/* Copyright (C) 2001, 2008 United States Government as represented by
   the Administrator of the National Aeronautics and Space Administration.
   All Rights Reserved.
 */

package gov.nasa.worldwind.formats.tiff;

import java.io.IOException;
import java.util.Locale;
import javax.imageio.ImageReader;
import javax.imageio.spi.ImageReaderSpi;
import javax.imageio.stream.ImageInputStream;

/**
 * GeotiffImageReaderSpi is a singleton class. Multiply registering it should be harmless.
 * @author brownrigg
 * @version $Id$
 */
public class GeotiffImageReaderSpi extends ImageReaderSpi {

    public static GeotiffImageReaderSpi inst() { 
        if (theInstance == null) 
            theInstance = new GeotiffImageReaderSpi();
        return theInstance;
    }
    
    private  GeotiffImageReaderSpi() {
        super(vendorName, version, names, suffixes, mimeTypes, 
                readerClassname, STANDARD_INPUT_TYPE,
                null, false, null, null, null, null,
                false, null, null, null, null);
    }
    
    @Override
    public boolean canDecodeInput(Object source) throws IOException {
        if (source == null || !(source instanceof ImageInputStream)) 
            return false;
        
        ImageInputStream inp = (ImageInputStream) source;
        byte[] ifh = new byte[8];  // Tiff image-file header
        try {
            inp.mark();
            inp.readFully(ifh);
            inp.reset();
        } catch(IOException ex)  {
            return false;
        }
        
        return (ifh[0] == 0x4D && ifh[1] == 0x4D && ifh[2] == 0x00 && ifh[3] == 0x2A) ||  // big-endian
               (ifh[0] == 0x49 && ifh[1] == 0x49 && ifh[2] == 0x2A && ifh[3] == 0x00);    // little-endian
    }

    @Override
    public ImageReader createReaderInstance(Object extension) throws IOException {
        return new GeotiffImageReader(this);
    }

    @Override
    public String getDescription(Locale locale) {
        return "NASA WorldWind simplified Geotiff Image Reader";
    }

    private static GeotiffImageReaderSpi theInstance = null;
    
    private static final String vendorName = "NASA WorldWind";
    private static final String version = "1.0";
    private static final String[] names = {"tiff", "GTiff", "geotiff"};
    private static final String[] suffixes = {"tif", "tiff", "gtif"};
    private static final String[] mimeTypes = {"image/geotiff"};
    private static final String readerClassname = "gov.nasa.worldwind.servers.wms.utilities.TiffImageReader";
}