/*
    * 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.commons.imaging.formats.bmp;
  
  import java.awt.image.BufferedImage;
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  
  import org.apache.commons.imaging.common.BinaryOutputStream;
  import org.apache.commons.imaging.palette.SimplePalette;
  
  final class BmpWriterPalette implements BmpWriter {
  
      private final SimplePalette palette;
      private final int bitsPerSample;
  
      BmpWriterPalette(final SimplePalette palette) {
          this.palette = palette;
  
          if (palette.length() <= 2) {
              bitsPerSample = 1;
          } else if (palette.length() <= 16) {
              bitsPerSample = 4;
          } else {
              bitsPerSample = 8;
          }
      }
  
      @Override
      public int getBitsPerPixel() {
          return bitsPerSample;
      }
  
      @Override
      public byte[] getImageData(final BufferedImage src) {
          final int width = src.getWidth();
          final int height = src.getHeight();
  
          final ByteArrayOutputStream baos = new ByteArrayOutputStream();
  
          int bitCache = 0;
          int bitsInCache = 0;
  
          int byteCount = 0;
          for (int y = height - 1; y >= 0; y--) {
              for (int x = 0; x < width; x++) {
                  final int argb = src.getRGB(x, y);
                  final int rgb = 0xffffff & argb;
  
                  final int index = palette.getPaletteIndex(rgb);
  
                  if (bitsPerSample == 8) {
                      baos.write(0xff & index);
                      byteCount++;
                  } else {
                      // 4 or 1
                      bitCache = bitCache << bitsPerSample | index;
                      bitsInCache += bitsPerSample;
                      if (bitsInCache >= 8) {
                          baos.write(0xff & bitCache);
                          byteCount++;
                          bitCache = 0;
                          bitsInCache = 0;
                      }
                  }
              }
  
              if (bitsInCache > 0) {
                  bitCache = bitCache << 8 - bitsInCache;
  
                  baos.write(0xff & bitCache);
                  byteCount++;
                  bitCache = 0;
                  bitsInCache = 0;
              }
  
              while (byteCount % 4 != 0) {
                  baos.write(0);
                  byteCount++;
              }
          }
  
          return baos.toByteArray();
      }
  
     @Override
     public int getPaletteSize() {
         return palette.length();
     }
 
     @Override
     public void writePalette(final BinaryOutputStream bos) throws IOException {
         for (int i = 0; i < palette.length(); i++) {
             final int rgb = palette.getEntry(i);
 
             final int red = 0xff & rgb >> 16;
             final int green = 0xff & rgb >> 8;
             final int blue = 0xff & rgb >> 0;
 
             bos.write(blue);
             bos.write(green);
             bos.write(red);
             bos.write(0);
         }
     }
 }