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 com.cloud.host;
  
  import java.util.List;
  import java.util.Set;
  
  import com.cloud.utils.fsm.NoTransitionException;
  import com.cloud.utils.fsm.StateMachine2;
  
  public enum Status {
      Creating(true, false, false),
      Connecting(true, false, false),
      Up(true, false, false),
      Down(true, true, true),
      Disconnected(true, true, true),
      Alert(true, true, true),
      Removed(true, false, true),
      Error(true, false, true),
      Rebalancing(true, false, true),
      Unknown(false, false, false); // null
  
      private final boolean updateManagementServer;
      private final boolean checkManagementServer;
      private final boolean lostConnection;
  
      private Status(boolean updateConnection, boolean checkManagementServer, boolean lostConnection) {
          this.updateManagementServer = updateConnection;
          this.checkManagementServer = checkManagementServer;
          this.lostConnection = lostConnection;
      }
  
      public boolean updateManagementServer() {
          return updateManagementServer;
      }
  
      public boolean checkManagementServer() {
          return checkManagementServer;
      }
  
      public boolean lostConnection() {
          return lostConnection;
      }
  
      public enum Event {
          AgentConnected(false, "Agent connected"),
          PingTimeout(false, "Agent is behind on ping"),
          ShutdownRequested(false, "Shutdown requested by the agent"),
          AgentDisconnected(false, "Agent disconnected"),
          HostDown(false, "Host is found to be down by the investigator"),
          Ping(false, "Ping is received from the host"),
          ManagementServerDown(false, "Management Server that the agent is connected is going down"),
          WaitedTooLong(false, "Waited too long from the agent to reconnect on its own.  Time to do HA"),
          Remove(true, "Host is removed"),
          Ready(false, "Host is ready for commands"),
          RequestAgentRebalance(false, "Request rebalance for the certain host"),
          StartAgentRebalance(false, "Start rebalance for the certain host"),
          RebalanceCompleted(false, "Host is rebalanced successfully"),
          RebalanceFailed(false, "Failed to rebalance the host"),
          Error(false, "An internal error happened");
  
          private final boolean isUserRequest;
          private final String comment;
  
          private Event(boolean isUserRequest, String comment) {
              this.isUserRequest = isUserRequest;
              this.comment = comment;
          }
  
          public String getDescription() {
              return comment;
          }
  
          public boolean isUserRequest() {
              return isUserRequest;
          }
      }
  
      public static StateMachine2<Status, Event, Host> getStateMachine() {
          return s_fsm;
      }
  
      public Status getNextStatus(Event e) throws NoTransitionException {
          return s_fsm.getNextState(this, e);
      }
  
      public Status[] getFromStates(Event e) {
          List<Status> from = s_fsm.getFromStates(this, e);
          return from.toArray(new Status[from.size()]);
      }
  
      public Set<Event> getPossibleEvents() {
          return s_fsm.getPossibleEvents(this);
      }
  
      public static String[] toStrings(Status... states) {
          String[] strs = new String[states.length];
          for (int i = 0; i < states.length; i++) {
              strs[i] = states[i].toString();
          }
          return strs;
      }
  
      protected static final StateMachine2<Status, Event, Host> s_fsm = new StateMachine2<Status, Event, Host>();
      static {
          s_fsm.addTransition(null, Event.AgentConnected, Status.Connecting);
          s_fsm.addTransition(Status.Creating, Event.AgentConnected, Status.Connecting);
          s_fsm.addTransition(Status.Creating, Event.Error, Status.Error);
          s_fsm.addTransition(Status.Connecting, Event.AgentConnected, Status.Connecting);
          s_fsm.addTransition(Status.Connecting, Event.Ready, Status.Up);
          s_fsm.addTransition(Status.Connecting, Event.PingTimeout, Status.Alert);
          s_fsm.addTransition(Status.Connecting, Event.ShutdownRequested, Status.Disconnected);
          s_fsm.addTransition(Status.Connecting, Event.HostDown, Status.Down);
          s_fsm.addTransition(Status.Connecting, Event.Ping, Status.Connecting);
          s_fsm.addTransition(Status.Connecting, Event.ManagementServerDown, Status.Disconnected);
          s_fsm.addTransition(Status.Connecting, Event.StartAgentRebalance, Status.Rebalancing);
          s_fsm.addTransition(Status.Connecting, Event.AgentDisconnected, Status.Alert);
          s_fsm.addTransition(Status.Up, Event.PingTimeout, Status.Alert);
          s_fsm.addTransition(Status.Up, Event.AgentDisconnected, Status.Alert);
          s_fsm.addTransition(Status.Up, Event.ShutdownRequested, Status.Disconnected);
          s_fsm.addTransition(Status.Disconnected, Event.ShutdownRequested, Status.Disconnected);
          s_fsm.addTransition(Status.Down, Event.ShutdownRequested, Status.Disconnected);
          s_fsm.addTransition(Status.Rebalancing, Event.ShutdownRequested, Status.Disconnected);
          s_fsm.addTransition(Status.Up, Event.HostDown, Status.Down);
          s_fsm.addTransition(Status.Up, Event.Ping, Status.Up);
          s_fsm.addTransition(Status.Up, Event.AgentConnected, Status.Connecting);
          s_fsm.addTransition(Status.Up, Event.ManagementServerDown, Status.Disconnected);
          s_fsm.addTransition(Status.Up, Event.StartAgentRebalance, Status.Rebalancing);
          s_fsm.addTransition(Status.Up, Event.Remove, Status.Removed);
          s_fsm.addTransition(Status.Disconnected, Event.PingTimeout, Status.Alert);
          s_fsm.addTransition(Status.Disconnected, Event.AgentConnected, Status.Connecting);
          s_fsm.addTransition(Status.Disconnected, Event.Ping, Status.Up);
          s_fsm.addTransition(Status.Disconnected, Event.HostDown, Status.Down);
          s_fsm.addTransition(Status.Disconnected, Event.ManagementServerDown, Status.Disconnected);
          s_fsm.addTransition(Status.Disconnected, Event.WaitedTooLong, Status.Alert);
          s_fsm.addTransition(Status.Disconnected, Event.Remove, Status.Removed);
          s_fsm.addTransition(Status.Disconnected, Event.AgentDisconnected, Status.Disconnected);
          s_fsm.addTransition(Status.Down, Event.AgentConnected, Status.Connecting);
          s_fsm.addTransition(Status.Down, Event.Remove, Status.Removed);
          s_fsm.addTransition(Status.Down, Event.ManagementServerDown, Status.Down);
          s_fsm.addTransition(Status.Down, Event.AgentDisconnected, Status.Down);
          s_fsm.addTransition(Status.Down, Event.PingTimeout, Status.Down);
          s_fsm.addTransition(Status.Down, Event.HostDown, Status.Down);
          s_fsm.addTransition(Status.Alert, Event.AgentConnected, Status.Connecting);
          s_fsm.addTransition(Status.Alert, Event.Ping, Status.Up);
          s_fsm.addTransition(Status.Alert, Event.Remove, Status.Removed);
          s_fsm.addTransition(Status.Alert, Event.ManagementServerDown, Status.Alert);
          s_fsm.addTransition(Status.Alert, Event.AgentDisconnected, Status.Alert);
          s_fsm.addTransition(Status.Alert, Event.ShutdownRequested, Status.Disconnected);
          s_fsm.addTransition(Status.Alert, Event.HostDown, Status.Down);
          s_fsm.addTransition(Status.Rebalancing, Event.RebalanceFailed, Status.Disconnected);
          s_fsm.addTransition(Status.Rebalancing, Event.RebalanceCompleted, Status.Connecting);
          s_fsm.addTransition(Status.Rebalancing, Event.ManagementServerDown, Status.Disconnected);
          s_fsm.addTransition(Status.Rebalancing, Event.AgentConnected, Status.Connecting);
          s_fsm.addTransition(Status.Rebalancing, Event.AgentDisconnected, Status.Rebalancing);
          s_fsm.addTransition(Status.Error, Event.AgentConnected, Status.Connecting);
      }
  
      public static void main(String[] args) {
          System.out.println("Finite State Machine for Host:");
          System.out.println(s_fsm.toString());
      }
  }
  