
package jp.riken.brain.ni.samuraigraph.base;

import java.util.ArrayList;
import java.util.List;

/**
 * A class to keep the property histories and to control undo/redo operation.
 *
 */
public class SGUndoManager
{

	// an undoable object
	private SGIUndoable mUndoable = null;
	
	// a list of the memento of mUndoable
	private List mMementoList = new ArrayList();

	// the location in the memento series of mUndoable
	private int mMementoCounter = 0;

	// A list of changed objects list, which contains mUndoable
	// and its undoable child objects if they exist.
	private List mChangedObjectListList = new ArrayList();

	// the location in the series of changed objects lists
	private int mChangedObjectListCounter = 0;


	/**
	 * Create this object with an undoable object.
	 * @param obj - an undoable object
	 */
	public SGUndoManager( SGIUndoable obj )
	{
		super();
		this.mUndoable = obj;
	}


	/**
	 * Initialize the history of the undoable object.
	 */
	public boolean initPropertiesHistory()
	{
		return this.addMemento( this.mUndoable.getMemento() );
	}


	/**
	 * Go backward the memento list and set the memento to the undoable object.
	 */
	public boolean setMementoBackward()
	{
		this.mMementoCounter--;
		return this.setCurrentMemento();
	}


	/**
	 * Go forward the memento list and set the memento to the undoable object.
	 */
	public boolean setMementoForward()
	{
		this.mMementoCounter++;
		return this.setCurrentMemento();
	}


	// Set the memento to the undoable object with the current counter values.
	private boolean setCurrentMemento()
	{
		SGProperties p
			= (SGProperties)this.mMementoList.get( this.mMementoCounter );
		return this.mUndoable.setMemento(p);
	}


	/**
	 * Undo the operation.
	 */
	public boolean undo()
	{
		if( this.isUndoable() == false )
		{
			return false;
		}

		ArrayList objList = (ArrayList)this.mChangedObjectListList.get(
			this.mChangedObjectListCounter - 1 );

		for( int ii=0; ii<objList.size(); ii++ )
		{
			SGIUndoable obj = (SGIUndoable)objList.get(ii);
			boolean flag;
			if( obj.equals( this.mUndoable ) )
			{
				flag = this.mUndoable.setMementoBackward();
			}
			else
			{
				flag = obj.undo();
			}
		
			if( !flag )
			{
				throw new Error("undo erorr:"+obj);
			}
		}

		// decrement the counter
		this.mChangedObjectListCounter--;

		return true;
	}



	/**
	 * Redo the operation.
	 */
	public boolean redo()
	{
		if( this.isRedoable() == false )
		{
			return false;
		}

		ArrayList objList = (ArrayList)this.mChangedObjectListList.get(
			this.mChangedObjectListCounter );
		for( int ii=0; ii<objList.size(); ii++ )
		{
			SGIUndoable obj = (SGIUndoable)objList.get(ii);
			boolean flag;
			if( obj.equals( this.mUndoable ) )
			{
				flag = this.mUndoable.setMementoForward();
			}
			else
			{
				flag = obj.redo();
			}

			if( !flag )
			{
				throw new Error("redo erorr:"+obj);
			}
		}

		// increment the counter
		this.mChangedObjectListCounter++;

		return true;
	}



	/**
	 * Update the list of changed objects lists.
	 */
	private boolean updateObjectHistory( final SGIUndoable obj )
	{
		ArrayList objList = new ArrayList();
		objList.add(obj);
		return this.updateObjectHistory(objList);
	}



	/**
	 * Update the list of changed objects lists.
	 */
	private boolean updateObjectHistory( final List objList )
	{
		List hList = this.mChangedObjectListList;
		hList = hList.subList( 0, this.mChangedObjectListCounter );
		hList.add( new ArrayList(objList) );
		this.mChangedObjectListList = hList;
		this.mChangedObjectListCounter++;
		return true;
	}



	/**
	 * Update the histories of the undoable object.
	 * @return
	 */
	public boolean updateHistory()
	{
		if( this.mUndoable.isChanged() )
		{
			// update the memento list of mUndoable
			if( this.updateMementoList() == false )
			{
				return false;
			}

			// clear the changed flag
			this.mUndoable.setChanged( false );

			// add to the changed objects list
			if( this.updateObjectHistory( this.mUndoable ) == false )
			{
				return false;
			}
		}

		return true;
	}



	/**
	 * Update the histories of the undoable object together with given undoable objects.
	 * @param objList - a list of undoable objects
	 * @return
	 */
	public boolean updateHistory( final List objList )
	{
		ArrayList changedObjList = new ArrayList();
		if( this.mUndoable.isChanged() )
		{
			// update the memento list of mUndoable
			if( this.updateMementoList() == false )
			{
				return false;
			}

			// clear the changed flag
			this.mUndoable.setChanged(false);

			// add to the changed objects list
			changedObjList.add( this.mUndoable );
		}

		for( int ii=0; ii<objList.size(); ii++ )
		{
			SGIUndoable obj = (SGIUndoable)objList.get(ii);
			if( obj.isChanged() )
			{
				if( obj.updateHistory() == false )
				{
					return false;
				}
				changedObjList.add(obj);
			}
		}

		if( changedObjList.size()!=0 )
		{
			if( this.updateObjectHistory( changedObjList ) == false )
			{
				return false;
			}
		}

		return true;
	}


	// Update the memento list.
	private boolean updateMementoList()
	{
		this.mMementoCounter++;
		SGProperties p = this.mUndoable.getMemento();
		if( p==null )
		{
			return false;
		}
		return this.addMemento(p);
	}


	// Add a property object to the memento list.
	private boolean addMemento( final SGProperties p )
	{
		List hList = this.mMementoList;
		hList = hList.subList( 0, this.mMementoCounter );
		hList.add(p);
		this.mMementoList = hList;
		return true;
	}


	/**
	 * Return whether this object can undo.
	 * @return
	 */
	public boolean isUndoable()
	{
		return (this.mChangedObjectListCounter!=0);
	}


	/**
	 * Return whether this object can redo.
	 * @return
	 */
	public boolean isRedoable()
	{
		return ( this.mChangedObjectListCounter!=this.mChangedObjectListList.size() );
	}


	/**
	 * Returns the undoable object.
	 * @return - an undoable object
	 */
	public SGIUndoable getUndoable()
	{
		return this.mUndoable;
	}


	public void dump()
	{
		System.out.println("<<" + this.mUndoable + ">>");
		System.out.println( this.mChangedObjectListList );
		System.out.println( this.mChangedObjectListCounter );
		System.out.println( this.mMementoList );
		System.out.println( this.mMementoCounter );
		System.out.println();

//		System.out.println(
//			this.mMementoCounter+"  "
//			+this.mUndoableObjectsListCounter+"  "
//			+this.mMementoList.size()+"  "
//			+this.mUndoableObjectListList.size());
	}

}

