content: /*
   * 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.apache.ambari.server.state;
  
  import java.util.List;
  
  /**
   * The {@link RepositoryVersionState} represents the state of a repository on a
   * particular host. Because hosts can contain a mixture of components from
   * different repositories, there can be any combination of
   * {@link RepositoryVersionState#CURRENT}} entries for a single host. A host may
   * not have multiple entries for the same repository.
   * <p/>
   *
   *
   * <pre>
   * Step 1: Initial Configuration
   * Version 1 is CURRENT
   *
   * Step 2: Add another repository and trigger distributing repositories/installing packages
   * Version 1: CURRENT
   * Version 2: INSTALLING
   *
   * Step 3: distributing repositories/installing packages action finishes successfully or fails
   * Version 1: CURRENT
   * Version 2: INSTALLED
   *
   * or
   *
   * Version 1: CURRENT
   * Version 2: INSTALL_FAILED (a retry can set this back to INSTALLING)
   *
   * Step 4: Perform an upgrade of every component on the host from version 1 to version 2
   * Version 1: INSTALLED
   * Version 2: CURRENT
   *
   * Step 4a: Perform an upgrade of a single component, leaving other components on the prior version
   * Version 1: CURRENT
   * Version 2: CURRENT
   *
   * Step 4b: May revert to the original version via a downgrade, which is technically still an upgrade to a version
   * and eventually becomes
   *
   * Version 1: CURRENT
   * Version 2: INSTALLED
   *
   * *********************************************
   * Start states: NOT_REQUIRED, INSTALLING, CURRENT
   * Allowed Transitions:
   * INSTALLED -> CURRENT
   * INSTALLING -> INSTALLED | INSTALL_FAILED | OUT_OF_SYNC
   * INSTALLED -> INSTALLED | INSTALLING | OUT_OF_SYNC
   * OUT_OF_SYNC -> INSTALLING
   * INSTALL_FAILED -> INSTALLING
   * CURRENT -> INSTALLED
   * </pre>
   */
  public enum RepositoryVersionState {
    /**
     * Repository version is not required
     */
    NOT_REQUIRED(0),
  
    /**
     * Repository version that is in the process of being installed.
     */
    INSTALLING(3),
  
    /**
     * Repository version that is installed and supported but not the active version.
     */
    INSTALLED(2),
  
    /**
     * Repository version that during the install process failed to install some components.
     */
    INSTALL_FAILED(5),
  
    /**
     * Repository version that is installed for some components but not for all.
     */
    OUT_OF_SYNC(4),
  
    /**
     * Repository version that is installed and supported and is the active version.
     */
    CURRENT(1);
  
    private final int weight;
  
    /**
     * Constructor.
     *
     * @param weight
     *          the weight of the state.
     */
    private RepositoryVersionState(int weight) {
      this.weight = weight;
    }
  
    /**
     * Gets a single representation of the repository state based on the supplied
     * states.
     *
     * @param states
     *          the states to calculate the aggregate for.
     * @return the "heaviest" state.
     */
    public static RepositoryVersionState getAggregateState(List<RepositoryVersionState> states) {
      if (null == states || states.isEmpty()) {
        return NOT_REQUIRED;
      }
  
      RepositoryVersionState heaviestState = states.get(0);
      for (RepositoryVersionState state : states) {
        if (state.weight > heaviestState.weight) {
          heaviestState = state;
        }
      }
  
      return heaviestState;
    }
  
  }
  