DMDirc-Client/src/main/java/com/dmdirc/plugins/LegacyServiceLocator.java

/*
 * Copyright (c) 2006-2017 DMDirc Developers
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
 * documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
 * OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package com.dmdirc.plugins;

import java.lang.reflect.Method;
import java.util.Collection;
import java.util.HashSet;

import javax.annotation.Nullable;
import javax.inject.Inject;
import javax.inject.Singleton;

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

import static com.dmdirc.util.LogUtils.USER_ERROR;
import static com.google.common.base.Preconditions.checkNotNull;

/**
 * A service locator backed by a {@link PluginManager} and exported methods.
 */
@Singleton
public class LegacyServiceLocator implements ServiceLocator {

    private static final Logger LOG = LoggerFactory.getLogger(LegacyServiceLocator.class);
    /** The plugin manager to use to find services. */
    private final PluginManager pluginManager;

    @Inject
    public LegacyServiceLocator(final PluginManager pluginManager) {
        this.pluginManager = checkNotNull(pluginManager);
    }

    @Override
    public <T> Collection<T> getAllServices(final Class<T> serviceType) {
        return getServices(serviceType, null);
    }

    @Override
    public <T> T getService(final Class<T> serviceType, final String implementation) {
        final Collection<T> services = getServices(serviceType, implementation);
        return services.isEmpty() ? null : services.iterator().next();
    }

    @SuppressWarnings("unchecked")
    private <T> Collection<T> getServices(final Class<T> serviceType,
            @Nullable final String implementation) {
        checkNotNull(serviceType);
        final Collection<T> services = new HashSet<>();
        pluginManager.getPluginInfos().stream().filter(PluginInfo::isLoaded)
                .forEach(pluginInfo -> {
                    final Plugin plugin = pluginInfo.getPlugin();
                    for (Method method : plugin.getClass().getMethods()) {
                        if (method.isAnnotationPresent(Exported.class) &&
                                method.getParameterTypes().length == 0 &&
                                serviceType.isAssignableFrom(method.getReturnType())) {
                            try {
                                method.setAccessible(true);
                                final Object object = method.invoke(plugin);
                                if (object != null && (implementation == null ||
                                        implementation.equals(object.getClass().getName()))) {
                                    services.add((T) object);
                                }
                            } catch (ReflectiveOperationException ex) {
                                LOG.info(USER_ERROR,
                                        "Unable to execute exported method {} in plugin {}",
                                        method.getName(), pluginInfo.getMetaData().getName(), ex);
                            }
                        }
                    }
                });

        return services;
    }

}