/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 com.tom_roush.fontbox.ttf;

import java.io.IOException;

/**
 * A table in a true type font.
 * 
 * @author Ben Litchfield
 */
public class HorizontalMetricsTable extends TTFTable
{
	/**
	 * A tag that identifies this table type.
	 */
	public static final String TAG = "hmtx";

	private int[] advanceWidth;
	private short[] leftSideBearing;
	private short[] nonHorizontalLeftSideBearing;
	private int numHMetrics;

    HorizontalMetricsTable(TrueTypeFont font)
    {
        super(font);
    }

	/**
	 * This will read the required data from the stream.
	 * 
	 * @param ttf The font that is being read.
	 * @param data The stream to read the data from.
	 * @throws IOException If there is an error reading the data.
	 */
	public void read(TrueTypeFont ttf, TTFDataStream data) throws IOException
	{
		HorizontalHeaderTable hHeader = ttf.getHorizontalHeader();
		numHMetrics = hHeader.getNumberOfHMetrics();
		int numGlyphs = ttf.getNumberOfGlyphs();

		int bytesRead = 0;
		advanceWidth = new int[ numHMetrics ];
		leftSideBearing = new short[ numHMetrics ];
		for( int i=0; i<numHMetrics; i++ )
		{
			advanceWidth[i] = data.readUnsignedShort();
			leftSideBearing[i] = data.readSignedShort();
			bytesRead += 4;
		}

		if (bytesRead < getLength())
		{
			int numberNonHorizontal = numGlyphs - numHMetrics;

			// handle bad fonts with too many hmetrics
			if (numberNonHorizontal < 0)
			{
				numberNonHorizontal = numGlyphs;
			}

			nonHorizontalLeftSideBearing = new short[ numberNonHorizontal ];
			for( int i=0; i<numberNonHorizontal; i++ )
			{
				if (bytesRead < getLength())
				{
					nonHorizontalLeftSideBearing[i] = data.readSignedShort();
					bytesRead += 2;
				}
			}
		}

		initialized = true;
	}

	/**
	 * Returns the advance width for the given GID.
	 *
	 * @param gid GID
	 */
	public int getAdvanceWidth(int gid)
	{
		if (gid < numHMetrics)
		{
			return advanceWidth[gid];
		}
		else
		{
			// monospaced fonts may not have a width for every glyph
			// the last one is for subsequent glyphs
			return advanceWidth[advanceWidth.length -1];
		}
	}
}