/*
 * CREDIT SUISSE IS WILLING TO LICENSE THIS SPECIFICATION TO YOU ONLY UPON THE
 * CONDITION THAT YOU ACCEPT ALL OF THE TERMS CONTAINED IN THIS AGREEMENT.
 * PLEASE READ THE TERMS AND CONDITIONS OF THIS AGREEMENT CAREFULLY. BY
 * DOWNLOADING THIS SPECIFICATION, YOU ACCEPT THE TERMS AND CONDITIONS OF THE
 * AGREEMENT. IF YOU ARE NOT WILLING TO BE BOUND BY IT, SELECT THE "DECLINE"
 * BUTTON AT THE BOTTOM OF THIS PAGE. Specification: JSR-354 Money and Currency
 * API ("Specification") Copyright (c) 2012-2013, Credit Suisse All rights
 * reserved.
 */
package javax.money.convert;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
import java.util.ServiceLoader;
import java.util.logging.Logger;

import javax.money.CurrencyUnit;
import javax.money.Monetary;
import javax.money.MonetaryException;
import javax.money.spi.Bootstrap;
import javax.money.spi.MonetaryConversionsSingletonSpi;

This singleton defines access to the exchange and currency conversion logic of JavaMoney. It allows to evaluate the currently available exchange rate type instances and provides access to the corresponding ExchangeRateProvider and CurrencyConversion instances. 

This class is thread safe.
 This class is designed to support also contextual behaviour, e.g. in Java EE containers each application may provide its own ExchangeRateProvider instances, e.g. by registering them as CDI beans. An EE container can register an according MonetaryConversionsSingletonSpi that manages the different application contexts transparently. In a SE environment this class is expected to behave like an ordinary singleton, loading its SPIs e.g. from the JDK ServiceLoader or an alternate component and service provider. 
 This class is thread-safe. Hereby it is important to know that it delegates to the registered MonetaryConversionsSingletonSpi SPI, which also is required to be thread-safe. 
Author:
Anatole Tresch, Werner Keil/**
 * This singleton defines access to the exchange and currency conversion logic
 * of JavaMoney. It allows to evaluate the currently available exchange rate
 * type instances and provides access to the corresponding
 * {@link ExchangeRateProvider} and {@link javax.money.convert.CurrencyConversion} instances.
 * <p>
 * This class is thread safe.
 * <p>
 * This class is designed to support also contextual behaviour, e.g. in Java EE
 * containers each application may provide its own {@link ExchangeRateProvider}
 * instances, e.g. by registering them as CDI beans. An EE container can
 * register an according {@link javax.money.spi.MonetaryConversionsSingletonSpi} that manages the
 * different application contexts transparently. In a SE environment this class
 * is expected to behave like an ordinary singleton, loading its SPIs e.g. from the
 * JDK {@link ServiceLoader} or an alternate component and service provider.
 * <p>
 * This class is thread-safe. Hereby it is important to know that it delegates
 * to the registered {@link javax.money.spi.MonetaryConversionsSingletonSpi} SPI, which also is required
 * to be thread-safe.
 *
 * @author Anatole Tresch
 * @author Werner Keil
 */
public final class MonetaryConversions{

    
The SPI currently active, use ServiceLoader to register an alternate implementation. /**
     * The SPI currently active, use {@link ServiceLoader} to register an
     * alternate implementation.
     */
    private static MonetaryConversionsSingletonSpi getMonetaryConversionsSpi() {
        return Optional.ofNullable(Bootstrap.getService(MonetaryConversionsSingletonSpi.class))
                .orElseThrow(() -> new MonetaryException("No MonetaryConversionsSingletonSpi " +
                        "loaded, " +
                        "query functionality is not " +
                        "available."));
    }

    
Private singleton constructor.
/**
     * Private singleton constructor.
     */
    private MonetaryConversions(){
    }

    
Access an instance of CurrencyConversion for the given providers. Use getConversionProviderNames() to check, which are available. 
Params:
termCurrency – the terminating or target currency, not null
providers –    Additional providers, for building a provider chain
Throws:
IllegalArgumentException – if no such ExchangeRateProvider is available.
Returns:
the exchange rate type if this instance./**
     * Access an instance of {@link CurrencyConversion} for the given providers.
     * Use {@link #getConversionProviderNames()} to check, which are available.
     *
     * @param termCurrency the terminating or target currency, not {@code null}
     * @param providers    Additional providers, for building a provider chain
     * @return the exchange rate type if this instance.
     * @throws IllegalArgumentException if no such {@link ExchangeRateProvider} is available.
     */
    public static CurrencyConversion getConversion(CurrencyUnit termCurrency, String... providers){
        Objects.requireNonNull(providers);
        Objects.requireNonNull(termCurrency);
        if(providers.length == 0){
            return getMonetaryConversionsSpi().getConversion(
                    ConversionQueryBuilder.of().setTermCurrency(termCurrency).setProviderNames(getDefaultConversionProviderChain())
                            .build());
        }
        return getMonetaryConversionsSpi().getConversion(
                ConversionQueryBuilder.of().setTermCurrency(termCurrency).setProviderNames(providers).build());
    }

    
Access an instance of CurrencyConversion for the given providers. Use getConversionProviderNames()} to check, which are available. 
Params:
termCurrencyCode – the terminating or target currency code, not null
providers –        Additional providers, for building a provider chain
Throws:
MonetaryException – if no such ExchangeRateProvider is available or if no CurrencyUnit was matching the given currency code.
Returns:
the exchange rate type if this instance./**
     * Access an instance of {@link CurrencyConversion} for the given providers.
     * Use {@link #getConversionProviderNames()}} to check, which are available.
     *
     * @param termCurrencyCode the terminating or target currency code, not {@code null}
     * @param providers        Additional providers, for building a provider chain
     * @return the exchange rate type if this instance.
     * @throws MonetaryException if no such {@link ExchangeRateProvider} is available or if no {@link CurrencyUnit} was
     *                           matching the given currency code.
     */
    public static CurrencyConversion getConversion(String termCurrencyCode, String... providers){
        Objects.requireNonNull(termCurrencyCode, "Term currency code may not be null");
        return getConversion(Monetary.getCurrency(termCurrencyCode), providers);
    }

    
Access an instance of CurrencyConversion for the given providers. Use getConversionProviderNames()} to check, which are available. 
Params:
conversionQuery – The ConversionQuery required, not null
Throws:
IllegalArgumentException – if the query defines ExchangeRateProviders that are not available.
Returns:
the CurrencyConversion instance matching./**
     * Access an instance of {@link CurrencyConversion} for the given providers.
     * Use {@link #getConversionProviderNames()}} to check, which are available.
     *
     * @param conversionQuery The {@link ConversionQuery} required, not {@code null}
     * @return the {@link CurrencyConversion}  instance matching.
     * @throws IllegalArgumentException if the query defines {@link ExchangeRateProvider}s that are not available.
     */
    public static CurrencyConversion getConversion(ConversionQuery conversionQuery){
        return getMonetaryConversionsSpi().getConversion(conversionQuery);
    }

    
Checks if a CurrencyConversion is available for the given parameters. 
Params:
conversionQuery – the ConversionQuery, not null.
Returns:
true, if a conversion is accessible from getConversion(ConversionQuery)./**
     * Checks if a {@link javax.money.convert.CurrencyConversion} is available for the given parameters.
     *
     * @param conversionQuery the {@link javax.money.convert.ConversionQuery}, not null.
     * @return true, if a conversion is accessible from {@link #getConversion(ConversionQuery)}.
     */
    public static boolean isConversionAvailable(ConversionQuery conversionQuery){
        return getMonetaryConversionsSpi().isConversionAvailable(conversionQuery);
    }

    
Checks if a CurrencyConversion is available for the given parameters. 
Params:
currencyCode – The currencoy code, resolvable by Monetary.getCurrency(String, String...)
providers –    Additional providers, for building a provider chain
Returns:
true, if a conversion is accessible from getConversion(String, String...)./**
     * Checks if a {@link javax.money.convert.CurrencyConversion} is available for the given parameters.
     *
     * @param currencyCode The currencoy code, resolvable by {@link javax.money.Monetary#getCurrency
     *                     (String, String...)}
     * @param providers    Additional providers, for building a provider chain
     * @return true, if a conversion is accessible from {@link #getConversion(String, String...)}.
     */
    public static boolean isConversionAvailable(String currencyCode, String... providers){
        return getMonetaryConversionsSpi()
                .isConversionAvailable(Monetary.getCurrency(currencyCode), providers);
    }

    
Checks if a CurrencyConversion is available for the given parameters. 
Params:
termCurrency – the terminating or target currency, not null
providers –    Additional providers, for building a provider chain
Returns:
true, if a conversion is accessible from getConversion(String, String...)./**
     * Checks if a {@link javax.money.convert.CurrencyConversion} is available for the given parameters.
     *
     * @param termCurrency the terminating or target currency, not {@code null}
     * @param providers    Additional providers, for building a provider chain
     * @return true, if a conversion is accessible from {@link #getConversion(String, String...)}.
     */
    public static boolean isConversionAvailable(CurrencyUnit termCurrency, String... providers){
        return getMonetaryConversionsSpi()
                .isConversionAvailable(termCurrency, providers);
    }

    
Access an instance of CurrencyConversion using the given providers as a provider chain. Use getConversionProviderNames()s to check, which are available. 
Throws:
IllegalArgumentException – if no such ExchangeRateProvider is available.
Returns:
the exchange rate provider./**
     * Access an instance of {@link CurrencyConversion} using the given
     * providers as a provider chain. Use {@link #getConversionProviderNames()}s
     * to check, which are available.
     *
     * @return the exchange rate provider.
     * @throws IllegalArgumentException if no such {@link ExchangeRateProvider} is available.
     */
    public static ExchangeRateProvider getExchangeRateProvider(String... providers){
        if(providers.length == 0){
            List<String> defaultProviderChain = getDefaultConversionProviderChain();
            return getMonetaryConversionsSpi().getExchangeRateProvider(ConversionQueryBuilder.of().setProviderNames(
                    defaultProviderChain.toArray(new String[defaultProviderChain.size()])).build());
        }
        ExchangeRateProvider provider = getMonetaryConversionsSpi()
                .getExchangeRateProvider(ConversionQueryBuilder.of().setProviderNames(providers).build());
        return Optional.ofNullable(provider)
                .orElseThrow(() -> new MonetaryException("No such rate provider: " + Arrays.toString(providers)));
    }

	
Access an instance of CurrencyConversion using the ExchangeRateProviderSupplier. 
Params:
provider – 
           the exchange rate provider.
providers – 
           the exchange rate provider.
Throws:
IllegalArgumentException –  if no such ExchangeRateProvider is available.
Returns:
the exchange rate provider./**
	 * Access an instance of {@link CurrencyConversion} using the
	 * {@link ExchangeRateProviderSupplier}.
	 *
	 * @param provider
	 *            the exchange rate provider.
	 * @param providers
	 *            the exchange rate provider.
	 * @return the exchange rate provider.
	 * @throws IllegalArgumentException
	 *             if no such {@link ExchangeRateProvider} is available.
	 */
	public static ExchangeRateProvider getExchangeRateProvider(
			ExchangeRateProviderSupplier provider,
			ExchangeRateProviderSupplier... providers) {

		List<ExchangeRateProviderSupplier> suppliers = new ArrayList<>();
		suppliers.add(Objects.requireNonNull(provider));
        suppliers.addAll(Arrays.asList(providers));

		String[] array = suppliers.stream()
				.map(ExchangeRateProviderSupplier::get).toArray(String[]::new);
		return getExchangeRateProvider(array);

	}
    
Access an instance of CurrencyConversion using the given providers as a provider chain. Use getConversionProviderNames() to check, which are available. 
Throws:
IllegalArgumentException – if no such ExchangeRateProvider is available.
Returns:
the exchange rate provider./**
     * Access an instance of {@link CurrencyConversion} using the given
     * providers as a provider chain. Use {@link #getConversionProviderNames()}
     * to check, which are available.
     *
     * @return the exchange rate provider.
     * @throws IllegalArgumentException if no such {@link ExchangeRateProvider} is available.
     */
    public static ExchangeRateProvider getExchangeRateProvider(ConversionQuery conversionQuery){
        return getMonetaryConversionsSpi()
                .getExchangeRateProvider(conversionQuery);
    }

    
Checks if a ExchangeRateProvider is available for the given parameters. 
Params:
conversionQuery – the ConversionQuery, not null.
Returns:
true, if a rate provider is accessible from getExchangeRateProvider(ConversionQuery)}./**
     * Checks if a {@link javax.money.convert.ExchangeRateProvider} is available for the given parameters.
     *
     * @param conversionQuery the {@link javax.money.convert.ConversionQuery}, not null.
     * @return true, if a rate provider is accessible from {@link #getExchangeRateProvider(ConversionQuery)}}.
     */
    public static boolean isExchangeRateProviderAvailable(ConversionQuery conversionQuery){
        return getMonetaryConversionsSpi()
                .isExchangeRateProviderAvailable(conversionQuery);
    }


    
Return the (non localized) names of all providers available in the current context. Each id can be used to obtain ExchangeRateProvider or CurrencyConversion instances. 
Returns:
all supported provider ids, never null./**
     * Return the (non localized) names of all providers available in the
     * current context. Each id can be used to obtain
     * {@link ExchangeRateProvider} or {@link CurrencyConversion} instances.
     *
     * @return all supported provider ids, never {@code null}.
     */
    public static Collection<String> getConversionProviderNames(){
        Collection<String> providers = getMonetaryConversionsSpi().getProviderNames();
        if(Objects.isNull(providers)){
            Logger.getLogger(MonetaryConversions.class.getName()).warning(
                    "No supported rate/conversion providers returned by SPI: " +
                            getMonetaryConversionsSpi().getClass().getName());
            return Collections.emptySet();
        }
        return providers;
    }

    
Get the default provider used.
Returns:
the default provider, never null./**
     * Get the default provider used.
     *
     * @return the default provider, never {@code null}.
     */
    public static List<String> getDefaultConversionProviderChain(){
        List<String> defaultChain = getMonetaryConversionsSpi()
                .getDefaultProviderChain();
        Objects.requireNonNull(defaultChain, "No default provider chain provided by SPI: " +
                getMonetaryConversionsSpi().getClass().getName());
        return defaultChain;
    }

}