package net.objectlab.kit.fxcalc;

import java.math.BigDecimal;
import java.util.Optional;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import net.objectlab.kit.util.BigDecimalUtil;

/**
 * Calculator responsible for generating a new cross FX Rate based on two relevant (sharing a cross currency) FX Rates; e.g. CHF/JPY based on USD/CHF and USD/JPY.
 * This calculator is able to handle all 'standard' cases where the market convention is different, e.g. GBP/CAD via USD/CAD and EUR/USD or inverted rates
 * if it is what you might have e.g. GBP/CAD via CAD/USD and EUR/USD.
 * @author Benoit Xhenseval
 */
public final class CrossRateCalculator {
    private static final Logger LOG = LoggerFactory.getLogger(CrossRateCalculator.class);

    private CrossRateCalculator() {
    }

    /**
     * Calculate the cross rate, use this only if required.
     * @param targetPair the currency pair we want Bid/Ask for
     * @param fx1 one rate involving either targetPair.ccy1 or targetPair.ccy2
     * @param fx2 one rate involving either targetPair.ccy1 or targetPair.ccy2
     * @param precision required in case we need to divide rates
     * @param ranking link to algorithm to determine if the targetPair will be market convention or not
     * @return a new instance of FxRate
     * @throws IllegalArgumentException if the 2 fx1 and fx2 do not share a common cross currency or either currencies in the targetPair
     */
    public static FxRate calculateCross(final CurrencyPair targetPair, final FxRate fx1, final FxRate fx2, final int precision,
            final int precisionForInverseFxRate, final MajorCurrencyRanking ranking, final int bidRounding, final int askRounding,
            CurrencyProvider currencyProvider) {
        final Optional<String> crossCcy = fx1.getCurrencyPair().findCommonCcy(fx2.getCurrencyPair());
        final String xCcy = crossCcy.orElseThrow(
                () -> new IllegalArgumentException("The 2 FXRates do not share a ccy " + fx1.getCurrencyPair() + " " + fx2.getCurrencyPair()));

        if (targetPair.containsCcy(crossCcy.get())) {
            throw new IllegalArgumentException("The target currency pair " + targetPair + " contains the common ccy " + crossCcy.get());
        }

        final String fx1Ccy1 = fx1.getCurrencyPair().getCcy1();
        final String fx2Ccy1 = fx2.getCurrencyPair().getCcy1();
        final String fx1Ccy2 = fx1.getCurrencyPair().getCcy2();
        final String fx2Ccy2 = fx2.getCurrencyPair().getCcy2();
        final boolean shouldDivide = fx1Ccy1.equals(xCcy) && fx2Ccy1.equals(xCcy) || fx1Ccy2.equals(xCcy) && fx2Ccy2.equals(xCcy); // what if it i
        // both ccy2?

        BigDecimal bid;
        BigDecimal ask;

        if (shouldDivide) {
            final FxRate numeratorFx = targetPair.getCcy1().equals(fx2Ccy2) || targetPair.getCcy1().equals(fx1Ccy1) ? fx1 : fx2;
            final FxRate denominatorFx = numeratorFx == fx1 ? fx2 : fx1;
            LOG.debug("CALC {} / {}", numeratorFx, denominatorFx);

            bid = BigDecimalUtil.divide(precision, numeratorFx.getBid(), denominatorFx.getAsk(), bidRounding);
            ask = BigDecimalUtil.divide(precision, numeratorFx.getAsk(), denominatorFx.getBid(), askRounding);
        } else {
            final boolean inverse = targetPair.getCcy1().equals(fx2Ccy2) || targetPair.getCcy1().equals(fx1Ccy2);
            LOG.debug("CALC {} x {}", fx1, fx2);
            if (inverse) {
                ask = BigDecimalUtil.setScale(
                        BigDecimalUtil.inverse(BigDecimalUtil.multiply(fx1.getBid(), fx2.getBid()), precisionForInverseFxRate, bidRounding),
                        precision);
                bid = BigDecimalUtil.setScale(
                        BigDecimalUtil.inverse(BigDecimalUtil.multiply(fx1.getAsk(), fx2.getAsk()), precisionForInverseFxRate, askRounding),
                        precision);
            } else {
                bid = BigDecimalUtil.setScale(BigDecimalUtil.multiply(fx1.getBid(), fx2.getBid()), precision);
                ask = BigDecimalUtil.setScale(BigDecimalUtil.multiply(fx1.getAsk(), fx2.getAsk()), precision);
            }
        }
        final FxRateImpl crossRate = new FxRateImpl(targetPair, xCcy, ranking.isMarketConvention(targetPair), bid, ask, currencyProvider);
        LOG.debug("X RATE {}", crossRate);
        LOG.debug(crossRate.getDescription());
        return crossRate;
    }
}