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/*******************************************************************************
 * Copyright (c) 2004, 2007 Actuate Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *  Actuate Corporation  - initial API and implementation
 *******************************************************************************/
package org.eclipse.birt.data.engine.olap.cursor;

/**
 * This class is to position along the edge cursor.
 */
class EdgeTraverse
{
	int currentPosition, curPosOnMap;
	private EdgeDimensionRelation relationMap;
	private int edgeStart, edgeEnd, traverseLength;

	EdgeTraverse( EdgeDimensionRelation relationMap )
	{
		this.currentPosition = -1;
		this.relationMap = relationMap;
		this.edgeStart = 0;
		this.edgeEnd = relationMap.traverseLength - 1;
		this.traverseLength = this.relationMap.traverseLength;
	}
	
	EdgeTraverse( EdgeDimensionRelation relationMap, int edgeStart, int edgeEnd )
	{
		this( relationMap );
		this.edgeStart = edgeStart;
		this.edgeEnd = edgeEnd;
		this.traverseLength = edgeEnd - edgeStart + 1;
	}

	/**
	 * Move the cursor to the end of the edge, just after the last row.
	 */
	void afterLast( )
	{
		this.curPosOnMap = edgeEnd + 1;
		this.currentPosition = this.traverseLength;
	}
	
	/**
	 * Move the cursor before the first row of the edge.
	 */
	void beforeFirst( )
	{
		this.curPosOnMap = edgeStart - 1;
		this.currentPosition = - 1;
	}
	
	/**
	 * Move the cursor to the first row of the edge.
	 * @return
	 */
	boolean first( )
	{
		if ( this.traverseLength > 0 )
		{
			this.currentPosition = 0;
			this.curPosOnMap = edgeStart;
			return true;
		}
		else
		{
			return false;
		}
	}
	
	/**
	 * get the current position of edge cursor.
	 * @return
	 */
	int getEdgePostion( )
	{
		return this.currentPosition;	
	}
	
	/**
	 * indicate whether the cursor move after the last row.
	 * @return
	 */
	boolean isAfterLast( )
	{
		return this.currentPosition >= this.traverseLength;
	}
	
	/**
	 * indicate whether the cursor move before the first row
	 * @return
	 */
	boolean isBeforeFirst( )
	{
		return this.currentPosition < 0;
	}
	
	/**
	 * indicate whether the cursor move to the first row
	 * @return
	 */
	boolean isFirst( )
	{
		return this.currentPosition == 0;
	}
	
	/**
	 * indicate whether the cursor move to the last row
	 * @return
	 */
	boolean isLast( )
	{
		return this.currentPosition == this.traverseLength - 1;	
	}
	
	/**
	 * move the cursor to the last row.
	 * @return
	 */
	boolean last( )
	{
		if ( this.relationMap.traverseLength > 0 )
		{
			this.currentPosition = this.traverseLength - 1;
			this.curPosOnMap = this.edgeEnd - 1;
			return true;
		}
		else
		{
			return false;
		}
	}
	
	/**
	 * move the cursor to the next row.
	 * @return
	 */
	boolean next( )
	{
		this.currentPosition++;
		this.curPosOnMap++;
		if ( currentPosition < this.traverseLength )
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	
	/**
	 * move the cursor to the previous row.
	 * @return
	 */
	boolean previous( )
	{
		this.currentPosition--;
		this.curPosOnMap--;
		if ( currentPosition >= 0 )
		{
			return true;
		}
		else
		{
			currentPosition = -1;
			return false;
		}
	}
	
	/**
	 * move the cursor to the relative offset.
	 * @param arg0
	 * @return
	 */
	boolean relative( int arg0 )
	{
		if ( arg0 == 0 )
			return true;
		int position = this.currentPosition + arg0;
		if ( position >= this.relationMap.traverseLength )
		{
			return false;
		}
		else if ( position < 0 )
		{
			this.currentPosition = -1;
			this.curPosOnMap = edgeStart - 1;
			return false;
		}
		else
		{
			this.curPosOnMap = this.curPosOnMap + arg0;
			this.currentPosition = position;
			return true;
		}
	}
}