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/*
 * $Id$ $Revision$ $Date$
 * 
 * ==============================================================================
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package wicket.extensions.markup.html.tree.table;

import java.io.Serializable;

import wicket.util.lang.EnumeratedType;

/**
 * This class represents location of a column in tree table.
 * 
 * First attribute of location is alignment. Alignment specifies,
 * whether the column is located on the left side of the table, on the right
 * side, or in the middle. Columns in the middle of the table take all space
 * between columns on the left and columns on the right.
 * 

 * Next two attributes are size and unit:
 * 

 *  For columns aligned to the left and to the right, the size
 * represents the actual width of the column, according to chosen unit. Possible
 * units for left and right aligned columns are PX, EM
 * and PERCENT. 
 *  For columns in the middle, the only valid unit is PROPORTIONAL.
 * These columns take all available space between columns on the left and
 * columns on the right. How this space is divided between middle columns is
 * determined by the size. In this case the size can be understand as
 * weight. Columns with bigger size take more space than columns with smaller
 * size. For example, if there are three columns and their sizes are 2, 1, 1,
 * the first column thakes 50% of the space and the second two columns take 25%
 * each. 
 * 
 * 
 * @author Matej Knopp
 */
public class ColumnLocation implements Serializable
{
	/**
	 * Alignment of the column.
	 */
	public static final class Alignment extends EnumeratedType
	{
		/** Align left. */
		public static final Alignment LEFT = new Alignment("LEFT");

		/** Align middle. */
		public static final Alignment MIDDLE = new Alignment("MIDDLE");

		/** Align right. */
		public static final Alignment RIGHT = new Alignment("RIGHT");

		private static final long serialVersionUID = 1L;

		/**
		 * Construct.
		 * 
		 * @param name
		 */
		public Alignment(String name)
		{
			super(name);
		}
	}

	/**
	 * Units.
	 */
	public static final class Unit extends EnumeratedType
	{

		/** Size of letter M in the current font. */
		public static Unit EM = new Unit("EM");

		/** Percentage. */
		public static Unit PERCENT = new Unit("PERCENT");

		/** Proportional. */
		public static Unit PROPORTIONAL = new Unit("PROPORTIONAL");

		/** Pixels. */
		public static Unit PX = new Unit("PX");

		private static final long serialVersionUID = 1L;

		/**
		 * Construct.
		 * 
		 * @param name
		 */
		public Unit(String name)
		{
			super(name);
		}
	};

	private static final long serialVersionUID = 1L;;

	private Alignment alignment;
	private int size;
	private Unit unit;

	/**
	 * Constructs the ColumnLocation object.
	 * 
	 * @param alignment
	 *            The column alignment
	 * @param size
	 *            The column size in expressed in the provided unit
	 * @param unit
	 *            The unit that the size argument is expressed in
	 * @throws IllegalArgumentException
	 *             if the unit does not matche the alignment
	 */
	public ColumnLocation(Alignment alignment, int size, Unit unit)
	{
		this.alignment = alignment;
		this.size = size;
		this.unit = unit;

		if (alignment == Alignment.MIDDLE && unit != Unit.PROPORTIONAL)
		{
			throw new IllegalArgumentException(
					"For alignment MIDDLE the specified unit must be PROPORTIONAL.");
		}
		else if (alignment != Alignment.MIDDLE && unit == Unit.PROPORTIONAL)
		{
			throw new IllegalArgumentException(
					"Unit PROPORTIONAL can be specified only for columns with alignment MIDDLE.");
		}
	}

	/**
	 * Returns the allignment of this column.
	 * 
	 * @return The alignment of this column
	 */
	public Alignment getAlignment()
	{
		return alignment;
	}

	/**
	 * Returns the size of this column.
	 * 
	 * @return The size of this column
	 */
	public int getSize()
	{
		return size;
	}

	/**
	 * Returns the unit of a column.
	 * 
	 * @return The unit of this column
	 */
	public Unit getUnit()
	{
		return unit;
	}
}