/*
 * Moonlight|3D Copyright (C) 2005 The Moonlight|3D team
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 * 
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 * 
 * Created on Jan 5, 2005
 */
package ml.backend.og;

import java.util.ArrayList;

import ml.core.exceptions.Exception;

/**
 * This class represents a link between an output slot and an input slot of two
 * different operator graph nodes
 * 
 * @author gregor
 */
public class Link {
    ArrayList<Slot> inputs;
    ArrayList<Slot> outputs;
    
    public Link()
    {
        inputs=new ArrayList<Slot>();
        outputs=new ArrayList<Slot>();
    }
    
    /**
     * sets the Slot that is expected to deliver the input
     * for this Link. The Slot has to be an Output Slot of
     * a Node.
     */
    public void setInput(Slot slot) throws ml.core.exceptions.Exception
    {
        if(slot.getType()==Slot.Type.Input) {
            throw new ml.core.exceptions.Exception("unable to assign an input slot to a link input");
        }
          
        slot.setCurrentLink(this);

        if(inputs.size()>0) {
            inputs.remove(inputs.size()-1);
        }
        inputs.add(slot);
    }
    
    /**
     * returns the current Input Slot for this Link.
     */
    public Slot getInput()
    {
        return inputs.get(inputs.size()-1);
    }
    
    /**
     * sets the Slot that is expected to recieve the output
     * of this Link. The Slot has to be an Input Slot of a
     * Node.
     * @throws Exception 
     */
    public void setOutput(Slot slot) throws Exception
    {
        if(slot.getType()==Slot.Type.Output) {
            throw new ml.core.exceptions.Exception("unable to assign an output slot to a link output");
        }
          
        slot.setCurrentLink(this);

        if(outputs.size()>0) {
            outputs.remove(outputs.size()-1);
        }
        outputs.add(slot);
    }
    /**
     * returns the current Output Slot for this link.
     */
    public Slot getOutput()
    {
        return outputs.get(outputs.size()-1);
    }
    
    /**
     * This function passes a recursive update request on to
     * this Link's output slot.
     * @throws Exception 
     */
    public void recursiveUpdate(Manager manager) throws Exception
    {
        getOutput().recursiveUpdate(manager);
    }
    /**
     * Creates a snapshot of the current Input and Output Slots
     * that are assigned to this link in order to allow for an 
     * undo operation lateron.
     */
    public void createUndoSnapshot()
    {
        inputs.add(inputs.get(inputs.size()-1));
        outputs.add(outputs.get(outputs.size()-1));
        
        if(inputs.size()>10) {
            inputs.remove(0);
        }
        if(outputs.size()>10) {
            outputs.remove(0);
        }
    }
     /**
     * Reverts the state of this Link to the latest undo snapshot
     * taken using createUndoSnapshot.
     */
    public void undo()
    {
        inputs.remove(inputs.size()-1);
        outputs.remove(outputs.size()-1);
    }
}