/// \file
// Range v3 library
//
//  Copyright Eric Niebler 2014-present
//
//  Use, modification and distribution is subject to the
//  Boost Software License, Version 1.0. (See accompanying
//  file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt)
//
// Project home: https://github.com/ericniebler/range-v3
//
//===----------------------------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef RANGES_V3_ALGORITHM_SEARCH_HPP
#define RANGES_V3_ALGORITHM_SEARCH_HPP

#include <meta/meta.hpp>
#include <range/v3/range_fwd.hpp>
#include <range/v3/range/traits.hpp>
#include <range/v3/range/access.hpp>
#include <range/v3/range/concepts.hpp>
#include <range/v3/range/primitives.hpp>
#include <range/v3/functional/comparisons.hpp>
#include <range/v3/functional/identity.hpp>
#include <range/v3/functional/invoke.hpp>
#include <range/v3/iterator/operations.hpp>
#include <range/v3/iterator/concepts.hpp>
#include <range/v3/iterator/traits.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/view/subrange.hpp>

namespace ranges
{
    /// \addtogroup group-algorithms
    /// @{
    struct search_fn
    {
    private:
        template<typename I1, typename S1, typename D1, typename I2, typename S2, typename D2,
            typename C, typename P1, typename P2>
        static subrange<I1> sized_impl(I1 const begin1_, S1 end1, D1 const d1_,
            I2 begin2, S2 end2, D2 d2, C &pred, P1 &proj1, P2 &proj2)
        {
            D1 d1 = d1_;
            auto begin1 = uncounted(begin1_);
            while(true)
            {
                // Find begin element in sequence 1 that matches *begin2, with a mininum of loop checks
                while(true)
                {
                    if(d1 < d2)  // return the end if we've run out of room
                    {
                        auto e = ranges::next(
                            recounted(begin1_, std::move(begin1), d1_ - d1),
                            std::move(end1));
                        return {e, e};
                    }
                    if(invoke(pred, invoke(proj1, *begin1), invoke(proj2, *begin2)))
                        break;
                    ++begin1;
                    --d1;
                }
                // *begin1 matches *begin2, now match elements after here
                auto m1 = begin1;
                I2 m2 = begin2;
                while(true)
                {
                    if(++m2 == end2)  // If pattern exhausted, begin1 is the answer (works for 1 element pattern)
                    {
                        return {recounted(begin1_, std::move(begin1), d1_ - d1),
                                recounted(begin1_, std::move(++m1), d1_ - d1)};
                    }
                    ++m1;  // No need to check, we know we have room to match successfully
                    if(!invoke(pred, invoke(proj1, *m1), invoke(proj2, *m2)))  // if there is a mismatch, restart with a new begin1
                    {
                        ++begin1;
                        --d1;
                        break;
                    }  // else there is a match, check next elements
                }
            }
        }

        template<typename I1, typename S1, typename I2, typename S2, typename C,
            typename P1, typename P2>
        static subrange<I1> impl(I1 begin1, S1 end1, I2 begin2, S2 end2, C &pred,
            P1 &proj1, P2 &proj2)
        {
            while(true)
            {
                // Find begin element in sequence 1 that matches *begin2, with a mininum of loop checks
                while(true)
                {
                    if(begin1 == end1)  // return end1 if no element matches *begin2
                        return {begin1, begin1};
                    if(invoke(pred, invoke(proj1, *begin1), invoke(proj2, *begin2)))
                        break;
                    ++begin1;
                }
                // *begin1 matches *begin2, now match elements after here
                I1 m1 = begin1;
                I2 m2 = begin2;
                while(true)
                {
                    if(++m2 == end2)  // If pattern exhausted, begin1 is the answer (works for 1 element pattern)
                        return {begin1, ++m1};
                    if(++m1 == end1)  // Otherwise if source exhausted, pattern not found
                        return {m1, m1};
                    if(!invoke(pred, invoke(proj1, *m1), invoke(proj2, *m2)))  // if there is a mismatch, restart with a new begin1
                    {
                        ++begin1;
                        break;
                    }  // else there is a match, check next elements
                }
            }
        }
    public:
        template<typename I1, typename S1, typename I2, typename S2, typename C = equal_to,
            typename P1 = identity, typename P2 = identity>
        auto operator()(I1 begin1, S1 end1, I2 begin2, S2 end2,
                C pred = C{}, P1 proj1 = P1{}, P2 proj2 = P2{}) const ->
            CPP_ret(subrange<I1>)(
                requires ForwardIterator<I1> && Sentinel<S1, I1> &&
                    ForwardIterator<I2> && Sentinel<S2, I2> &&
                    IndirectlyComparable<I1, I2, C, P1, P2>)
        {
            if(begin2 == end2)
                return {begin1, begin1};
            if RANGES_CONSTEXPR_IF (SizedSentinel<S1, I1> && SizedSentinel<S2, I2>)
                return search_fn::sized_impl(std::move(begin1), std::move(end1),
                    distance(begin1, end1), std::move(begin2), std::move(end2),
                    distance(begin2, end2), pred, proj1, proj2);
            else
                return search_fn::impl(std::move(begin1), std::move(end1),
                    std::move(begin2), std::move(end2), pred, proj1, proj2);
        }

        template<typename Rng1, typename Rng2, typename C = equal_to, typename P1 = identity,
            typename P2 = identity>
        auto operator()(Rng1 &&rng1, Rng2 &&rng2, C pred = C{}, P1 proj1 = P1{},
                P2 proj2 = P2{}) const ->
            CPP_ret(safe_subrange_t<Rng1>)(
                requires ForwardRange<Rng1> && ForwardRange<Rng2> &&
                    IndirectlyComparable<iterator_t<Rng1>, iterator_t<Rng2>, C, P1, P2>)
        {
            if(empty(rng2))
                return subrange<iterator_t<Rng1>>{begin(rng1), begin(rng1)};
            if RANGES_CONSTEXPR_IF (SizedRange<Rng1> && SizedRange<Rng2>)
                return search_fn::sized_impl(begin(rng1), end(rng1), distance(rng1),
                    begin(rng2), end(rng2), distance(rng2), pred, proj1, proj2);
            else
                return search_fn::impl(begin(rng1), end(rng1),
                    begin(rng2), end(rng2), pred, proj1, proj2);
        }
    };

    /// \sa `search_fn`
    /// \ingroup group-algorithms
    RANGES_INLINE_VARIABLE(search_fn, search)

    namespace cpp20
    {
        using ranges::search;
    }
    /// @}
} // namespace ranges

#endif // include guard
