/*
 *  Copyright 2008-2013 NVIDIA Corporation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#pragma once

#include <thrust/detail/config.h>

#include <thrust/detail/copy.h>
#include <thrust/detail/temporary_array.h>
#include <thrust/iterator/detail/minimum_system.h>
#include <thrust/iterator/iterator_traits.h>
#include <thrust/system/cpp/detail/execution_policy.h>

THRUST_NAMESPACE_BEGIN

namespace detail
{

template <typename InputIterator, typename OutputIterator>
OutputIterator sequential_copy(InputIterator first, InputIterator last, OutputIterator result)
{
  for (; first != last; ++first, ++result)
  {
    *result = *first;
  } // end for

  return result;
} // end sequential_copy()

template <typename BidirectionalIterator1, typename BidirectionalIterator2>
BidirectionalIterator2
sequential_copy_backward(BidirectionalIterator1 first, BidirectionalIterator1 last, BidirectionalIterator2 result)
{
  // yes, we preincrement
  // the ranges are open on the right, i.e. [first, last)
  while (first != last)
  {
    *--result = *--last;
  } // end while

  return result;
} // end sequential_copy_backward()

namespace dispatch
{

template <typename DerivedPolicy, typename RandomAccessIterator1, typename RandomAccessIterator2>
RandomAccessIterator2 overlapped_copy(
  thrust::system::cpp::detail::execution_policy<DerivedPolicy>&,
  RandomAccessIterator1 first,
  RandomAccessIterator1 last,
  RandomAccessIterator2 result)
{
  if (first < last && first <= result && result < last)
  {
    // result lies in [first, last)
    // it's safe to use std::copy_backward here
    thrust::detail::sequential_copy_backward(first, last, result + (last - first));
    result += (last - first);
  } // end if
  else
  {
    // result + (last - first) lies in [first, last)
    // it's safe to use sequential_copy here
    result = thrust::detail::sequential_copy(first, last, result);
  } // end else

  return result;
} // end overlapped_copy()

template <typename DerivedPolicy, typename RandomAccessIterator1, typename RandomAccessIterator2>
RandomAccessIterator2 overlapped_copy(
  thrust::execution_policy<DerivedPolicy>& exec,
  RandomAccessIterator1 first,
  RandomAccessIterator1 last,
  RandomAccessIterator2 result)
{
  using value_type = typename thrust::iterator_value<RandomAccessIterator1>::type;

  // make a temporary copy of [first,last), and copy into it first
  thrust::detail::temporary_array<value_type, DerivedPolicy> temp(exec, first, last);
  return thrust::copy(exec, temp.begin(), temp.end(), result);
} // end overlapped_copy()

} // namespace dispatch

template <typename RandomAccessIterator1, typename RandomAccessIterator2>
RandomAccessIterator2
overlapped_copy(RandomAccessIterator1 first, RandomAccessIterator1 last, RandomAccessIterator2 result)
{
  using System1 = typename thrust::iterator_system<RandomAccessIterator2>::type;
  using System2 = typename thrust::iterator_system<RandomAccessIterator2>::type;

  using System = typename thrust::detail::minimum_system<System1, System2>::type;

  // XXX presumes System is default constructible
  System system;

  return thrust::detail::dispatch::overlapped_copy(system, first, last, result);
} // end overlapped_copy()

} // namespace detail

THRUST_NAMESPACE_END
