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

/*
 Copyright (C) 2003 Ferdinando Ametrano
 Copyright (C) 2008 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.
*/

/*! \file quantotermstructure.hpp
    \brief Quanto term structure
*/

#ifndef quantlib_quanto_term_structure_hpp
#define quantlib_quanto_term_structure_hpp

#include <ql/termstructures/volatility/equityfx/blackvoltermstructure.hpp>
#include <ql/termstructures/yield/zeroyieldstructure.hpp>
#include <utility>

namespace QuantLib {

    //! Quanto term structure
    /*! Quanto term structure for modelling quanto effect in
        option pricing.

        \note This term structure will remain linked to the original
              structures, i.e., any changes in the latters will be
              reflected in this structure as well.
    */
    class QuantoTermStructure : public ZeroYieldStructure {
      public:
        QuantoTermStructure(const Handle<YieldTermStructure>& underlyingDividendTS,
                            Handle<YieldTermStructure> riskFreeTS,
                            Handle<YieldTermStructure> foreignRiskFreeTS,
                            Handle<BlackVolTermStructure> underlyingBlackVolTS,
                            Real strike,
                            Handle<BlackVolTermStructure> exchRateBlackVolTS,
                            Real exchRateATMlevel,
                            Real underlyingExchRateCorrelation);
        //! \name YieldTermStructure interface
        //@{
        DayCounter dayCounter() const override;
        Calendar calendar() const override;
        Natural settlementDays() const override;
        const Date& referenceDate() const override;
        Date maxDate() const override;
        //@}
      protected:
        //! returns the zero yield as seen from the evaluation date
        Rate zeroYieldImpl(Time) const override;

      private:
        Handle<YieldTermStructure> underlyingDividendTS_, riskFreeTS_,
                                   foreignRiskFreeTS_;
        Handle<BlackVolTermStructure> underlyingBlackVolTS_,
                                      exchRateBlackVolTS_;
        Real underlyingExchRateCorrelation_, strike_, exchRateATMlevel_;
    };


    // inline definitions

    inline QuantoTermStructure::QuantoTermStructure(
        const Handle<YieldTermStructure>& underlyingDividendTS,
        Handle<YieldTermStructure> riskFreeTS,
        Handle<YieldTermStructure> foreignRiskFreeTS,
        Handle<BlackVolTermStructure> underlyingBlackVolTS,
        Real strike,
        Handle<BlackVolTermStructure> exchRateBlackVolTS,
        Real exchRateATMlevel,
        Real underlyingExchRateCorrelation)
    : ZeroYieldStructure(underlyingDividendTS->dayCounter()),
      underlyingDividendTS_(underlyingDividendTS), riskFreeTS_(std::move(riskFreeTS)),
      foreignRiskFreeTS_(std::move(foreignRiskFreeTS)),
      underlyingBlackVolTS_(std::move(underlyingBlackVolTS)),
      exchRateBlackVolTS_(std::move(exchRateBlackVolTS)),
      underlyingExchRateCorrelation_(underlyingExchRateCorrelation), strike_(strike),
      exchRateATMlevel_(exchRateATMlevel) {
        registerWith(underlyingDividendTS_);
        registerWith(riskFreeTS_);
        registerWith(foreignRiskFreeTS_);
        registerWith(underlyingBlackVolTS_);
        registerWith(exchRateBlackVolTS_);
    }

    inline DayCounter QuantoTermStructure::dayCounter() const {
        return underlyingDividendTS_->dayCounter();
    }

    inline Calendar QuantoTermStructure::calendar() const {
        return underlyingDividendTS_->calendar();
    }

    inline Natural QuantoTermStructure::settlementDays() const {
        return underlyingDividendTS_->settlementDays();
    }

    inline const Date& QuantoTermStructure::referenceDate() const {
        return underlyingDividendTS_->referenceDate();
    }

    inline Date QuantoTermStructure::maxDate() const {
        Date maxDate = std::min(underlyingDividendTS_->maxDate(),
                                riskFreeTS_->maxDate());
        maxDate = std::min(maxDate, foreignRiskFreeTS_->maxDate());
        maxDate = std::min(maxDate, underlyingBlackVolTS_->maxDate());
        maxDate = std::min(maxDate, exchRateBlackVolTS_->maxDate());
        return maxDate;
    }

    inline Rate QuantoTermStructure::zeroYieldImpl(Time t) const {
        // warning: here it is assumed that all TS have the same daycount.
        //          It should be QL_REQUIREd
        return underlyingDividendTS_->zeroRate(t, Continuous, NoFrequency, true).rate()
            +            riskFreeTS_->zeroRate(t, Continuous, NoFrequency, true).rate()
            -     foreignRiskFreeTS_->zeroRate(t, Continuous, NoFrequency, true).rate()
            + underlyingExchRateCorrelation_
            * underlyingBlackVolTS_->blackVol(t, strike_, true)
            *   exchRateBlackVolTS_->blackVol(t, exchRateATMlevel_, true);
    }

}


#endif
