/**
 * Orthanc - A Lightweight, RESTful DICOM Store
 * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
 * Department, University Hospital of Liege, Belgium
 * Copyright (C) 2017-2020 Osimis S.A., Belgium
 *
 * 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/>.
 **/


#include "ViewerPrefetchPolicy.h"

#include "ViewerToolbox.h"
#include "Cache/CacheScheduler.h"

#include <json/value.h>
#include <json/reader.h>



static const Json::Value::ArrayIndex PREFETCH_FORWARD = 10;
static const Json::Value::ArrayIndex PREFETCH_BACKWARD = 3;


namespace OrthancPlugins
{
  void ViewerPrefetchPolicy::ApplySeries(std::list<CacheIndex>& toPrefetch,
                                         CacheScheduler& cache,
                                         const std::string& series,
                                         const std::string& content)
  {
    Json::Value json;
    Json::Reader reader;
    if (!reader.parse(content, json) ||
        !json.isMember("Slices"))
    {
      return;
    }

    const Json::Value& instances = json["Slices"];
    if (instances.type() != Json::arrayValue)
    {
      return;
    }

    for (Json::Value::ArrayIndex i = 0; 
         i < instances.size() && i < PREFETCH_FORWARD; 
         i++)
    {
      std::string item = "jpeg95-" + instances[i].asString();
      toPrefetch.push_back(CacheIndex(CacheBundle_DecodedImage, item));
    }
  }


  void ViewerPrefetchPolicy::ApplyInstance(std::list<CacheIndex>& toPrefetch,
                                           CacheScheduler& cache,
                                           const std::string& path)
  {
    size_t separator = path.find('-');
    if (separator == std::string::npos)
    {
      return;
    }

    std::string compression = path.substr(0, separator + 1);
    std::string instanceAndFrame = path.substr(separator + 1);

    std::string instanceId = instanceAndFrame.substr(0, instanceAndFrame.find('_'));

    Json::Value instance;
    if (!GetJsonFromOrthanc(instance, context_, "/instances/" + instanceId) ||
        !instance.isMember("ParentSeries"))
    {
      return;
    }

    std::string tmp;
    if (!cache.Access(tmp, CacheBundle_SeriesInformation, instance["ParentSeries"].asString()))
    {
      return;
    }
    
    Json::Value series;
    Json::Reader reader;
    if (!reader.parse(tmp, series) ||
        !series.isMember("Slices"))
    {
      return;
    }

    const Json::Value& instances = series["Slices"];

    if (instances.type() != Json::arrayValue)
    {
      return;
    }

    Json::Value::ArrayIndex position = 0;
    while (position < instances.size())
    {
      if (instances[position] == instanceAndFrame)
      {
        break;
      }

      position++;
    }

    if (position == instances.size())
    {
      return;
    }

    for (Json::Value::ArrayIndex i = position;
         i < instances.size() && i < position + PREFETCH_FORWARD; 
         i++)
    {
      std::string item = compression + instances[i].asString();
      toPrefetch.push_back(CacheIndex(CacheBundle_DecodedImage, item));
    }

    for (Json::Value::ArrayIndex i = position;
         i >= 0 && i > position - PREFETCH_BACKWARD; )
    {
      i--;
      std::string item = compression + instances[i].asString();
      toPrefetch.push_back(CacheIndex(CacheBundle_DecodedImage, item));
    }
  }


  void ViewerPrefetchPolicy::Apply(std::list<CacheIndex>& toPrefetch,
                                   CacheScheduler& cache,
                                   const CacheIndex& accessed,
                                   const std::string& content)
  {
    switch (accessed.GetBundle())
    {
      case CacheBundle_SeriesInformation:
        ApplySeries(toPrefetch, cache, accessed.GetItem(), content);
        return;

      case CacheBundle_DecodedImage:
        ApplyInstance(toPrefetch, cache, accessed.GetItem());
        return;

      default:
        return;
    }
  }
}