
/*
 Copyright (C) 2002, 2003 Ferdinando Ametrano
 Copyright (C) 2003 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 http://quantlib.org/html/license.html

 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 blackvariancecurve.hpp
    \brief Black volatility curve modelled as variance curve
*/

#ifndef quantlib_blackvariancecurve_hpp
#define quantlib_blackvariancecurve_hpp

#include <ql/voltermstructure.hpp>
#include <ql/Math/interpolation.hpp>
#include <ql/DayCounters/actual365.hpp>

namespace QuantLib {

    //! Black volatility curve modelled as variance curve
    /*! This class calculates time-dependent Black volatilities using
        as input a vector of (ATM) Black volatilities observed in the
        market.

        The calculation is performed interpolating on the variance curve.
        Linear interpolation is used as default; this can be changed
        by the setInterpolation() method.
            
        For strike dependence, see BlackVarianceSurface.

        \todo check time extrapolation

    */
    class BlackVarianceCurve : public BlackVarianceTermStructure,
                               public Observer {
      public:
        BlackVarianceCurve(const Date& referenceDate,
                           const std::vector<Date>& dates,
                           const std::vector<double>& blackVolCurve,
                           const DayCounter& dayCounter = Actual365());
        //! \name BlackVolTermStructure interface
        //@{
        Date referenceDate() const;
        DayCounter dayCounter() const;
        Date maxDate() const;
        //@}
        //! \name Modifiers
        //@{
        template <class Traits>
        #if defined(QL_PATCH_MICROSOFT)
        void setInterpolation(const Traits&) {
        #else
        void setInterpolation() {
        #endif
            varianceCurve_ = 
                Traits::make_interpolation(times_.begin(), times_.end(),
                                           variances_.begin());
            notifyObservers();
        }
        //@}
        //! \name Observer interface
        //@{
        void update();
        //@}
        //! \name Visitability
        //@{
        virtual void accept(AcyclicVisitor&);
        //@}
        protected:
        virtual double blackVarianceImpl(Time t, double,
                                         bool extrapolate = false) const;
        private:
        Date referenceDate_;
        DayCounter dayCounter_;
        Date maxDate_;
        std::vector<Time> times_;
        std::vector<double> variances_;
        Interpolation varianceCurve_;
    };


    // inline definitions

    inline Date BlackVarianceCurve::referenceDate() const { 
        return referenceDate_; 
    }

    inline DayCounter BlackVarianceCurve::dayCounter() const { 
        return dayCounter_; 
    }

    inline Date BlackVarianceCurve::maxDate() const { 
        return maxDate_; 
    }

    inline void BlackVarianceCurve::update() {
        notifyObservers();
    }

    inline void BlackVarianceCurve::accept(AcyclicVisitor& v) {
        Visitor<BlackVarianceCurve>* v1 = 
            dynamic_cast<Visitor<BlackVarianceCurve>*>(&v);
        if (v1 != 0)
            v1->visit(*this);
        else
            BlackVarianceTermStructure::accept(v);
    }

}


#endif
