/*
 *  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.
 */

/*! \file trivial_sequence.h
 *  \brief Container-like class for wrapping sequences.  The wrapped
 *         sequence always has trivial iterators, even when the input
 *         sequence does not.
 */

#pragma once

#include <thrust/detail/config.h>

#include <thrust/detail/execution_policy.h>
#include <thrust/detail/temporary_array.h>
#include <thrust/detail/type_traits.h>
#include <thrust/iterator/iterator_traits.h>
#include <thrust/sequence_access.h>
#include <thrust/type_traits/is_contiguous_iterator.h>

THRUST_NAMESPACE_BEGIN

namespace detail
{

// never instantiated
template <typename Iterator, typename DerivedPolicy, typename is_trivial>
struct _trivial_sequence
{};

// trivial case
template <typename Iterator, typename DerivedPolicy>
struct _trivial_sequence<Iterator, DerivedPolicy, thrust::detail::true_type>
{
  using iterator_type = Iterator;
  Iterator first, last;

  THRUST_HOST_DEVICE _trivial_sequence(thrust::execution_policy<DerivedPolicy>&, Iterator _first, Iterator _last)
      : first(_first)
      , last(_last)
  {}

  THRUST_HOST_DEVICE iterator_type begin()
  {
    return first;
  }

  THRUST_HOST_DEVICE friend iterator_type begin(_trivial_sequence& sequence)
  {
    return sequence.first;
  }

  THRUST_HOST_DEVICE iterator_type end()
  {
    return last;
  }

  THRUST_HOST_DEVICE friend iterator_type end(_trivial_sequence& sequence)
  {
    return sequence.first;
  }
};

// non-trivial case
template <typename Iterator, typename DerivedPolicy>
struct _trivial_sequence<Iterator, DerivedPolicy, thrust::detail::false_type>
{
  using iterator_value = typename thrust::iterator_value<Iterator>::type;
  using iterator_type  = typename thrust::detail::temporary_array<iterator_value, DerivedPolicy>::iterator;

  thrust::detail::temporary_array<iterator_value, DerivedPolicy> buffer;

  THRUST_HOST_DEVICE _trivial_sequence(thrust::execution_policy<DerivedPolicy>& exec, Iterator first, Iterator last)
      : buffer(exec, first, last)
  {}

  THRUST_HOST_DEVICE iterator_type begin()
  {
    return buffer.begin();
  }

  THRUST_HOST_DEVICE friend iterator_type begin(_trivial_sequence& sequence)
  {
    return sequence.begin();
  }

  THRUST_HOST_DEVICE iterator_type end()
  {
    return buffer.end();
  }

  THRUST_HOST_DEVICE friend iterator_type end(_trivial_sequence& sequence)
  {
    return sequence.end();
  }
};

template <typename Iterator, typename DerivedPolicy>
struct trivial_sequence
    : detail::_trivial_sequence<Iterator, DerivedPolicy, typename thrust::is_contiguous_iterator<Iterator>::type>
{
  using super_t = _trivial_sequence<Iterator, DerivedPolicy, typename thrust::is_contiguous_iterator<Iterator>::type>;

  THRUST_HOST_DEVICE trivial_sequence(thrust::execution_policy<DerivedPolicy>& exec, Iterator first, Iterator last)
      : super_t(exec, first, last)
  {}
};

} // end namespace detail

THRUST_NAMESPACE_END
