/**
 *  \file IMP/algebra/vector_metrics.h   \brief Functions to generate vectors.
 *
 *  Copyright 2007-2013 IMP Inventors. All rights reserved.
 *
 */

#ifndef IMPALGEBRA_VECTOR_METRICS_H
#define IMPALGEBRA_VECTOR_METRICS_H

#include "VectorD.h"
#include "BoundingBoxD.h"
#include <IMP/base/types.h>
#include <IMP/base/Object.h>
#include <iostream>
#include <IMP/base/Pointer.h>
#include <IMP/base/WeakPointer.h>
#include <algorithm>
#include <numeric>

IMPALGEBRA_BEGIN_NAMESPACE

/** The base class for a metric on VectorKDs.
 */
class IMPALGEBRAEXPORT VectorKDMetric: public base::Object {
public:
  VectorKDMetric(std::string name);
  virtual double get_distance(const VectorKD &a,
                              const VectorKD &b) const=0;
  virtual VectorKD get_centroid(const VectorKDs &vs) const=0;
};

IMP_OBJECTS(VectorKDMetric, VectorKDMetrics);

/** The l2 norm on the distance vector.
 */
class IMPALGEBRAEXPORT EuclideanVectorKDMetric: public VectorKDMetric {
public:
  EuclideanVectorKDMetric(std::string name="EuclideanVectorKDMetric%1%");
  double get_distance(const VectorKD &a,
                      const VectorKD &b) const {
    return get_l2_norm(a-b);
  }
  VectorKD get_centroid(const VectorKDs &vs) const {
    IMP_USAGE_CHECK(!vs.empty(), "Needs things to have a centroid");
    VectorKD sum =  std::accumulate(vs.begin(), vs.end(),
                                    get_zero_vector_kd(vs[0].get_dimension()));
    return sum / vs.size();
  }
  IMP_OBJECT_INLINE(EuclideanVectorKDMetric,IMP_UNUSED(out),);
};



/** The l-infinity norm on the difference between the two vectors. And the
    centroid is the center of the bounding box of the vectors.
 */
class IMPALGEBRAEXPORT MaxVectorKDMetric: public VectorKDMetric {
public:
  MaxVectorKDMetric(std::string name="MaxVectorKDMetric%1%");
  double get_distance(const VectorKD &a,
                      const VectorKD &b) const {
    return get_linf_norm(a-b);
  }
  VectorKD get_centroid(const VectorKDs &vs) const {
    IMP_USAGE_CHECK(!vs.empty(), "Needs things to have a centroid");
    BoundingBoxKD bb= std::accumulate(vs.begin(), vs.end(),
                                      BoundingBoxKD(vs[0].get_dimension()));
    return .5*(bb.get_corner(0)+bb.get_corner(1));
  }
  IMP_OBJECT_INLINE(MaxVectorKDMetric,IMP_UNUSED(out),);
};

IMPALGEBRA_END_NAMESPACE

#endif  /* IMPALGEBRA_VECTOR_METRICS_H */