/*
 * 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 org.apache.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()
    {
        super();
    }

    /**
     * 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.
     */
    @Override
    void read(TrueTypeFont ttf, TTFDataStream data) throws IOException
    {
        HorizontalHeaderTable hHeader = ttf.getHorizontalHeader();
        if (hHeader == null)
        {
            throw new IOException("Could not get hmtx table");
        }
        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;
        }

        int numberNonHorizontal = numGlyphs - numHMetrics;

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

        // make sure that table is never null and correct size, even with bad fonts that have no
        // "leftSideBearing" table although they should
        nonHorizontalLeftSideBearing = new short[numberNonHorizontal];

        if (bytesRead < getLength())
        {
            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
     * 
     * @return the advance width of the given GID
     */
    public int getAdvanceWidth(int gid)
    {
        if (advanceWidth.length == 0)
        {
            return 250;
        }
        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];
        }
    }
    
    /**
     * Returns the left side bearing for the given GID.
     *
     * @param gid GID
     * 
     * @return the left side bearing of the given GID
     */
    public int getLeftSideBearing(int gid)
    {
        if (leftSideBearing.length == 0)
        {
            return 0;
        }
        if (gid < numHMetrics)
        {
            return leftSideBearing[gid];
        }
        else
        {
            return nonHorizontalLeftSideBearing[gid - numHMetrics];
        }
   }
}
