/*
 * Units of Measurement Reference Implementation
 * Copyright (c) 2005-2018, Jean-Marie Dautelle, Werner Keil, Otavio Santana.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions
 *    and the following disclaimer in the documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of JSR-385, Indriya nor the names of their contributors may be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package tech.units.indriya.spi;

import javax.measure.Quantity;
import javax.measure.spi.QuantityFactory;
import javax.measure.spi.ServiceProvider;
import javax.measure.spi.SystemOfUnitsService;
import javax.measure.spi.UnitFormatService;

import tech.units.indriya.quantity.DefaultQuantityFactory;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.ServiceLoader;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * This class extends the {@link javax.measure.spi.ServiceProvider} class and
 * hereby uses the JDK {@link java.util.ServiceLoader} to load the required
 * services.
 *
 * @author Werner Keil
 * @version 1.0
 * @since 1.0
 */
public class DefaultServiceProvider extends ServiceProvider implements Comparable<ServiceProvider> {
        /**
         * List of services loaded, per class.
         */
        @SuppressWarnings("rawtypes")
        private final Map<Class, List<Object>> servicesLoaded = new ConcurrentHashMap<>();

        private static final Comparator<Object> SERVICE_COMPARATOR = DefaultServiceProvider::compareServices;

        @SuppressWarnings("rawtypes")
        private final Map<Class, QuantityFactory> QUANTITY_FACTORIES = new ConcurrentHashMap<>();

        /**
         * Returns a priority value of 10.
         *
         * @return 10, overriding the default provider.
         */
        @Override
        public int getPriority() {
                return 10;
        }

        /**
         * Loads and registers services.
         *
         * @param serviceType
         *            The service type.
         * @param <T>
         *            the concrete type.
         * @return the items found, never {@code null}.
         */
        protected <T> List<T> getServices(final Class<T> serviceType) {
                @SuppressWarnings("unchecked")
                List<T> found = (List<T>) servicesLoaded.get(serviceType);
                if (found != null) {
                        return found;
                }

                return loadServices(serviceType);
        }

        protected <T> T getService(Class<T> serviceType) {
                List<T> services = getServices(serviceType);
                if (services.isEmpty()) {
                        return null;
                }
                return services.get(0);
        }

        static int compareServices(Object o1, Object o2) {
                int prio1 = 0;
                int prio2 = 0;
                if (prio1 < prio2) {
                        return 1;
                }
                if (prio2 < prio1) {
                        return -1;
                }
                return o2.getClass().getSimpleName().compareTo(o1.getClass().getSimpleName());
        }

        /**
         * Loads and registers services.
         *
         * @param serviceType
         *            The service type.
         * @param <T>
         *            the concrete type.
         * @return the items found, never {@code null}.
         */
        private <T> List<T> loadServices(final Class<T> serviceType) {
                List<T> services = new ArrayList<>();
                try {
                        for (T t : ServiceLoader.load(serviceType)) {
                                services.add(t);
                        }
                        Collections.sort(services, SERVICE_COMPARATOR);
                        @SuppressWarnings("unchecked")
                        final List<T> previousServices = (List<T>) servicesLoaded.putIfAbsent(serviceType, (List<Object>) services);
                        return Collections.unmodifiableList(previousServices != null ? previousServices : services);
                } catch (Exception e) {
                        Logger.getLogger(DefaultServiceProvider.class.getName()).log(Level.WARNING,
                                        "Error loading services of type " + serviceType, e);
                        Collections.sort(services, SERVICE_COMPARATOR);
                        return services;
                }
        }

        @Override
        public int compareTo(ServiceProvider o) {
                return Integer.compare(getPriority(), o.getPriority());
        }

        @Override
        public SystemOfUnitsService getSystemOfUnitsService() {
                return getService(SystemOfUnitsService.class);
        }

        @Override
        public UnitFormatService getUnitFormatService() {
                return getService(UnitFormatService.class);
        }

         /**
           * Return a factory for this quantity
           * 
           * @param quantity
           *          the quantity type
           * @return the {@link QuantityFactory}
           * @throws NullPointerException
           */
          @Override
          @SuppressWarnings("unchecked")
          public final <Q extends Quantity<Q>> QuantityFactory<Q> getQuantityFactory(Class<Q> quantity) {
            if (quantity == null)
              throw new NullPointerException();
            if (!QUANTITY_FACTORIES.containsKey(quantity)) {
              synchronized (QUANTITY_FACTORIES) {
                QUANTITY_FACTORIES.put(quantity, DefaultQuantityFactory.getInstance(quantity));
              }
            }
            return QUANTITY_FACTORIES.get(quantity);
          }
}