/* -*- mode: c++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

/*

 Copyright (C) 2001, 2002, 2003 Sadruddin Rejeb

 Copyright (C) 2005, 2007 StatPro Italia srl

 This file is part of QuantLib, a free-software/open-source library

 for financial quantitative analysts and developers - http://quantlib.org/

 QuantLib is free software: you can redistribute it and/or modify it

 under the terms of the QuantLib license.  You should have received a

 copy of the license along with this program; if not, please email

 <quantlib-dev@lists.sf.net>. The license is also available online at

 <https://www.quantlib.org/license.shtml>.

 This program 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 license for more details.

*/

#include <ql/pricingengines/swaption/discretizedswaption.hpp>

#include <ql/pricingengines/swaption/treeswaptionengine.hpp>

#include <utility>

namespace QuantLib {

    TreeSwaptionEngine::TreeSwaptionEngine(const ext::shared_ptr<ShortRateModel>& model,

                                           Size timeSteps,

                                           Handle<YieldTermStructure> termStructure)

    : LatticeShortRateModelEngine<Swaption::arguments, Swaption::results>(model, timeSteps),

      termStructure_(std::move(termStructure)) {

        registerWith(termStructure_);

    }

    TreeSwaptionEngine::TreeSwaptionEngine(const ext::shared_ptr<ShortRateModel>& model,

                                           const TimeGrid& timeGrid,

                                           Handle<YieldTermStructure> termStructure)

    : LatticeShortRateModelEngine<Swaption::arguments, Swaption::results>(model, timeGrid),

      termStructure_(std::move(termStructure)) {

        registerWith(termStructure_);

    }

    TreeSwaptionEngine::TreeSwaptionEngine(const Handle<ShortRateModel>& model,

                                           Size timeSteps,

                                           Handle<YieldTermStructure> termStructure)

    : LatticeShortRateModelEngine<Swaption::arguments, Swaption::results>(model, timeSteps),

      termStructure_(std::move(termStructure)) {

        registerWith(termStructure_);

    }

    void TreeSwaptionEngine::calculate() const {

        QL_REQUIRE(arguments_.settlementMethod != Settlement::ParYieldCurve,

                   "cash settled (ParYieldCurve) swaptions not priced with "

                   "TreeSwaptionEngine");

        QL_REQUIRE(!model_.empty(), "no model specified");

        Date referenceDate;

        DayCounter dayCounter;

        ext::shared_ptr<TermStructureConsistentModel> tsmodel =

            ext::dynamic_pointer_cast<TermStructureConsistentModel>(*model_);

        if (tsmodel != nullptr) {

            referenceDate = tsmodel->termStructure()->referenceDate();

            dayCounter = tsmodel->termStructure()->dayCounter();

        } else {

            referenceDate = termStructure_->referenceDate();

            dayCounter = termStructure_->dayCounter();

        }

        DiscretizedSwaption swaption(arguments_, referenceDate, dayCounter);

        ext::shared_ptr<Lattice> lattice;

        if (lattice_ != nullptr) {

            lattice = lattice_;

        } else {

            std::vector<Time> times = swaption.mandatoryTimes();

            TimeGrid timeGrid(times.begin(), times.end(), timeSteps_);

            lattice = model_->tree(timeGrid);

        }

        std::vector<Time> stoppingTimes(arguments_.exercise->dates().size());

        for (Size i=0; i<stoppingTimes.size(); ++i)

            stoppingTimes[i] =

                dayCounter.yearFraction(referenceDate,

                                        arguments_.exercise->date(i));

        swaption.initialize(lattice, stoppingTimes.back());

        Time nextExercise =

            *std::find_if(stoppingTimes.begin(), stoppingTimes.end(),

                          [](Time t){ return t >= 0.0; });

        swaption.rollback(nextExercise);

        results_.value = swaption.presentValue();

    }

}