/*
 * Data HUb Service (DHuS) - For Space data distribution.
 * Copyright (C) 2013,2014,2015,2016 European Space Agency (ESA)
 * Copyright (C) 2013,2014,2015,2016 GAEL Systems
 * Copyright (C) 2013,2014,2015,2016 Serco Spa
 *
 * This file is part of DHuS software sources.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package fr.gael.drb.cortex.topic.sentinel3.jai.operator;

import org.apache.log4j.Logger;

import fr.gael.drb.DrbNode;
import fr.gael.drb.query.Query;
import fr.gael.drb.value.Float;
import fr.gael.drb.value.Short;
import fr.gael.drb.value.Value;
import fr.gael.drbx.image.DrbCollectionImage;
import fr.gael.drbx.image.DrbImage;

/**
 * Commong class gather the OLCI/SLSTR commons implementations and variables. 
 */
public class Common
{
   private static Logger LOGGER = Logger.getLogger(QuicklookOlciRIF.class);
   public static final int colorRange = 2048 * 3;
   
   /**
    * Extracts per bands, the pixel corrections to be applied. Pixel correction
    * is defined by a scale and an offset to apply as followed:
    * <pre>
    * {@code
    *    pixel = scale*extracted + offset;
    * }
    * </pre>
    * As Drb extracts raw data from netcdf Array. The data corrections are not
    * applied. The following code retrieve pixels informations, letting netcdf
    * library apply all the necessary computations:
    * <pre>
    * {@code
    * NetcdfDataset ds=NetcdfDataset.openDataset("Oa04_radiance.nc");
    * VariableEnhanced data = ds.getVariables("Oa04_radiance");
    * ArrayFloat.D2 dataArray = data.read();
    * }
    * </pre>
    * @param sources the sentinel-3 OLCI datasources.
    * @param band where retrieve the corrections settings(starting from 1).
    * @return the correction data structure.
    * @see PixelCorrection
    */
   public static PixelCorrection extractPixelCorrection (
      DrbCollectionImage sources, int band)
   {
      String name=String.format("Oa%1$02d_radiance", band);
      
      return extractPixelCorrection (sources, name);
   }
   
   public static PixelCorrection extractPixelCorrection (
      DrbCollectionImage sources, String name)
   {
      DrbImage image = sources.getChildren().iterator().next();
      DrbNode node = ((DrbNode)(image.getItemSource()));
      
      return extractPixelCorrection (node, name);
   }
   
   public static PixelCorrection extractPixelCorrection (
      DrbNode product_node, String name)
   {
      String path = "*[name()='" + name  + ".nc']/root/variables/*[name()='" + 
         name + "']/attributes/";
      try
      {
         Query query_pixel_scale  = new Query(path + "scale_factor");
         Query query_pixel_offset = new Query(path + "add_offset");
         Query query_nodata = new Query(path + "_FillValue");
         
         Value vscale = null;
         try
         {
            vscale = query_pixel_scale.evaluate(product_node).getItem(0).
               getValue().convertTo(Value.FLOAT_ID);
         }
         catch (Exception e)
         {
            vscale = new Float(1); 
         }
         Value voffset =null;
         try
         {
            voffset = query_pixel_offset.evaluate(product_node).getItem(0).
               getValue().convertTo(Value.FLOAT_ID);
         }
         catch (Exception e)
         {
            voffset = new Float(0);
         }
         Value vnodata=null; 
         try
         {
            vnodata = query_nodata.evaluate(product_node).getItem(0).
                getValue().convertTo(Value.SHORT_ID);
         }
         catch (Exception e)
         {
            vnodata = new Short(0);
         }
         
         float scale  = ((Float)vscale).floatValue();
         float offset = ((Float)voffset).floatValue();
         short nodata = ((Short)vnodata).shortValue();
      
         return new PixelCorrection(scale, offset, nodata);
      }
      catch (Exception e)
      {
         LOGGER.error("Pixel correction extraction failure.", e);
      }
      return null;
   }
   
   /**
    * Pixel correction contains elements to apply a correction to a pixel.
    */
   public static class PixelCorrection
   {
      public PixelCorrection(float scale, float offset, int nodata)
      {
         this.scale = scale;
         this.offset = offset;
         this.nodata = nodata;
      }
      public float scale;
      public float offset;
      public int nodata;
   }

}