/*
 * LoadBalanceManager.java
 *
 * Load Balance Manager data and operations for random selection of 
 * a subset of the set of servers.
 *
 *  Created by: Arthur L. Blais
 *              Visteon/Ford Microelectronics Inc.
 *              Colorado Springs, CO
 *
 *  Date: Fri Sep 24 08:43:13 MDT 1999
 *
 *  Wed Mar 29 07:21:05 MST 2000: add random selection for adversarial tests
 *
 ****************************************************************************
 *
 *   Class Methods
 *
 *
 ****************************************************************************
 */
 
import java.util.Random;

public class LoadBalanceManager {

  int id;                                // id number
  int serverCount;                       // total number of servers
  int server[];                          // server reqeust count
  int managerType;                       // LBM type 0 = subset, 1 = random

  // Pseudo-Random Variate Seeds
  private static long seed = 98391;
  // random number instances
  private static Random randNumber; // = new Random( seed );

  public LoadBalanceManager( int n, int s, int t ) {

    id = n;
    serverCount = s;
    managerType = t;
    server = new int[ serverCount ];

    for ( int i = 0; i < serverCount; i++ ) {
       server[i] = 0;
    }

    randNumber  = new Random( seed );
  }

  /**
   * getId
   */
  int getId() {
    return id;
  }  

  /**
   * requestComplete
   */
  void requestComplete( int s ) {

     server[s]--;
  }

  /**
   * nextServer
   *
   * Greedy selection of the server with the lowest load from a 
   * random subset of the set of servers
   *
   */
  int nextServer() {

    if ( serverCount == 1 ) {
      server[0]++;
      return 0;
    }

    int nextServer;

    if ( managerType == 1 ) {
      // random manager
      nextServer = Math.abs( randNumber.nextInt() ) % serverCount;
      server[nextServer]++;

      return( nextServer );  
    }
      
    int s0 = Math.abs( randNumber.nextInt() ) % serverCount;
    int s1 = Math.abs( randNumber.nextInt() ) % serverCount;

    while ( s0 == s1 ) {
      s1 = Math.abs( randNumber.nextInt() ) % serverCount;
    }

    if ( server[ s0 ] <= server[ s1 ] ) {
      nextServer = s0;
    }
    else {
      nextServer = s1;
    }

    server[nextServer]++;

    return( nextServer );  
  }

}