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#pragma once

#if THRUST_DEVICE_COMPILER == THRUST_DEVICE_COMPILER_HIP
#include <thrust/system/hip/config.h>

#include <thrust/detail/minmax.h>
#include <thrust/distance.h>
#include <thrust/system/hip/detail/execution_policy.h>

THRUST_NAMESPACE_BEGIN
namespace hip_rocprim
{

// XXX forward declare to circumvent circular depedency
template <class Derived, class InputIt, class Predicate>
InputIt THRUST_HIP_FUNCTION
find_if(execution_policy<Derived>& policy,
        InputIt                    first,
        InputIt                    last,
        Predicate                  predicate);

template <class Derived, class InputIt, class Predicate>
InputIt THRUST_HIP_FUNCTION
find_if_not(execution_policy<Derived>& policy,
            InputIt                    first,
            InputIt                    last,
            Predicate                  predicate);

template <class Derived, class InputIt, class T>
InputIt THRUST_HIP_FUNCTION
find(execution_policy<Derived>& policy, InputIt first, InputIt last, T const& value);

}; // namespace hip_rocprim
THRUST_NAMESPACE_END

#include <thrust/iterator/zip_iterator.h>
#include <thrust/system/hip/detail/reduce.h>

THRUST_NAMESPACE_BEGIN
namespace hip_rocprim
{
namespace __find_if
{
    template <typename TupleType>
    struct functor
    {
        TupleType THRUST_HIP_DEVICE_FUNCTION
        operator()(const TupleType& lhs,
                   const TupleType& rhs) const
        {
            // select the smallest index among true results
            if(thrust::get<0>(lhs) && thrust::get<0>(rhs))
            {
                return TupleType(true, (thrust::min)(thrust::get<1>(lhs), thrust::get<1>(rhs)));
            }
            else if(thrust::get<0>(lhs))
            {
                return lhs;
            }
            else
            {
                return rhs;
            }
        }
    };
} // namespace __find_if

template <class Derived, class InputIt, class Size, class Predicate>
InputIt THRUST_HIP_FUNCTION
find_if_n(execution_policy<Derived>& policy,
          InputIt                    first,
          Size                       num_items,
          Predicate                  predicate)
{
    typedef typename thrust::tuple<bool, Size> result_type;

    // empty sequence
    if(num_items == 0)
        return first;

    // this implementation breaks up the sequence into separate intervals
    // in an attempt to early-out as soon as a value is found
    //
    // XXX compose find_if from a look-back prefix scan algorithm
    //     and abort kernel when the first element is found

    // TODO incorporate sizeof(InputType) into interval_threshold and round to multiple of 32
    const Size interval_threshold = 1 << 20;
    const Size interval_size      = (thrust::min)(interval_threshold, num_items);

    // force transform_iterator output to bool
    typedef transform_input_iterator_t<bool, InputIt, Predicate>   XfrmIterator;
    typedef thrust::tuple<XfrmIterator, counting_iterator_t<Size>> IteratorTuple;
    typedef thrust::zip_iterator<IteratorTuple>                    ZipIterator;

    IteratorTuple iter_tuple
        = thrust::make_tuple(XfrmIterator(first, predicate), counting_iterator_t<Size>(0));

    ZipIterator begin = thrust::make_zip_iterator(iter_tuple);
    ZipIterator end   = begin + num_items;

    for(ZipIterator interval_begin = begin; interval_begin < end;
        interval_begin += interval_size)
    {
        ZipIterator interval_end = interval_begin + interval_size;
        if(end < interval_end)
        {
            interval_end = end;
        } // end if

        result_type result = reduce(policy,
                                    interval_begin,
                                    interval_end,
                                    result_type(false, interval_end - begin),
                                    __find_if::functor<result_type>());

        // see if we found something
        if(thrust::get<0>(result))
        {
            return first + thrust::get<1>(result);
        }
    }

    hip_rocprim::throw_on_error(
        hip_rocprim::synchronize_optional(policy),
        "find_if_n: failed to synchronize"
    );

    //nothing was found if we reach here...
    return first + num_items;
}

template <class Derived, class InputIt, class Predicate>
InputIt THRUST_HIP_FUNCTION
find_if(execution_policy<Derived>& policy,
        InputIt                    first,
        InputIt                    last,
        Predicate                  predicate)
{
    return hip_rocprim::find_if_n(policy, first, thrust::distance(first, last), predicate);
}

template <class Derived, class InputIt, class Predicate>
InputIt THRUST_HIP_FUNCTION
find_if_not(execution_policy<Derived>& policy,
            InputIt                    first,
            InputIt                    last,
            Predicate                  predicate)
{
    return hip_rocprim::find_if(policy, first, last, thrust::detail::not1(predicate));
}

template <class Derived, class InputIt, class T>
InputIt THRUST_HIP_FUNCTION
find(execution_policy<Derived>& policy,
     InputIt                    first,
     InputIt                    last,
     T const&                   value)
{
    using thrust::placeholders::_1;
    return hip_rocprim::find_if(policy,
                                first,
                                last,
                                 _1 == value);
}

} // namespace hip_rocprim
THRUST_NAMESPACE_END
#endif
