org.hawkular.inventory.paths.DataRole Maven / Gradle / Ivy

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/*
 * Copyright 2014-2016 Red Hat, Inc. and/or its affiliates
 * and other contributors as indicated by the @author tags.
 *
 * Licensed 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.hawkular.inventory.paths;

import java.util.Collection;
import java.util.HashMap;

/**
 * An interface a data entity role must implement.
 *
 * Data entity roles are supposed to be enums, but to ensure type safety, we have to have different enums for
 * different entity types. I.e. resources can only have data of roles from the
 * {@link Resource} enum, resource types only from {@link ResourceType} enum and operation types from the
 * {@link OperationType} enum.
 */
public interface DataRole {

    /**
     * Converts the string representation of the data role to an instance of it. This works across all implementations
     * of DataRole - {@link Resource}, {@link ResourceType} and {@link OperationType}.
     *
     * @param name the name of the data role (one of the values in the above enums)
     * @return the enum instance with given name
     */
    static DataRole valueOf(String name) {
        return Resource.ImplDetail.instances.get(name);
    }

    /**
     * @return an array of all data roles across all enums implementing the interface -
     * {@link Resource}, {@link ResourceType}, {@link OperationType}.
     */
    static DataRole[] values() {
        Collection values = Resource.ImplDetail.instances.values();
        return values.toArray(new DataRole[values.size()]);
    }

    /**
     * @return the unique name of the role
     */
    String name();

    /**
     * @return true if this role represents a schema, false otherwise
     */
    boolean isSchema();

    enum Resource implements DataRole {
        configuration, connectionConfiguration;

        @Override
        public boolean isSchema() {
            return false;
        }


        /**
         * This is an implementation detail of the {@link DataRole} interface and its implementing enums. It has no data
         * accessible to the users.
         *
         * 
Placing this class in this enum has no other purpose but to hide it from the sight of the users -
         * DataRole interface cannot have private members, so we need to put it in some class.
         *
         * Keep this in sync with all the enums that implement the DataRole interface.
         */
        private static final class ImplDetail {
            private static final HashMap instances;

            static {
                instances = new HashMap<>();
                for (Resource r : Resource.values()) {
                    instances.put(r.name(), r);
                }

                for (ResourceType r : ResourceType.values()) {
                    instances.put(r.name(), r);
                }

                for (OperationType r : OperationType.values()) {
                    instances.put(r.name(), r);
                }
            }

            private ImplDetail() {

            }
        }
    }

    enum ResourceType implements DataRole {
        configurationSchema, connectionConfigurationSchema;

        @Override
        public boolean isSchema() {
            return true;
        }
    }

    enum OperationType implements DataRole {
        returnType, parameterTypes;

        @Override
        public boolean isSchema() {
            return true;
        }
    }
}