#pragma once

#ifndef TCG_ALGORITHM_H
#define TCG_ALGORITHM_H

// tcg includes
#include "traits.h"

// STD includes
#include <functional>

/*!
  \file     algorithm.h

  \brief    This file contains useful algorithms complementary to those
            in the standard \p \<algorithm\> and in \p boost::algorithm.
*/

namespace tcg {

//***************************************************************************
//    Binary find  algorithms
//***************************************************************************

/*!
  \brief    Performs a binary search for the a value in a <I>sorted,
            random access</I> iterators range, and returns its position.

  \return   The \a first range position whose value is \a equivalent to
            the specified one.
*/
template <typename RanIt, typename T>
RanIt binary_find(RanIt begin,     //!< Start of the sorted range.
                  RanIt end,       //!< End of the sorted range.
                  const T &value)  //!< Value to look up.
{
  RanIt it = std::lower_bound(begin, end, value);
  return (it != end && !(value < *it)) ? it : end;
}

//---------------------------------------------------------------------

/*!
  \brief    Performs a binary search for the a value in a <I>sorted,
            random access</I> iterators range, and returns its position.

  \return   The \a first range position whose value is \a equivalent to
            the specified one.
*/
template <typename RanIt, typename T, typename Compare>
RanIt binary_find(RanIt begin,     //!< Start of the sorted range.
                  RanIt end,       //!< End of the sorted range.
                  const T &value,  //!< Value to look up.
                  Compare comp)    //!< Comparator functor sorting the range.
{
  RanIt it = std::lower_bound(begin, end, value, comp);
  return (it != end && !comp(value, *it)) ? it : end;
}

//***************************************************************************
//    Min/Max iterator range  algorithms
//***************************************************************************

/*!
  \brief    Calculates the minimal transformed element from the
            input iterators range.

  \return   The position of the minimal transform.

  \details  This function is similar to std::min_element(), but
            operating a unary transforming function on dereferenced
            objects.

            Furthermore, the minimal transformed value is cached
            during computation.
*/
template <typename ForIt, typename Func, typename Comp>
ForIt min_transform(
    ForIt begin,  //!< Start of the input iterators range.
    ForIt end,    //!< End of the input iterators range.
    Func func,    //!< The transforming function.
    Comp comp)    //!< The comparator object for transformed values.
{
  typedef typename tcg::function_traits<Func>::ret_type ret_type;
  typedef typename tcg::remove_cref<ret_type>::type value_type;

  if (begin == end) return end;

  ForIt minPos       = begin;
  value_type minimum = func(*begin);

  for (; begin != end; ++begin) {
    const value_type &candidate = func(*begin);

    if (comp(candidate, minimum)) minPos = begin, minimum = candidate;
  }

  return minPos;
}

//---------------------------------------------------------------------

/*!
  \brief    Calculates the minimal transformed element from the
            input iterators range.

  \return   The position of the minimal transform.

  \remark   This variation uses \p operator< as comparator for the
            transformed values.
*/
template <typename ForIt, typename Func>
ForIt min_transform(ForIt begin,  //!< Start of the input iterators range.
                    ForIt end,    //!< End of the input iterators range.
                    Func func)    //!< The transforming function.
{
  typedef typename tcg::function_traits<Func>::ret_type ret_type;
  typedef typename tcg::remove_cref<ret_type>::type value_type;

  return min_transform(begin, end, func, std::less<value_type>());
}

//---------------------------------------------------------------------

/*!
  \brief    Calculates the maximal transformed element from the
            input iterators range.

  \return   The position of the maximal transform.

  \sa       See min_transform() for a detailed explanation.
*/
template <typename ForIt, typename Func, typename Comp>
ForIt max_transform(
    ForIt begin,  //!< Start of the input iterators range.
    ForIt end,    //!< End of the input iterators range.
    Func func,    //!< The transforming function.
    Comp comp)    //!< The comparator object for transformed values.
{
  typedef typename tcg::function_traits<Func>::ret_type ret_type;
  typedef typename tcg::remove_cref<ret_type>::type value_type;

  if (begin == end) return end;

  ForIt maxPos       = begin;
  value_type maximum = func(*begin);

  for (; begin != end; ++begin) {
    const value_type &candidate = func(*begin);

    if (comp(maximum, candidate)) maxPos = begin, maximum = candidate;
  }

  return maxPos;
}

//---------------------------------------------------------------------

/*!
  \brief    Calculates the maximal transformed element from the
            input iterators range.

  \return   The position of the maximal transform.

  \sa       See min_transform() for a detailed explanation.
*/
template <typename ForIt, typename Func>
ForIt max_transform(ForIt begin,  //!< Start of the input iterators range.
                    ForIt end,    //!< End of the input iterators range.
                    Func func)    //!< The transforming function.
{
  typedef typename tcg::function_traits<Func>::ret_type ret_type;
  typedef typename tcg::remove_cref<ret_type>::type value_type;

  return max_transform(begin, end, func, std::less<value_type>());
}

}  // namespace tcg

#endif  // TCG_ALGORITHM_H