package org.apidesign.apifest08.currency;

import java.math.BigDecimal;

import java.util.Currency;

import java.util.Date;

/**

 * Create convertors using a flyweight to reduce the number of repetative creations of the same convertor.

 * 

 * @author D'Arcy Smith

 * @version 1.2

 */

public final class ConvertorFactory

{

    /** 

     * Prevent accidental construction.

     */

    private ConvertorFactory()

    {        

    }

    /**

     * Get the convertor for the specified currencies.  The currency name format

     * must be acceptable to java.util.Currency.getInstance(String)

     * 

     * @param a the currency to convert from.

     * @param aRate the exchange rate for a to b.

     * @param b the currency to convert to.

     * @param bRate the echante rate for b to a.

     * @return the convertor for the specified currencies.

     * @throws IllegalArgumentException if any of the arguments are null.

     */

    public static Convertor getConvertor(final String     a,

                                         final BigDecimal aRate,

                                         final String     b,

                                         final BigDecimal bRate)

    {

        final Currency  currencyA;

        final Currency  currencyB;

        final Convertor convertor;

        currencyA = Currency.getInstance(a);

        currencyB = Currency.getInstance(b);        

        convertor = getConvertor(currencyA, aRate, currencyB, bRate);

        return (convertor);

    }

    /**

     * Get the convertor for the specified currencies.

     * 

     * @param a the currency to convert from.

     * @param aRate the exchange rate for a to b.

     * @param b the currency to convert to.

     * @param bRate the echante rate for b to a.

     * @return the convertor for the specified currencies.

     * @throws IllegalArgumentException if either any of the arguments are null or if either rate <= 0.

     */

    public static Convertor getConvertor(final Currency   a,

                                         final BigDecimal aRate,

                                         final Currency   b,

                                         final BigDecimal bRate)

    {

        Convertor          convertor;

        final ExchangeRate rate;

        if(a == null)

        {

            throw new IllegalArgumentException("a cannot be null");

        }

        if(b == null)

        {

            throw new IllegalArgumentException("b cannot be null");

        }

        if(aRate == null)

        {

            throw new IllegalArgumentException("aRate cannot be null");

        }

        if(bRate == null)

        {

            throw new IllegalArgumentException("bRate cannot be null");

        }

        rate      = ExchangeRate.getExchangeRate(a, b, aRate, bRate);

        convertor = getConvertor(rate);

        return (convertor);

    }

    public static Convertor getConvertor(final ExchangeRate rate)

    {

        final ConvertorImpl convertor;

        if(rate == null)

        {

            throw new IllegalArgumentException("rate cannot be null");

        }

        convertor = new ConvertorImpl(rate);

        return (convertor);        

    }

    public static DatedConvertor getConvertor(final Date      from,

                                              final Date      till,

                                              final Convertor convertor)

    {

        final DateRange      range;

        final ExchangeRate   rate;

        final DatedConvertor datedConvertor;

        if(from == null)

        {

            throw new IllegalArgumentException("from cannot be null");

        }

        if(till == null)

        {

            throw new IllegalArgumentException("till cannot be null");

        }

        if(convertor == null)

        {

            throw new IllegalArgumentException("convertor cannot be null");

        }

        if(from.after(till))

        {

            throw new IllegalArgumentException(from + " cannot be after " + till);

        }

        if(convertor instanceof ExchangeRateConvertor)

        {

            rate = ((ExchangeRateConvertor)convertor).getExchangeRate();

        }

        else

        {

            throw new Error();

        }

        range          = new DateRange(from, till);

        datedConvertor = new DatedConvertorImpl(range, rate);

        return (datedConvertor);

    }

    /**

     * 

     * @param cs

     * @return

     */

    public static Convertor mergeConvertors(final Convertor ... cs)

    {

        Convertor convertor;

        int       dated;

        int       nonDated;

        dated    = 0;

        nonDated = 0;

        for(final Convertor c : cs)

        {

            if(c instanceof DatedConvertor)

            {

                dated++;

            }

            else

            {

                nonDated++;

            }

        }

        if(dated != 0 && nonDated != 0)

        {

            throw new IllegalArgumentException("cannot mix DatedConvertors and non-DatedConvertors");

        }

        if(dated != 0)

        {

            convertor = new DatedCompositeConvertorImpl(cs);

        }

        else

        {

            convertor = new CompositeConvertorImpl(cs);

        }

        return (convertor);

    }

}