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

/*

 Copyright (C) 2026 Zain Mughal

 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/instruments/makemultipleresetsswap.hpp>

#include <ql/instruments/simplifynotificationgraph.hpp>

#include <ql/termstructures/yield/multipleresetsswaphelper.hpp>

#include <ql/utilities/null_deleter.hpp>

namespace QuantLib {

    MultipleResetsSwapRateHelper::MultipleResetsSwapRateHelper(

        Natural settlementDays,

        const Period& tenor,

        const std::variant<Rate, Handle<Quote>>& fixedRate,

        const ext::shared_ptr<IborIndex>& iborIndex,

        Size resetsPerCoupon,

        Handle<YieldTermStructure> discountingCurve,

        RateAveraging::Type averagingMethod,

        Spread spread,

        Frequency fixedFrequency,

        const DayCounter& fixedDayCount,

        BusinessDayConvention fixedConvention)

    : RelativeDateRateHelper(fixedRate), settlementDays_(settlementDays), tenor_(tenor),

      resetsPerCoupon_(resetsPerCoupon), averagingMethod_(averagingMethod), spread_(spread),

      fixedFrequency_(fixedFrequency),

      fixedDayCount_(!fixedDayCount.empty() ? fixedDayCount : iborIndex->dayCounter()),

      fixedConvention_(fixedConvention), discountHandle_(std::move(discountingCurve)) {

        // Clone the index so it forwards rates from termStructureHandle_,

        // but don't register the clone as an observer of termStructureHandle_

        // (that would interfere with bootstrapping).

        iborIndex_ = ext::dynamic_pointer_cast<IborIndex>(iborIndex->clone(termStructureHandle_));

        iborIndex_->unregisterWith(termStructureHandle_);

        registerWith(iborIndex_);

        registerWith(discountHandle_);

        initializeDates();

    }

    void MultipleResetsSwapRateHelper::initializeDates() {

        swap_ = MakeMultipleResetsSwap(tenor_, iborIndex_, resetsPerCoupon_)

                    .withFixedRate(0.0)

                    .withSettlementDays(settlementDays_)

                    .withFixedLegFrequency(fixedFrequency_)

                    .withFixedLegDayCount(fixedDayCount_)

                    .withFixedLegConvention(fixedConvention_)

                    .withFloatingLegSpread(spread_)

                    .withAveragingMethod(averagingMethod_)

                    .withDiscountingTermStructure(discountRelinkableHandle_);

        simplifyNotificationGraph(*swap_, true);

        earliestDate_ = swap_->startDate();

        latestRelevantDate_ = latestDate_ =

            std::max(swap_->fixedLeg().back()->date(), swap_->floatingLeg().back()->date());

    }

    void MultipleResetsSwapRateHelper::setTermStructure(YieldTermStructure* t) {

        bool observer = false;

        ext::shared_ptr<YieldTermStructure> temp(t, null_deleter());

        termStructureHandle_.linkTo(temp, observer);

        if (discountHandle_.empty())

            discountRelinkableHandle_.linkTo(temp, observer);

        else

            discountRelinkableHandle_.linkTo(*discountHandle_, observer);

        RelativeDateRateHelper::setTermStructure(t);

    }

    Real MultipleResetsSwapRateHelper::impliedQuote() const {

        QL_REQUIRE(termStructure_ != nullptr, "term structure not set");

        swap_->deepUpdate();

        return swap_->fairRate();

    }

    void MultipleResetsSwapRateHelper::accept(AcyclicVisitor& v) {

        auto* v1 = dynamic_cast<Visitor<MultipleResetsSwapRateHelper>*>(&v);

        if (v1 != nullptr)

            v1->visit(*this);

        else

            RateHelper::accept(v);

    }

}