/*
  Copyright 2022 Equinor ASA.

  This file is part of the Open Porous Media project (OPM).

  OPM is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  OPM is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with OPM.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <opm/simulators/flow/ExtraConvergenceOutputThread.hpp>

#include <opm/simulators/flow/ConvergenceOutputConfiguration.hpp>

#include <opm/simulators/timestepping/ConvergenceReport.hpp>

#include <algorithm>
#include <array>
#include <cassert>
#include <condition_variable>
#include <cstddef>
#include <filesystem>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iterator>
#include <limits>
#include <mutex>
#include <numeric>
#include <optional>
#include <ostream>
#include <sstream>
#include <stdexcept>
#include <string>
#include <string_view>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <utility>
#include <vector>

namespace {

    auto fixedHeaders() noexcept
    {
        using namespace std::literals::string_literals;

        return std::array {
            "ReportStep"s,
            "TimeStep"s,
            "Time"s,
            "Iteration"s,
            "CnvPvFracConv"s,
            "CnvPvFracRelax"s,
            "CnvPvFracUnconv"s,
            "CnvCellCntConv"s,
            "CnvCellCntRelax"s,
            "CnvCellCntUnconv"s,
        };
    }

    template <typename HeaderSequence>
    auto maxHeaderSize(const HeaderSequence& headers)
    {
        using sz_t = std::remove_cv_t<std::remove_reference_t<
            decltype(std::declval<HeaderSequence>().front().size())>>;

        if (headers.empty()) {
            return sz_t{0};
        }

        return std::accumulate(headers.begin(), headers.end(), sz_t{1},
                               [](const auto m, const auto& header)
                               {
                                   return std::max(m, header.size() + 1);
                               });
    }

    std::string
    formatMetricColumn(const Opm::ConvergenceOutputThread::ComponentToPhaseName& getPhaseName,
                       const Opm::ConvergenceReport::ReservoirConvergenceMetric& metric)
    {
        std::ostringstream os;
        os << to_string(metric.type()) << '_' << getPhaseName(metric.phase());

        return os.str();
    }

    std::string::size_type
    maxColHeaderSize(const std::string::size_type                                           minColSize,
                     const Opm::ConvergenceOutputThread::ComponentToPhaseName&              getPhaseName,
                     const std::vector<Opm::ConvergenceReport::ReservoirConvergenceMetric>& cols)
    {
        return std::accumulate(cols.begin(), cols.end(), minColSize,
            [&getPhaseName](const std::string::size_type                              maxChar,
                            const Opm::ConvergenceReport::ReservoirConvergenceMetric& metric)
        {
            return std::max(maxChar, formatMetricColumn(getPhaseName, metric).size() + 1);
        });
    }

    std::pair<std::string::size_type, std::string::size_type>
    writeConvergenceHeader(std::ostream&                                             os,
                           const Opm::ConvergenceOutputThread::ComponentToPhaseName& getPhaseName,
                           const Opm::ConvergenceReportQueue::OutputRequest&         firstRequest)
    {
        const auto initial_headers = fixedHeaders();
        const auto minColSize = maxHeaderSize(initial_headers);

        {
            auto leadingSpace = false;

            for (const auto& columnHeader : initial_headers) {
                if (leadingSpace) { os << ' '; }
                os << std::right << std::setw(minColSize) << columnHeader;
                leadingSpace = true;
            }
        }

        const auto& metrics    = firstRequest.reports.front().reservoirConvergence();
        const auto  headerSize = maxColHeaderSize(minColSize, getPhaseName, metrics);

        for (const auto& metric : metrics) {
            os << std::right << std::setw(headerSize)
               << formatMetricColumn(getPhaseName, metric);
        }

        // Note: Newline character intentionally placed in separate output
        // request to not influence right-justification of column header.
        os << std::right << std::setw(headerSize) << "WellStatus" << '\n';

        return { minColSize, headerSize };
    }

    void writeTimeColumns(std::ostream&                                           os,
                          const Opm::ConvergenceOutputThread::ConvertToTimeUnits& convertTime,
                          const std::string::size_type                            firstColSize,
                          const int                                               iter,
                          const Opm::ConvergenceReport&                           report,
                          const Opm::ConvergenceReportQueue::OutputRequest&       request)
    {
        os << std::setw(firstColSize)          << request.reportStep  << ' '
           << std::setw(firstColSize)          << request.currentStep << ' '
           << std::setprecision(4)             << std::setw(firstColSize)
           << convertTime(report.reportTime()) << ' '
           << std::setw(firstColSize)          << iter;
    }

    void writeCnvPvSplit(std::ostream&                        os,
                         const std::vector<double>::size_type expectedNumValues,
                         const std::string::size_type         firstColSize,
                         const Opm::ConvergenceReport&        report)
    {
        const auto& [splitPv, cellCnt] = report.cnvPvSplit();

        if (splitPv.size() == expectedNumValues) {
            for (const auto& pv : splitPv) {
                os << ' ' << std::setprecision(4) << std::setw(firstColSize)
                   << pv / report.eligiblePoreVolume();
            }
        }
        else {
            constexpr auto val = std::numeric_limits<double>::has_quiet_NaN
                ? std::numeric_limits<double>::quiet_NaN()
                : -1.0;

            for (auto i = 0*expectedNumValues; i < expectedNumValues; ++i) {
                os << ' ' << std::setprecision(4) << std::setw(firstColSize) << val;
            }
        }

        if (cellCnt.size() == expectedNumValues) {
            for (const auto& cnt : cellCnt) {
                os << ' ' << std::setw(firstColSize) << cnt;
            }
        }
        else {
            for (auto i = 0*expectedNumValues; i < expectedNumValues; ++i) {
                os << ' ' << std::setw(firstColSize) << -1;
            }
        }
    }

    void writeReservoirConvergence(std::ostream&                 os,
                                   const std::string::size_type  colSize,
                                   const Opm::ConvergenceReport& report)
    {
        for (const auto& metric : report.reservoirConvergence()) {
            os << std::setprecision(4) << std::setw(colSize) << metric.value();
        }
    }

    void writeWellConvergence(std::ostream&                 os,
                              const std::string::size_type  colSize,
                              const Opm::ConvergenceReport& report)
    {
        os << std::right << std::setw(colSize)
           << (report.wellFailed() ? "FAIL" : "CONV");

        if (report.wellFailed()) {
            for (const auto& wf : report.wellFailures()) {
                os << ' ' << to_string(wf);
            }
        }
    }

    void writeConvergenceRequest(std::ostream&                                           os,
                                 const Opm::ConvergenceOutputThread::ConvertToTimeUnits& convertTime,
                                 const std::string::size_type                            firstColSize,
                                 const std::string::size_type                            colSize,
                                 const Opm::ConvergenceReportQueue::OutputRequest&       request)
    {
        os.setf(std::ios_base::scientific);

        const auto expectNumCnvSplit = std::vector<double>::size_type{3};

        auto iter = 0;
        for (const auto& report : request.reports) {
            writeTimeColumns(os, convertTime, firstColSize, iter, report, request);

            writeCnvPvSplit(os, expectNumCnvSplit, firstColSize, report);

            writeReservoirConvergence(os, colSize, report);
            writeWellConvergence(os, colSize, report);

            os << '\n';

            ++iter;
        }
    }
} // Anonymous namespace

// ---------------------------------------------------------------------------

class Opm::ConvergenceOutputThread::Impl
{
public:
    explicit Impl(std::string_view               outputDir,
                  std::string_view               baseName,
                  ComponentToPhaseName           getPhaseName,
                  ConvertToTimeUnits             convertTime,
                  ConvergenceOutputConfiguration config,
                  ConvergenceReportQueue&        queue);

    ConvergenceReportQueue& queue()
    {
        return this->queue_;
    }

    void write(const std::vector<ConvergenceReportQueue::OutputRequest>& requests);
    bool finalRequestWritten() const
    {
        return this->finalRequestWritten_;
    }

private:
    std::reference_wrapper<ConvergenceReportQueue> queue_;
    ComponentToPhaseName getPhaseName_{};
    ConvertToTimeUnits convertTime_{};
    std::optional<std::ofstream> infoIter_{};
    std::string::size_type firstColSize_{0};
    std::string::size_type colSize_{0};
    bool haveOutputIterHeader_{false};
    bool finalRequestWritten_{false};

    void writeIterInfo(const std::vector<ConvergenceReportQueue::OutputRequest>& requests);
};

Opm::ConvergenceOutputThread::Impl::Impl(std::string_view               outputDir,
                                         std::string_view               baseName,
                                         ComponentToPhaseName           getPhaseName,
                                         ConvertToTimeUnits             convertTime,
                                         ConvergenceOutputConfiguration config,
                                         ConvergenceReportQueue&        queue)
    : queue_        { std::ref(queue) }
    , getPhaseName_ { std::move(getPhaseName) }
    , convertTime_  { std::move(convertTime) }
{
    if (config.want(ConvergenceOutputConfiguration::Option::Iterations)) {
        this->infoIter_.emplace
            (std::filesystem::path { outputDir } /
             std::filesystem::path { baseName }.concat(".INFOITER"));
    }
}

void
Opm::ConvergenceOutputThread::Impl::
write(const std::vector<ConvergenceReportQueue::OutputRequest>& requests)
{
    assert (! requests.empty() &&
            "Internal logic error in forming convergence output request");

    this->writeIterInfo(requests);
}

void
Opm::ConvergenceOutputThread::Impl::
writeIterInfo(const std::vector<ConvergenceReportQueue::OutputRequest>& requests)
{
    if (! this->infoIter_.has_value()) {
        return;
    }

    if (! this->haveOutputIterHeader_) {
        std::tie(this->firstColSize_, this->colSize_) =
            writeConvergenceHeader(this->infoIter_.value(),
                                   this->getPhaseName_,
                                   requests.front());
        this->haveOutputIterHeader_ = true;
    }

    for (const auto& request : requests) {
        writeConvergenceRequest(this->infoIter_.value(),
                                this->convertTime_,
                                this->firstColSize_,
                                this->colSize_,
                                request);

        if (request.reports.empty()) {
            this->finalRequestWritten_ = true;
            break;
        }
    }

    this->infoIter_.value().flush();
}

// ===========================================================================
// Public Interface Below Separator
// ===========================================================================

void Opm::ConvergenceReportQueue::enqueue(std::vector<OutputRequest>&& requests)
{
    // Signal output thread if we're going from "no work" to "some work".
    // We don't need to signal if we're going from "some work" to "more
    // work".
    auto must_notify = false;

    {
        std::lock_guard<std::mutex> guard{ this->mtx_ };
        must_notify = this->requests_.empty();
        this->requests_.insert(this->requests_.end(),
                               std::make_move_iterator(requests.begin()),
                               std::make_move_iterator(requests.end()));
    }

    if (must_notify) {
        this->cv_.notify_one();
    }
}

void Opm::ConvergenceReportQueue::signalLastOutputRequest()
{
    // Empty request signals end of production.
    this->enqueue(std::vector<OutputRequest>(1));
}

// ---------------------------------------------------------------------------

Opm::ConvergenceOutputThread::
ConvergenceOutputThread(std::string_view               outputDir,
                        std::string_view               baseName,
                        ComponentToPhaseName           getPhaseName,
                        ConvertToTimeUnits             convertTime,
                        ConvergenceOutputConfiguration config,
                        ConvergenceReportQueue&        queue)
    : pImpl_ { std::make_unique<Impl>(outputDir,
                                      baseName,
                                      getPhaseName,
                                      convertTime,
                                      config,
                                      queue) }
{}

Opm::ConvergenceOutputThread::~ConvergenceOutputThread() = default;

Opm::ConvergenceOutputThread::ConvergenceOutputThread(ConvergenceOutputThread&& src)
    : pImpl_ { std::move(src.pImpl_) }
{}

void
Opm::ConvergenceOutputThread::
writeSynchronous(std::vector<ConvergenceReportQueue::OutputRequest>&& requests)
{
    this->pImpl_->write(requests);
}

void Opm::ConvergenceOutputThread::writeASynchronous()
{
    // This is the main function of the convergence output thread.  It runs
    // for the duration of the process, although mostly in an idle/waiting
    // state.  Implementation from Microsoft's "GoingNative" show, episode
    // 53, on threading and parallelism in the STL.

    auto& queue = this->pImpl_->queue();

    // Note: Loop terminates only when final request written.
    for (auto localReq = std::vector<ConvergenceReportQueue::OutputRequest>{} ; ; localReq.clear()) {
        std::unique_lock<std::mutex> lock { queue.mtx_ };
        queue.cv_.wait(lock, [&queue]() { return !queue.requests_.empty(); });

        // Capture all pending output requests, relinquish lock and write
        // file output outside of the critical section.
        queue.requests_.swap(localReq);

        lock.unlock();

        this->pImpl_->write(localReq);

        if (this->pImpl_->finalRequestWritten()) {
            // No more output coming.  Shut down thread.
            return;
        }
    }
}