/*
    * 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.png.chunks;
  
  import java.nio.charset.StandardCharsets;
  
  import org.apache.commons.imaging.ImagingException;
  import org.apache.commons.imaging.common.BinaryFunctions;
  
  public class PngChunkScal extends PngChunk {
  
      private final double unitsPerPixelXAxis;
      private final double unitsPerPixelYAxis;
      private final int unitSpecifier;
  
      public PngChunkScal(final int length, final int chunkType, final int crc, final byte[] bytes) throws ImagingException {
          super(length, chunkType, crc, bytes);
  
          unitSpecifier = bytes[0];
          if (getUnitSpecifier() != 1 && getUnitSpecifier() != 2) {
              throw new ImagingException("PNG sCAL invalid unit specifier: " + getUnitSpecifier());
          }
  
          final int separator = BinaryFunctions.findNull(bytes, "PNG sCAL x and y axis value separator not found.");
          final int xIndex = 1;
          final String xStr = new String(bytes, xIndex, separator - 1, StandardCharsets.ISO_8859_1);
          unitsPerPixelXAxis = toDouble(xStr);
  
          final int yIndex = separator + 1;
          if (yIndex >= length) {
              throw new ImagingException("PNG sCAL chunk missing the y axis value.");
          }
  
          final String yStr = new String(bytes, yIndex, length - yIndex, StandardCharsets.ISO_8859_1);
          unitsPerPixelYAxis = toDouble(yStr);
      }
  
      public int getUnitSpecifier() {
          return unitSpecifier;
      }
  
      public double getUnitsPerPixelXAxis() {
          return unitsPerPixelXAxis;
      }
  
      public double getUnitsPerPixelYAxis() {
          return unitsPerPixelYAxis;
      }
  
      private double toDouble(final String str) throws ImagingException {
          try {
              return Double.parseDouble(str);
          } catch (final NumberFormatException e) {
              throw new ImagingException("PNG sCAL error reading axis value - " + str);
          }
      }
  }