/******************************************************************************
 * ips4o/sequential.hpp
 *
 * In-place Parallel Super Scalar Samplesort (IPS⁴o)
 *
 ******************************************************************************
 * BSD 2-Clause License
 *
 * Copyright © 2017, Michael Axtmann <michael.axtmann@kit.edu>
 * Copyright © 2017, Daniel Ferizovic <daniel.ferizovic@student.kit.edu>
 * Copyright © 2017, Sascha Witt <sascha.witt@kit.edu>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *****************************************************************************/

#pragma once

#include <utility>

#include "ips4o_fwd.hpp"
#include "base_case.hpp"
#include "memory.hpp"
#include "partitioning.hpp"

namespace ips4o {
namespace detail {

/**
 * Recursive entry point for sequential algorithm.
 */
template <class Cfg>
void Sorter<Cfg>::sequential(const iterator begin, const iterator end) {
    // Check for base case
    const auto n = end - begin;
    if (n <= 2 * Cfg::kBaseCaseSize) {
        detail::baseCaseSort(begin, end, local_.classifier.getComparator());
        return;
    }
    diff_t bucket_start[Cfg::kMaxBuckets + 1];

    // Do the partitioning
    const auto res = partition<false>(begin, end, bucket_start, nullptr, 0, 1);
    const int num_buckets = std::get<0>(res);
    const bool equal_buckets = std::get<1>(res);

    // Final base case is executed in cleanup step, so we're done here
    if (n <= Cfg::kSingleLevelThreshold) {
        return;
    }

    // Recurse
    for (int i = 0; i < num_buckets; i += 1 + equal_buckets) {
        const auto start = bucket_start[i];
        const auto stop = bucket_start[i + 1];
        if (stop - start > 2 * Cfg::kBaseCaseSize)
            sequential(begin + start, begin + stop);
    }
    if (equal_buckets) {
        const auto start = bucket_start[num_buckets - 1];
        const auto stop = bucket_start[num_buckets];
        if (stop - start > 2 * Cfg::kBaseCaseSize)
            sequential(begin + start, begin + stop);
    }
}

}  // namespace detail

/**
 * Reusable sequential sorter.
 */
template <class Cfg>
class SequentialSorter {
    using Sorter = detail::Sorter<Cfg>;
    using iterator = typename Cfg::iterator;

 public:
    explicit SequentialSorter(typename Cfg::less comp)
            : buffer_storage_(1)
            , local_ptr_(Cfg::kDataAlignment, std::move(comp), buffer_storage_.get()) {}

    explicit SequentialSorter(typename Cfg::less comp, char* buffer_storage)
            : local_ptr_(Cfg::kDataAlignment, std::move(comp), buffer_storage) {}

    void operator()(iterator begin, iterator end) {
        Sorter(local_ptr_.get()).sequential(std::move(begin), std::move(end));
    }

 private:
    typename Sorter::BufferStorage buffer_storage_;
    detail::AlignedPtr<typename Sorter::LocalData> local_ptr_;
};

}  // namespace ips4o
