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

/*

 Copyright (C) 2005, 2006 Theo Boafo

 Copyright (C) 2006, 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/bond/discretizedconvertible.hpp>

#include <ql/math/comparison.hpp>

#include <ql/processes/blackscholesprocess.hpp>

#include <utility>

namespace QuantLib {

    DiscretizedConvertible::DiscretizedConvertible(

        ConvertibleBond::arguments args,

        ext::shared_ptr<GeneralizedBlackScholesProcess> process,

        const DividendSchedule& dividends,

        Handle<Quote> creditSpread,

        const TimeGrid& grid)

    : arguments_(std::move(args)), process_(std::move(process)),

      creditSpread_(std::move(creditSpread)) {

        for (const auto& dividend : dividends) {

            if (!dividend->hasOccurred(arguments_.settlementDate, false)) {

                dividends_.push_back(dividend);

                dividendDates_.push_back(dividend->date());

            }

        }

        dividendValues_ = Array(dividends_.size(), 0.0);

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

            dividendValues_[i] =

                dividends_[i]->amount() *

                process_->riskFreeRate()->discount(dividendDates_[i]);

        }

        DayCounter dayCounter = process_->riskFreeRate()->dayCounter();

        Date bondSettlement = arguments_.settlementDate;

        stoppingTimes_.resize(arguments_.exercise->dates().size());

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

            stoppingTimes_[i] =

                dayCounter.yearFraction(bondSettlement,

                                        arguments_.exercise->date(i));

        callabilityTimes_.resize(arguments_.callabilityDates.size());

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

            callabilityTimes_[i] =

                dayCounter.yearFraction(bondSettlement,

                                        arguments_.callabilityDates[i]);

        couponTimes_.clear();

        couponAmounts_.clear();

        for (Size i = 0; i < arguments_.cashflows.size() - 1; ++i) {

            if (!arguments_.cashflows[i]->hasOccurred(bondSettlement, false)) {

                couponTimes_.push_back(dayCounter.yearFraction(bondSettlement,

                                                               arguments_.cashflows[i]->date()));

                couponAmounts_.push_back(arguments_.cashflows[i]->amount());

            }

        }

        dividendTimes_.resize(dividendDates_.size());

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

            dividendTimes_[i] =

                dayCounter.yearFraction(bondSettlement,

                                        dividendDates_[i]);

        if (!grid.empty()) {

            // adjust times to grid

            for (Real& stoppingTime : stoppingTimes_)

                stoppingTime = grid.closestTime(stoppingTime);

            for (Real& couponTime : couponTimes_)

                couponTime = grid.closestTime(couponTime);

            for (Real& callabilityTime : callabilityTimes_)

                callabilityTime = grid.closestTime(callabilityTime);

            for (Real& dividendTime : dividendTimes_)

                dividendTime = grid.closestTime(dividendTime);

        }

    }

    void DiscretizedConvertible::reset(Size size) {

        // Set to bond redemption values

        values_ = Array(size, arguments_.redemption);

        // coupon amounts should be added when adjusting

        // values_ = Array(size, arguments_.cashFlows.back()->amount());

        conversionProbability_ = Array(size, 0.0);

        spreadAdjustedRate_ = Array(size, 0.0);

        DayCounter rfdc  = process_->riskFreeRate()->dayCounter();

        // this takes care of convertibility and conversion probabilities

        adjustValues();

        Real creditSpread = creditSpread_->value();

        Date exercise = arguments_.exercise->lastDate();

        Rate riskFreeRate =

            process_->riskFreeRate()->zeroRate(exercise, rfdc,

                                               Continuous, NoFrequency);

        // Calculate blended discount rate to be used on roll back.

        for (Size j=0; j<values_.size(); j++) {

           spreadAdjustedRate_[j] =

               conversionProbability_[j] * riskFreeRate +

               (1-conversionProbability_[j])*(riskFreeRate + creditSpread);

        }

    }

    void DiscretizedConvertible::postAdjustValuesImpl() {

        bool convertible = false;

        switch (arguments_.exercise->type()) {

          case Exercise::American:

            if ((time() <= stoppingTimes_[1] || isOnTime(stoppingTimes_[1])) &&

                (time() >= stoppingTimes_[0] || isOnTime(stoppingTimes_[0])))

                convertible = true;

            break;

          case Exercise::European:

            if (isOnTime(stoppingTimes_[0]))

                convertible = true;

            break;

          case Exercise::Bermudan:

              for (Real stoppingTime : stoppingTimes_) {

                  if (isOnTime(stoppingTime))

                      convertible = true;

              }

            break;

          default:

            QL_FAIL("invalid option type");

        }

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

            if (isOnTime(callabilityTimes_[i]))

                applyCallability(i,convertible);

        }

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

            if (isOnTime(couponTimes_[i]))

                addCoupon(i);

        }

        if (convertible)

            applyConvertibility();

    }

    void DiscretizedConvertible::applyConvertibility() {

        Array grid = adjustedGrid();

        for (Size j=0; j<values_.size(); j++) {

            Real payoff = arguments_.conversionRatio*grid[j];

            if (values_[j] <= payoff) {

                values_[j] = payoff;

                conversionProbability_[j] = 1.0;

            }

        }

    }

    void DiscretizedConvertible::applyCallability(Size i, bool convertible) {

        Size j;

        Array grid = adjustedGrid();

        switch (arguments_.callabilityTypes[i]) {

          case Callability::Call:

            if (arguments_.callabilityTriggers[i] != Null<Real>()) {

                Real conversionValue =

                    arguments_.redemption/arguments_.conversionRatio;

                Real trigger =

                    conversionValue*arguments_.callabilityTriggers[i];

                for (j=0; j<values_.size(); j++) {

                    // the callability is conditioned by the trigger...

                    if (grid[j] >= trigger) {

                        // ...and might trigger conversion

                        values_[j] =

                            std::min(std::max(

                                          arguments_.callabilityPrices[i],

                                          arguments_.conversionRatio*grid[j]),

                                     values_[j]);

                    }

                }

            } else if (convertible) {

                for (j=0; j<values_.size(); j++) {

                    // exercising the callability might trigger conversion

                    values_[j] =

                        std::min(std::max(arguments_.callabilityPrices[i],

                                          arguments_.conversionRatio*grid[j]),

                                 values_[j]);

                }

            } else {

                for (j=0; j<values_.size(); j++) {

                    values_[j] = std::min(arguments_.callabilityPrices[i],

                                          values_[j]);

                }

            }

            break;

          case Callability::Put:

            for (j=0; j<values_.size(); j++) {

                values_[j] = std::max(values_[j],

                                      arguments_.callabilityPrices[i]);

            }

            break;

          default:

            QL_FAIL("unknown callability type");

        }

    }

    void DiscretizedConvertible::addCoupon(Size i) {

        values_ += couponAmounts_[i];

    }

    Array DiscretizedConvertible::adjustedGrid() const {

        Time t = time();

        Array grid = method()->grid(t);

        // add back all dividend amounts in the future

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

            Time dividendTime = dividendTimes_[i];

            if (dividendTime >= t || close(dividendTime,t)) {

                const ext::shared_ptr<Dividend>& d = dividends_[i];

                DiscountFactor dividendDiscount =

                    process_->riskFreeRate()->discount(dividendTime) /

                    process_->riskFreeRate()->discount(t);

                for (Real& j : grid)

                    j += d->amount(j) * dividendDiscount;

            }

        }

        return grid;

    }

}