#include "filter.h"
 
using namespace std;

template <class S>
void Filter<S>::predict()
{
  for (int i=0; i<cur.size(); ++i)
  {
    // Pick a random number then find it's nearest match(>=) in the cdf
    // TODO check that this works with the cdf
    double choice = (rand()/RAND_MAX )*cdf[cdf.size()-1];
    int low, middle, high;

    low = 0;
    high = cdf.size();

    while (high>(low+1)) {
      middle = (high+low)/2;
      if (choice > cdf[middle])
        low = middle;
      else high = middle;
    }
    
    //FIXME model magic should happen here
    next[i] = cur[low];
  }
}


template <class S>
void Filter<S>::makeCdf()
{
  for (int i=0; i<weight.size(); ++i)
  {
    //FIXME more model specifics
    /*
     * use observations to determine the weight
     */
    weight[i] = 1.0;
    cdf[i] = ( i==0 ? 0 : cdf[i-1] ) + weight[i];
  }
}

template <class S>
void Filter<S>::updateSamples()
{
  observe();
  /*
   * pick some of the old samples and map them to new samples
   * using a model
   * picking is weighted
   */
  predict();
  
  makeCdf();
}