/**
 * 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.facebook.infrastructure.gms;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

import com.facebook.infrastructure.io.ICompactSerializer;

/**
 * This abstraction represents the state associated with a particular node which
 * an application wants to make available to the rest of the nodes in the
 * cluster. Whenever a peice of state needs to be disseminated to the rest of
 * cluster wrap the state in an instance of <i>ApplicationState</i> and add it
 * to the Gossiper.
 * 
 * For eg. if we want to disseminate load information for node A do the
 * following:
 * 
 * ApplicationState loadState = new ApplicationState(<string reprensentation of
 * load>); Gossiper.instance().addApplicationState("LOAD STATE", loadState);
 * 
 * Author : Avinash Lakshman ( alakshman@facebook.com) & Prashant Malik (
 * pmalik@facebook.com )
 */

public class ApplicationState {
  private static ICompactSerializer<ApplicationState> serializer_;
  static {
    serializer_ = new ApplicationStateSerializer();
  }

  int version_;
  String state_;

  ApplicationState(String state, int version) {
    state_ = state;
    version_ = version;
  }

  public static ICompactSerializer<ApplicationState> serializer() {
    return serializer_;
  }

  /**
   * Wraps the specified state into a ApplicationState instance.
   * 
   * @param state
   *          string representation of arbitrary state.
   */
  public ApplicationState(String state) {
    state_ = state;
    version_ = VersionGenerator.getNextVersion();
  }

  public String getState() {
    return state_;
  }

  int getStateVersion() {
    return version_;
  }
}

class ApplicationStateSerializer implements
    ICompactSerializer<ApplicationState> {
  public void serialize(ApplicationState appState, DataOutputStream dos)
      throws IOException {
    dos.writeUTF(appState.state_);
    dos.writeInt(appState.version_);
  }

  public ApplicationState deserialize(DataInputStream dis) throws IOException {
    String state = dis.readUTF();
    int version = dis.readInt();
    return new ApplicationState(state, version);
  }
}
