package org.apidesign.apifest08.currency;

import java.math.BigDecimal;

import java.util.Date;

import java.util.HashMap;

import java.util.Map;

/**

 * Exchange rate provider. Provides  exchange rate for two currencies (method {@link #getExchangeRate(ConvertorCurrency, ConvertorCurrency)} ).

 * <p>

 * Several method can be created to create <code>ExchangeRateProvider</code>:

 * <ul>

 * <li>{@link #createExchangeRateProvider() } - create <em>simple</em> exchange rate provider using fixed echange rate.

 * <li>{@link #createExchangeRateProvider(IExchangeRateEngine) } - create exchange rate provider using custom {@link IExchangeRateEngine}.

 * </ul>

 * <p>

 * Date dependend exchange rate to be implemented.

 * 

 * @author arnostvalicek

 */

public class ExchangeRateProvider {

    IExchangeRateEngine exrateEngine;

    /**

     * Simple constructor for <code>ExchangeRateProviderM</code> which can provide fixed exchange rate.

     * 

     * Describes conversion <em>from ONE</em> to <em>to ONE</em> currency.

     * 

     * @param fromValue From value. BigDecimal value, precision should be set to currency precision.

     * @param fromCurrency From currency.

     * @param toValue To value. BigDecimal value, precision should be set to currency precision.

     * @param toCurrency To currency.

     * @deprecated deprecated since task2. Use {@link #createExchangeRateProvider() } instead of this constructor.

     */

    public ExchangeRateProvider(BigDecimal fromValue, ConvertorCurrency fromCurrency, BigDecimal toValue, ConvertorCurrency toCurrency) {

        this.exrateEngine = FixedOneExchangeRateEngine.createEngine(fromValue, fromCurrency, toValue, toCurrency);

    }

    private ExchangeRateProvider() {

    }

    /**

     * Static method to create new exchange rate provider. This exchange rate provider does not contain

     * any exchange rates (this is difference to public constructor).

     * @return New <code>ExchangeRateProvider</code>

     */

    public static ExchangeRateProvider createExchangeRateProvider() {

        ExchangeRateProvider provider = new ExchangeRateProvider();

        provider.exrateEngine = FixedExchangeRateEngine.createEngine();

        return provider;

    }

    /**

     * Static method to create exchange rate provider which is using provided <code>IExchangeRateEngine</code>. This exchange rate provider is using

     * <code>IExchangeRateEngine</code> to get actual exchange rate.

     * @param exchangeRateEngine <code>IExchangeRateEngine</code> used to get exchange rate.

     * @return Returns instance of <code>ExchangeRateProvider</code>

     */

    public static ExchangeRateProvider createExchangeRateProvider(IExchangeRateEngine exchangeRateEngine) {

        ExchangeRateProvider provider = new ExchangeRateProvider();

        provider.exrateEngine = exchangeRateEngine;

        return provider;

    }

    /**

     * Add new exchange rate to <code></code> to this <em>simple</em> exchange rate provider.

     * <p>

     * Example of specifiing conversion rate: 100 SKK == 80 CZK:<br>

     * <code>addFixedCurencyRate(ConvertorCurrency.getInstance("SKK"), new BigDecimal(100), ConvertorCurrency.getInstance("CZK"),  new BigDecimal(80));</code>

     * <p>

     * This method may be used <em>only</em> when <code>ExchangeRateProvider</code> is created using {@link #createExchangeRateProvider() } - creating exchange rate provider without external <code>IExchangeRateEngine</code>.

     * 

     * @param fromCurrency Source currency.

     * @param fromValue Valye for from currency.

     * @param toCurrency Target currency.

     * @param toValue Value for target currency.

     * @throws IllegalStateException Throws exception when adding fixed currency rate to exchange rate provider which is not created using {@link #createExchangeRateProvider() }.

     */

    public synchronized void addFixedCurencyRate(ConvertorCurrency fromCurrency, BigDecimal fromValue, ConvertorCurrency toCurrency, BigDecimal toValue) {

        if (exrateEngine instanceof FixedExchangeRateEngine) {

            ((FixedExchangeRateEngine) exrateEngine).addFixedCurencyRate(fromCurrency, fromValue, toCurrency, toValue);

        } else {

            throw new IllegalStateException("Cuurency rate can be added only to ExchangeRateProvider created with FixedExchangeRateEngine - using method createExchangeRateProvider()");

        }

    }

    /**

     * Get fixed exange rate for currencies (from->to).

     * @return Returns exchange rate.

     * @deprecated deprecated since task2. Use {@link #getExchangeRate(ConvertorCurrency, ConvertorCurrency) }

     */

    public ExchangeRate getExchangeRate() {

        //works only for FixedExchangeRateEngine

        if (exrateEngine instanceof FixedOneExchangeRateEngine) {

            FixedOneExchangeRateEngine engine = (FixedOneExchangeRateEngine) exrateEngine;

            return new ExchangeRate(engine.getFromValue(), engine.getToValue());

        } else {

            throw new IllegalStateException("Method supported only for MinimalFixedExchangeRateEngine. This method is deprecated");

        }

    }

    /**

     * Get fixed exange rate for currencies (from->to).

     * @return Returns exchange rate or <code>null</code> if exchange rate not found.

     */

    public ExchangeRate getExchangeRate(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency) {

        return getExchangeRateImpl(fromCurrency, toCurrency);

    }

    /**

     * Get fixed exange rate for currencies (from->to) or reversed exchange rate (to->from).

     * @return Returns exchange rate or <code>null</code> if exchange rate not found.

     */

    public ExchangeRate getReversibleExchangeRate(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency) {

        ExchangeRate rate = getExchangeRateImpl(fromCurrency, toCurrency);

        if (rate == null) {

            ExchangeRate revertedRate = getExchangeRateImpl(toCurrency, fromCurrency);

            if (revertedRate != null) {

                rate = ExchangeRate.createRevertedRate(revertedRate);

            }

        }

        return rate;

    }

    /**

     * Get exchange rate for currencies (from->to) based on provided date.

     * @param date Date for which exchange rate should be provided.

     * @return Returns exchange rate 

     * @deprecated deprecated since task2. No real implementation in version2.

     */

    public ExchangeRate getExchangeRate(Date date) {

        //works only for FixedExchangeRateEngine

        if (exrateEngine instanceof FixedOneExchangeRateEngine) {

            FixedOneExchangeRateEngine engine = (FixedOneExchangeRateEngine) exrateEngine;

            return new ExchangeRate(engine.getFromValue(), engine.getToValue());

        } else {

            throw new IllegalStateException("Method supported only for FixedOneExchangeRateEngine. This method is deprecated");

        }

    }

    ConvertorCurrency getFromCurrency() {

        if (exrateEngine instanceof FixedOneExchangeRateEngine) {

            FixedOneExchangeRateEngine engine = (FixedOneExchangeRateEngine) exrateEngine;

            return engine.getFromCurrency();

        } else {

            throw new IllegalStateException("Method supported only for FixedOneExchangeRateEngine. This method is deprecated");

        }

    }

    ConvertorCurrency getToCurrency() {

        if (exrateEngine instanceof FixedOneExchangeRateEngine) {

            FixedOneExchangeRateEngine engine = (FixedOneExchangeRateEngine) exrateEngine;

            return engine.getToCurrency();

        } else {

            throw new IllegalStateException("Method supported only for FixedOneExchangeRateEngine. This method is deprecated");

        }

    }

    private ExchangeRate getExchangeRateImpl(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency) {

        ExchangeRate result = exrateEngine.getExchangeRate(fromCurrency, toCurrency);

        return result;

    }

    private static class FixedOneExchangeRateEngine implements IExchangeRateEngine {

        BigDecimal fromValue;

        ConvertorCurrency fromCurrency;

        BigDecimal toValue;

        ConvertorCurrency toCurrency;

        private FixedOneExchangeRateEngine(BigDecimal fromValue, ConvertorCurrency fromCurrency, BigDecimal toValue, ConvertorCurrency toCurrency) {

            this.fromValue = fromValue;

            this.toValue = toValue;

            this.fromCurrency = fromCurrency;

            this.toCurrency = toCurrency;

        }

        /**

         * Create IExchangeRateEngine conveting from <code>fromCurrency</code> to <code>toCurrency</code>

         * with echange rate <code>fromValue:toValue</code>

         * @param fromValue

         * @param fromCurrency

         * @param toValue

         * @param toCurrency

         * @return Returns instance of <code>FixedOneExchangeRateEngine</code>.

         */

        private static IExchangeRateEngine createEngine(BigDecimal fromValue, ConvertorCurrency fromCurrency, BigDecimal toValue, ConvertorCurrency toCurrency) {

            return new FixedOneExchangeRateEngine(fromValue, fromCurrency, toValue, toCurrency);

        }

        private BigDecimal getFromValue() {

            return fromValue;

        }

        private BigDecimal getToValue() {

            return toValue;

        }

        private ConvertorCurrency getFromCurrency() {

            return fromCurrency;

        }

        private ConvertorCurrency getToCurrency() {

            return toCurrency;

        }

        public ExchangeRate getExchangeRate(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency) {

            if (!fromCurrency.equals(this.fromCurrency)) {

                return null;

            }

            if (!toCurrency.equals(this.toCurrency)) {

                return null;

            }

            return new ExchangeRate(fromValue, toValue);

        }

    }

    /**

     * Exchange rate engine able to hold several fixed exchange rates.

     * 

     * @author arnostvalicek

     */

    private static class FixedExchangeRateEngine implements IExchangeRateEngine {

        private Map exchangeRateMap = new HashMap();

        private FixedExchangeRateEngine() {

        }

        /**

         * Create instance of <code>FixedExchangeRateEngine</code>.

         * @return Returns instance of <code>FixedExchangeRateEngine</code>.

         */

        public static IExchangeRateEngine createEngine() {

            return new FixedExchangeRateEngine();

        }

        public ExchangeRate getExchangeRate(ConvertorCurrency fromCurrency, ConvertorCurrency toCurrency) {

            Map map2 = (Map) exchangeRateMap.get(fromCurrency);

            if (map2 == null) {

                return null;

            }

            ExchangeRate result = (ExchangeRate) map2.get(toCurrency);

            return result;

        }

        @SuppressWarnings("unchecked")

        public synchronized void addFixedCurencyRate(ConvertorCurrency fromCurrency, BigDecimal fromValue, ConvertorCurrency toCurrency, BigDecimal toValue) {

            if (fromValue == null) {

                throw new NullPointerException("fromValue can't be null");

            }

            if (toValue == null) {

                throw new NullPointerException("toValue can't be null");

            }

            Map map2 = (Map) exchangeRateMap.get(fromCurrency);

            if (map2 == null) {

                map2 = new HashMap();

                exchangeRateMap.put(fromCurrency, map2);

            }

            ExchangeRate rate = new ExchangeRate(fromValue, toValue);

            map2.put(toCurrency, rate);

        }

    }

}