/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 * 
 *    (C) 2004-2008, Open Source Geospatial Foundation (OSGeo)
 *
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Lesser General Public
 *    License as published by the Free Software Foundation;
 *    version 2.1 of the License.
 *
 *    This library is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *    Lesser General Public License for more details.
 */
package org.geotools.geometry.jts;


// JTS dependencies
import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.CoordinateSequence;
import com.vividsolutions.jts.geom.CoordinateSequenceFactory;
import com.vividsolutions.jts.geom.DefaultCoordinateSequenceFactory;
import org.opengis.geometry.MismatchedDimensionException;

// OpenGIS dependencies
import org.opengis.referencing.operation.MathTransform;
import org.opengis.referencing.operation.TransformException;


/**
 * A default implementation of {@linkplain CoordinateSequenceTransformer coordinate sequence
 * transformer}. This transformer applies the coordinate transformations immediately (which
 * means that caller are immediately notified if a transformation fails).
 * <p>
 * This transformer support {@linkplain MathTransform math transform} with up to 3 source
 * or target dimensions. This transformer is not thread-safe.
 *
 * @since 2.1
 *
 * @source $URL$
 * @version $Id$
 * @author Andrea Aime
 * @author Martin Desruisseaux
 */
public class DefaultCoordinateSequenceTransformer implements CoordinateSequenceTransformer {
    /**
     * A buffer for coordinate transformations. We choose a length which is divisible by
     * both 2 and 3, since JTS coordinates may be up to three-dimensional. If the number
     * of coordinates point to transform is greater than the buffer capacity, then the
     * buffer will be flushed to the destination array before to continue. We avoid to
     * create a buffer as large than the number of point to transforms, because it would
     * consume a large amount of memory for big geometries.
     */
    private final transient double[] buffer = new double[96];

    /**
     * The coordinate sequence factory to use.
     */
    private final CoordinateSequenceFactory csFactory;

    /**
     * Constructs a default coordinate sequence transformer.
     */
    public DefaultCoordinateSequenceTransformer() {
        csFactory = DefaultCoordinateSequenceFactory.instance();
    }
    
    public DefaultCoordinateSequenceTransformer(CoordinateSequenceFactory csFactory) {
        this.csFactory = csFactory;
    }

    /**
     * {@inheritDoc}
     */
    public CoordinateSequence transform(final CoordinateSequence sequence,
        final MathTransform transform) throws TransformException {
        final int sourceDim = transform.getSourceDimensions();
        final int targetDim = transform.getTargetDimensions();
        final int size = sequence.size();
        final Coordinate[] tcs = new Coordinate[size];
        final int bufferCapacity = buffer.length / Math.max(sourceDim, targetDim);
        int remainingBeforeFlush = Math.min(bufferCapacity, size);
        int ib = 0; // Index in the buffer array.
        int it = 0; // Index in the target sequence.
        
        // create a target CS so that the dimensions not contemplated in the source CS  
        // are copied over (think Z or M with a 2d CRS)
        int targetCSDim = targetDim + (sequence.getDimension() - sourceDim);
		CoordinateSequence result =  csFactory.create(sequence.size(), targetCSDim);

        for (int i = 0; i < size; i++) {
            switch (sourceDim) {
            default:
                throw new MismatchedDimensionException();

            case 3:
                buffer[ib + 2] = sequence.getOrdinate(i, 2); // Fall through

            case 2:
                buffer[ib + 1] = sequence.getY(i); // Fall through

            case 1:
                buffer[ib] = sequence.getX(i); // Fall through

            case 0:
                break;
            }

            ib += sourceDim;

            if (--remainingBeforeFlush == 0) {
                /*
                 * The buffer is full, or we just copied the last coordinates.
                 * Transform the coordinates and flush to the destination array.
                 */
                assert (ib % sourceDim) == 0;

                final int n = ib / sourceDim;
                transform.transform(buffer, 0, buffer, 0, n);
                ib = 0;

                for (int j = 0; j < n; j++) {
                    final Coordinate t;
                    
                    // copy the transformed portion
                    int oi = 0;
                    for (; oi < targetDim; oi++) {
                        result.setOrdinate(it, oi, buffer[ib++]);   
                    }
                    // copy over the non transformed portion
                    for (; oi < targetCSDim; oi++) {
                        result.setOrdinate(it, oi, sequence.getOrdinate(it, oi + (targetDim - sourceDim)));   
                    }
                    // force to NaN eventual extra ordinates the sequence has (some are fixed size, wont'
                    // care about us trying to tell them a size). This works around a bug in the default
                    // JTS coordinate sequence implementation
                    for (; oi < result.getDimension(); oi++) {
                        result.setOrdinate(it, oi, Double.NaN);   
                    }
                    it++;
                }
                assert ib == (n * targetDim);
                ib = 0;
                remainingBeforeFlush = Math.min(bufferCapacity, size - (i + 1));
            }
        }
        assert it == tcs.length : tcs.length - it;

        return result;
    }
}