*/
			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;
  }

}