/* 
 * Racquetball/Volleyball Simulation:  
 *    Solution Alternative 2:  Store game, simulation data in static variables
 *    Serve-by-Serve Recursive Approach
 *    Type of game given in a command-line parameter
 * Copyright(c) 2011 by Henry M. Walker
 *
 * This code is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * @author Henry M. Walker
 */

// The Math library is needed for its random() function
import java.lang.Math;

/**
 * This class simulates a volleyball or racquetball game
 * between players/teams A and B, based on the probability
 * that A will win a volley.  1000 games are simulated,
 * with the probability of A winning a volley being 
 * 0.40, 0.41, ..., 0.59, 0.60 .
 */
public class Game4Recur {
    // Edit these lines to indicate the game to be simulated
    // and the number of games to simulate for each server probability
    public static String game;       // "racquetball" or "volleyball"
    public static int numberOfGames = 1000;
    public static boolean winByTwo;  // winner must be ahead by at least 2 points

    // use the following field to enable tracing of results of each game
    public static boolean printGame = false;

    /**
     * Format a probability (a number between 0.0 and 1.0)
     * as a 2-character integer percentage, followed by a
     * "%" character.
     */
    public static String formatPercent (double value)
    {
	String str = "" + Math.round(value * 100.0);
	while (str.length() < 3)
	    str = " " + str;
	return str + "%";
    }
	
    /**
     * Play one game of racquetball or volleyball to conclusion
     * @parms  server and receiver indicate the team "A" or "B"
     *         probWinVolley specifies the likelihood the server wins a volley
     *         serverScore, recScore contain current score of
     *             server and receiver
     * @returns winner of game: either "A" or "B"
     */
    public static String playUntilWin (String server, String receiver,
				       double probWinVolley, 
				       int serverScore, int recScore) 
     {  // serve
	if (Math.random() < probWinVolley)
	    { // score point
		serverScore++;
	      // if win, return winner
		if ((serverScore >= 15)
		    && ((! winByTwo)
			 || (serverScore >= recScore + 2)))
		    { if (printGame)
			    System.out.println (server + " - Scores:  " 
						+ serverScore 
						+ " / " + recScore);
		      return server;
		    }
	      // if not win, serve again
		{return playUntilWin (server, receiver, probWinVolley, 
				      serverScore, recScore);
		}

	    }
	else
	    { // other side wins; other player serves 
		return playUntilWin (receiver, server, 1.0-probWinVolley,
				     recScore, serverScore);
	    }
    }

    /**
     * Run simulation of 1000 games for probability of "A" winning
     *   a volley covering the range 0.40, 0.41, ..., 0.59, 0.60.
     * For each probability of "A" winning,
     *   simulate games with Player/Team A always serving first
     *   print one line with the percentage of volleys won by A and B 
     *     and percentage of games won by A and B
     */
    public static void main (String [] args)
    {   game = "";    // initially, game is unspecified

        // check any command-line argument
	if (args.length >= 1)
	    {
		game = args[0];
	    }

	// determine if server must win by 2 (e.g., in volleyball)
        winByTwo = game.equals("volleyball");

	// print headings
	System.out.println ("\nSimulation of " + game
			    + " based on " + numberOfGames + " games");
	System.out.println ("Must win by 2:  " + winByTwo);
	System.out.println ();
	System.out.println ("    Probabilities         Percentage");
	System.out.println (" for winning volley        of Wins");
	System.out.println ("     A       B            A        B");
        System.out.println ();
	
	// Simulate games for 40% to 60% probabilities for A
	for (int prob40To60 = 40; prob40To60 <= 60; prob40To60++)
	    {
	      double probWinVolley = prob40To60 / 100.0;
 
	      // Simulate games for a given probability
	      int AWins = 0;  // at first neither A nor B has won any games
	      int BWins = 0;
	      for (int i = 0; i < numberOfGames; i++)
		  { // tally winner of game
		    if (playUntilWin ("A", "B", probWinVolley, 0, 0).equals("A"))
			AWins++;
		    else
			BWins++;
		  }
	      System.out.println ("   "
			  + formatPercent(probWinVolley)   + "    " 
			  + formatPercent(1-probWinVolley) + "         "
			  + formatPercent(((double) AWins) / numberOfGames)
			  + "     "
			  + formatPercent(((double) BWins) / numberOfGames));
	    }
	System.out.println ("\nEnd of Simulation\n");
    }
}