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

/*
 Copyright (C) 2007, 2009 Chris Kenyon

 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
 <http://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 inflationtermstructure.hpp
    \brief Base classes for inflation term structures.
*/

#ifndef quantlib_inflation_termstructure_hpp
#define quantlib_inflation_termstructure_hpp

#include <ql/termstructures/yieldtermstructure.hpp>
#include <ql/termstructures/inflation/seasonality.hpp>

namespace QuantLib {

    class InflationIndex;

    //! Interface for inflation term structures.
    /*! \ingroup inflationtermstructures */
    class InflationTermStructure : public TermStructure {
      public:
        //! \name Constructors
        //@{
        InflationTermStructure(Date baseDate,
                               Frequency frequency,
                               const DayCounter& dayCounter = DayCounter(),
                               ext::shared_ptr<Seasonality> seasonality = {},
                               Rate baseRate = Null<Rate>());

        InflationTermStructure(const Date& referenceDate,
                               Date baseDate,
                               Frequency frequency,
                               const DayCounter& dayCounter = DayCounter(),
                               ext::shared_ptr<Seasonality> seasonality = {},
                               Rate baseRate = Null<Rate>());

        InflationTermStructure(Natural settlementDays,
                               const Calendar& calendar,
                               Date baseDate,
                               Frequency frequency,
                               const DayCounter& dayCounter = DayCounter(),
                               ext::shared_ptr<Seasonality> seasonality = {},
                               Rate baseRate = Null<Rate>());

        /*! \deprecated Use another overload and pass the base date directly
                        instead of using a lag.
                        Deprecated in version 1.34.
        */
        QL_DEPRECATED
        InflationTermStructure(Rate baseRate,
                               const Period& observationLag,
                               Frequency frequency,
                               const DayCounter& dayCounter = DayCounter(),
                               ext::shared_ptr<Seasonality> seasonality = {});

        /*! \deprecated Use another overload and pass the base date directly
                        instead of using a lag.
                        Deprecated in version 1.34.
        */
        QL_DEPRECATED
        InflationTermStructure(const Date& referenceDate,
                               Rate baseRate,
                               const Period& observationLag,
                               Frequency frequency,
                               const Calendar& calendar = Calendar(),
                               const DayCounter& dayCounter = DayCounter(),
                               ext::shared_ptr<Seasonality> seasonality = {});

        /*! \deprecated Use another overload and pass the base date directly
                        instead of using a lag.
                        Deprecated in version 1.34.
        */
        QL_DEPRECATED
        InflationTermStructure(Natural settlementDays,
                               const Calendar& calendar,
                               Rate baseRate,
                               const Period& observationLag,
                               Frequency frequency,
                               const DayCounter& dayCounter = DayCounter(),
                               ext::shared_ptr<Seasonality> seasonality = {});
        //@}

        //! \name Inflation interface
        //@{
        virtual Period observationLag() const;
        virtual Frequency frequency() const;
        virtual Rate baseRate() const;

        //! minimum (base) date
        /*! The last date for which we have information.

            When not set directly (the recommended option), it is
            calculated base on an observation lag relative to today.
        */
        virtual Date baseDate() const;

        /*! This can be used temporarily to check whether the term structure
            was created using one of the new constructors taking a base date
            or one of the deprecated ones taking an observation lag.
        */
        bool hasExplicitBaseDate() const {
            return hasExplicitBaseDate_;
        }
        //@}

        //! \name Seasonality
        //@{
        /*! \deprecated Use the overload taking a pointer and pass an empty one to remove seasonality.
                        Deprecated in version 1.34.
        */
        [[deprecated("Use the overload taking a pointer and pass an empty one to remove seasonality.")]]
        void setSeasonality() { setSeasonality({}); }
        void setSeasonality(const ext::shared_ptr<Seasonality>& seasonality);
        ext::shared_ptr<Seasonality> seasonality() const;
        bool hasSeasonality() const;
        //@}

      protected:
        /*! \deprecated Do not use; set baseRate_ directly if needed.
                        Deprecated in version 1.34.
        */
        [[deprecated("Do not use; set baseRate_ directly if needed.")]]
        virtual void setBaseRate(const Rate& r) { baseRate_ = r; }

        // range-checking
        void checkRange(const Date&,
                        bool extrapolate) const;
        void checkRange(Time t,
                        bool extrapolate) const;

        ext::shared_ptr<Seasonality> seasonality_;
        Period observationLag_;
        Frequency frequency_;
        mutable Rate baseRate_;

      private:
        Date baseDate_;
        bool hasExplicitBaseDate_;
    };

    //! Interface for zero inflation term structures.
    class ZeroInflationTermStructure : public InflationTermStructure {
      public:
        //! \name Constructors
        //@{
        ZeroInflationTermStructure(Date baseDate,
                                   Frequency frequency,
                                   const DayCounter& dayCounter,
                                   const ext::shared_ptr<Seasonality>& seasonality = {});

        ZeroInflationTermStructure(const Date& referenceDate,
                                   Date baseDate,
                                   Frequency frequency,
                                   const DayCounter& dayCounter,
                                   const ext::shared_ptr<Seasonality>& seasonality = {});

        ZeroInflationTermStructure(Natural settlementDays,
                                   const Calendar& calendar,
                                   Date baseDate,
                                   Frequency frequency,
                                   const DayCounter& dayCounter,
                                   const ext::shared_ptr<Seasonality>& seasonality = {});

        /*! \deprecated Use another overload and pass the base date directly
                        instead of using a lag. A base rate should not be needed.
                        Deprecated in version 1.34.
        */
        QL_DEPRECATED
        ZeroInflationTermStructure(const DayCounter& dayCounter,
                                   Rate baseZeroRate,
                                   const Period& lag,
                                   Frequency frequency,
                                   const ext::shared_ptr<Seasonality>& seasonality = {});

        /*! \deprecated Use another overload and pass the base date directly
                        instead of using a lag. A base rate should not be needed.
                        Deprecated in version 1.34.
        */
        QL_DEPRECATED
        ZeroInflationTermStructure(const Date& referenceDate,
                                   const Calendar& calendar,
                                   const DayCounter& dayCounter,
                                   Rate baseZeroRate,
                                   const Period& lag,
                                   Frequency frequency,
                                   const ext::shared_ptr<Seasonality>& seasonality = {});

        /*! \deprecated Use another overload and pass the base date directly
                        instead of using a lag. A base rate should not be needed.
                        Deprecated in version 1.34.
        */
        QL_DEPRECATED
        ZeroInflationTermStructure(Natural settlementDays,
                                   const Calendar& calendar,
                                   const DayCounter& dayCounter,
                                   Rate baseZeroRate,
                                   const Period& lag,
                                   Frequency frequency,
                                   const ext::shared_ptr<Seasonality>& seasonality = {});
        //@}

        //! \name Inspectors
        //@{
        //! zero-coupon inflation rate.
        /*! Essentially the fair rate for a zero-coupon inflation swap
            (by definition), i.e. the zero term structure uses yearly
            compounding, which is assumed for ZCIIS instrument quotes.

            \note by default you get the same as lag and interpolation
            as the term structure.
            If you want to get predictions of RPI/CPI/etc then use an
            index.
        */
        Rate zeroRate(const Date& d, const Period& instObsLag = Period(-1,Days),
                      bool forceLinearInterpolation = false,
                      bool extrapolate = false) const;
        //! zero-coupon inflation rate.
        /*! \warning Since inflation is highly linked to dates (lags,
                     interpolation, months for seasonality, etc) this
                     method cannot account for all effects.  If you
                     call it, You'll have to manage lag, seasonality
                     etc. yourself.
        */
        Rate zeroRate(Time t,
                      bool extrapolate = false) const;
        //@}
      protected:
        //! to be defined in derived classes
        virtual Rate zeroRateImpl(Time t) const = 0;
    };


    //! Base class for year-on-year inflation term structures.
    class YoYInflationTermStructure : public InflationTermStructure {
      public:
        //! \name Constructors
        //@{
        YoYInflationTermStructure(Date baseDate,
                                  Rate baseYoYRate,
                                  Frequency frequency,
                                  bool indexIsInterpolated,
                                  const DayCounter& dayCounter,
                                  const ext::shared_ptr<Seasonality>& seasonality = {});

        YoYInflationTermStructure(const Date& referenceDate,
                                  Date baseDate,
                                  Rate baseYoYRate,
                                  Frequency frequency,
                                  bool indexIsInterpolated,
                                  const DayCounter& dayCounter,
                                  const ext::shared_ptr<Seasonality>& seasonality = {});

        YoYInflationTermStructure(Natural settlementDays,
                                  const Calendar& calendar,
                                  Date baseDate,
                                  Rate baseYoYRate,
                                  Frequency frequency,
                                  bool indexIsInterpolated,
                                  const DayCounter& dayCounter,
                                  const ext::shared_ptr<Seasonality>& seasonality = {});

        /*! \deprecated Use another overload and pass the base date directly
                        instead of using a lag.
                        Deprecated in version 1.34.
        */
        QL_DEPRECATED
        YoYInflationTermStructure(const DayCounter& dayCounter,
                                  Rate baseYoYRate,
                                  const Period& lag,
                                  Frequency frequency,
                                  bool indexIsInterpolated,
                                  const ext::shared_ptr<Seasonality>& seasonality = {});

        /*! \deprecated Use another overload and pass the base date directly
                        instead of using a lag.
                        Deprecated in version 1.34.
        */
        QL_DEPRECATED
        YoYInflationTermStructure(const Date& referenceDate,
                                  const Calendar& calendar,
                                  const DayCounter& dayCounter,
                                  Rate baseYoYRate,
                                  const Period& lag,
                                  Frequency frequency,
                                  bool indexIsInterpolated,
                                  const ext::shared_ptr<Seasonality>& seasonality = {});

        /*! \deprecated Use another overload and pass the base date directly
                        instead of using a lag.
                        Deprecated in version 1.34.
        */
        QL_DEPRECATED
        YoYInflationTermStructure(Natural settlementDays,
                                  const Calendar& calendar,
                                  const DayCounter& dayCounter,
                                  Rate baseYoYRate,
                                  const Period& lag,
                                  Frequency frequency,
                                  bool indexIsInterpolated,
                                  const ext::shared_ptr<Seasonality>& seasonality = {});
        //@}

        //! \name Inspectors
        //@{
        //! year-on-year inflation rate.
        /*! The forceLinearInterpolation parameter is relative to the
            frequency of the TS.

            \note this is not the year-on-year swap (YYIIS) rate.
        */
        Rate yoyRate(const Date& d, const Period& instObsLag = Period(-1,Days),
                     bool forceLinearInterpolation = false,
                     bool extrapolate = false) const;
        //! year-on-year inflation rate.
        /*! \warning Since inflation is highly linked to dates (lags,
                     interpolation, months for seasonality, etc) this
                     method cannot account for all effects.  If you
                     call it, You'll have to manage lag, seasonality
                     etc. yourself.
        */
        Rate yoyRate(Time t,
                     bool extrapolate = false) const;
        //@}

        virtual bool indexIsInterpolated() const;
      protected:
        //! to be defined in derived classes
        virtual Rate yoyRateImpl(Time time) const = 0;
      private:
        bool indexIsInterpolated_;
    };


    //! utility function giving the inflation period for a given date
    std::pair<Date,Date> inflationPeriod(const Date&,
                                         Frequency);

    //! utility function giving the time between two dates depending on
    //! index frequency and interpolation, and a day counter
    Time inflationYearFraction(Frequency ,
                               bool indexIsInterpolated,
                               const DayCounter&,
                               const Date&, const Date&);


    // inline

    inline Period InflationTermStructure::observationLag() const {
        return observationLag_;
    }

    inline Frequency InflationTermStructure::frequency() const {
        return frequency_;
    }

    inline Rate InflationTermStructure::baseRate() const {
        QL_REQUIRE(baseRate_ != Null<Real>(), "base rate not available");
        return baseRate_;
    }

    inline ext::shared_ptr<Seasonality> InflationTermStructure::seasonality() const {
        return seasonality_;
    }

    inline bool InflationTermStructure::hasSeasonality() const {
        return static_cast<bool>(seasonality_);
    }

    inline bool YoYInflationTermStructure::indexIsInterpolated() const {
        return indexIsInterpolated_;
    }

}

#endif
