utils/src/main/java/org/jclouds/karaf/utils/ServiceHelper.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.jclouds.karaf.utils;

import com.google.common.base.Strings;
import org.jclouds.Context;
import org.jclouds.View;
import org.jclouds.compute.ComputeService;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.LinkedList;
import java.util.List;

public class ServiceHelper {

    private ServiceHelper() {
        //Utility Class
    }

    /**
     * Returns the cache keys for a given Service.
     *
     * @param service
     * @return
     */
    public static <T> List<String> findCacheKeysForService(T service) {
        List<String> keys = new LinkedList<String>();
        String contextName = toName(service);
        String providerOrApi = toId(service);
        if (contextName != null) {
            keys.add(contextName);
        }
        if (providerOrApi != null) {
            keys.add(providerOrApi);
        }
        return keys;
    }

    /**
     * Chooses a {@link ComputeService} that matches the specified a service id or a provider / api.
     *
     * @param id
     * @param providerOrApi
     * @param services
     * @return
     */
    public static <T> T getService(String id, String providerOrApi, List<T> services) {
        if (!Strings.isNullOrEmpty(id)) {
            T service = null;
            for (T svc : services) {
                if (id.equals(toName(svc))) {
                    service = svc;
                    break;
                }
            }
            if (service == null) {
                throw new IllegalArgumentException("No service with id" + id + " found.");
            }
            return service;
        }

        if (!Strings.isNullOrEmpty(providerOrApi)) {
            T service = null;
            for (T svc : services) {
                if (providerOrApi.equals(toId(svc))) {
                    service = svc;
                    break;
                }
            }
            if (service == null) {
                throw new IllegalArgumentException("No Provider or Api named " + providerOrApi + " found.");
            }
            return service;
        } else {
            if (services.size() == 0) {
                throw new IllegalArgumentException("No providers are present.  Note: It takes a couple of seconds for the provider to initialize.");
            } else if (services.size() != 1) {
                StringBuilder sb = new StringBuilder();
                for (T svc : services) {
                    if (sb.length() > 0) {
                        sb.append(", ");
                    }
                    sb.append(toId(svc));
                }
                throw new IllegalArgumentException("Multiple providers/apis are present, please select one using the --provider/--api argument in the following values: " + sb.toString());
            } else {
                return services.get(0);
            }
        }
    }

    /**
     * Extracts the Id of the Service.
     *
     * @param service
     * @param <T>
     * @return
     */
    public static <T> String toId(T service) {
        String id = null;
        try {
            Context context = toContext(service);
            if (View.class.isAssignableFrom(context.getClass())) {
                id = ((View) context).unwrap().getId();
            } else {
                id = context.getId();
            }
        } catch (IllegalArgumentException ex) {
            //Fallback to pure reflection
            id = callMethod(service, "getId", String.class);
        }
        return id;
    }

    /**
     * Extracts the Name of the Service.
     *
     * @param service
     * @param <T>
     * @return
     */
    public static <T> String toName(T service) {
        String name = null;
        try {
            Context context = toContext(service);
            if (View.class.isAssignableFrom(context.getClass())) {
                name = ((View) context).unwrap().getName();
            } else {
                name = context.getName();
            }
        } catch (IllegalArgumentException ex) {
            //Fallback to pure reflection
            name = callMethod(service, "getName", String.class);
        }
        return name;
    }

    /**
     * Extracts the {@link Context}.
     *
     * @param service
     * @param <T>
     * @return
     */
    public static <T> Context toContext(T service) {
        Context ctx = null;
        Class c = service.getClass();
        try {
            //Ugly way to get the Context, but there doesn't seem to be a better one.
            Method m = c.getMethod("getContext");
            Object obj = m.invoke(service);
            if (Context.class.isAssignableFrom(obj.getClass())) {
                ctx = (Context) obj;
            } else if (View.class.isAssignableFrom(obj.getClass())) {
                ctx = ((View) obj).unwrap();
            } else {
                throw new IllegalArgumentException("Service doesn't have a context.");
            }
        } catch (NoSuchMethodException e) {
            throw new IllegalArgumentException(e);
        } catch (InvocationTargetException e) {
            throw new IllegalArgumentException(e);
        } catch (IllegalAccessException e) {
            throw new IllegalArgumentException(e);
        }
        return ctx;
    }

    /**
     * Extracts the {@link Context}.
     *
     * @param service
     * @param <T>
     * @return
     */
    public static <S, T> T callMethod(S service, String methodName, Class<T> returnType) {
        T result = null;
        Class c = service.getClass();
        try {
            //Ugly way to get the Context, but there doesn't seem to be a better one.
            Method m = c.getMethod(methodName);
            Object obj = m.invoke(service);
            if (returnType.isAssignableFrom(obj.getClass())) {
                result = returnType.cast(obj);
            } else {
                throw new IllegalArgumentException("Service doesn't have a context.");
            }
        } catch (NoSuchMethodException e) {
            throw new IllegalArgumentException(e);
        } catch (InvocationTargetException e) {
            throw new IllegalArgumentException(e);
        } catch (IllegalAccessException e) {
            throw new IllegalArgumentException(e);
        }
        return result;
    }
}