/**
 * 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.pdfbox.jbig2.image;

import java.awt.image.WritableRaster;

import org.apache.pdfbox.jbig2.Bitmap;

final class BitmapScanline extends Scanline
{

    private Bitmap bitmap;
    private WritableRaster raster;

    private int[] lineBuffer;

    public BitmapScanline(final Bitmap src, final WritableRaster dst, final int width)
    {
        super(width);
        this.bitmap = src;
        this.raster = dst;
        lineBuffer = new int[length];
    }

    @Override
    protected void clear()
    {
        lineBuffer = new int[length];
    }

    @Override
    protected void fetch(int x, final int y)
    {
        lineBuffer = new int[length]; // really required?
        int srcByteIdx = bitmap.getByteIndex(x, y);
        while (x < length)
        {
            final byte srcByte = (byte) ~bitmap.getByte(srcByteIdx++);
            final int bits = bitmap.getWidth() - x > 8 ? 8 : bitmap.getWidth() - x;
            for (int bitPosition = bits - 1; bitPosition >= 0; bitPosition--, x++)
            {
                if (((srcByte >> bitPosition) & 0x1) != 0)
                    lineBuffer[x] = 255;
            }
        }
    }

    @Override
    protected void filter(final int[] preShift, final int[] postShift, final Weighttab[] tabs,
            final Scanline dst)
    {
        final BitmapScanline dstBitmapScanline = (BitmapScanline) dst;
        final int dstLength = dst.length;

        // start sum at 1 << shift - 1 for rounding
        final int start = 1 << postShift[0] - 1;
        final int srcBuffer[] = lineBuffer;
        final int dstBuffer[] = dstBitmapScanline.lineBuffer;

        // the next two blocks are duplicated except for the missing shift operation if preShift == 0.
        final int preShift0 = preShift[0];
        final int postShift0 = postShift[0];
        if (preShift0 != 0)
        {
            for (int dstIndex = 0, tab = 0; tab < dstLength; tab++)
            {
                final Weighttab weightTab = tabs[tab];
                final int weights = weightTab.weights.length;

                int sum = start;
                for (int weightIndex = 0, srcIndex = weightTab.i0; weightIndex < weights
                        && srcIndex < srcBuffer.length; weightIndex++)
                {
                    sum += weightTab.weights[weightIndex] * (srcBuffer[srcIndex++] >> preShift0);
                }

                final int t = sum >> postShift0;
                dstBuffer[dstIndex++] = t < 0 ? 0 : t > 255 ? 255 : t;
            }
        }
        else
        {
            for (int dstIndex = 0, tab = 0; tab < dstLength; tab++)
            {
                final Weighttab weightTab = tabs[tab];
                final int weights = weightTab.weights.length;

                int sum = start;
                for (int weightIndex = 0, srcIndex = weightTab.i0; weightIndex < weights
                        && srcIndex < srcBuffer.length; weightIndex++)
                {
                    sum += weightTab.weights[weightIndex] * srcBuffer[srcIndex++];
                }

                dstBuffer[dstIndex++] = sum >> postShift0;
            }
        }
    }

    @Override
    protected void accumulate(final int weight, final Scanline dst)
    {
        final BitmapScanline dstBitmapScanline = (BitmapScanline) dst;

        final int srcBuffer[] = lineBuffer;
        final int dstBuffer[] = dstBitmapScanline.lineBuffer;

        for (int b = 0; b < dstBuffer.length; b++)
            dstBuffer[b] += weight * srcBuffer[b];
    }

    @Override
    protected void shift(final int[] shift)
    {
        final int shift0 = shift[0];
        final int half = 1 << shift0 - 1;

        final int srcBuffer[] = lineBuffer;

        for (int b = 0; b < srcBuffer.length; b++)
        {
            final int pixel = srcBuffer[b] + half >> shift0;
            srcBuffer[b] = pixel < 0 ? 0 : pixel > 255 ? 255 : pixel;
        }
    }

    @Override
    protected void store(final int x, final int y)
    {
        raster.setSamples(x, y, length, 1, 0, lineBuffer);
    }

}