// Tim Hutcheson
// COP 4331 Mon. & Wed. 3:30
// Stud. ID. 999-99-9999
// Homework #4

// MindReader.java
// ---------------

import java.util.*;

// the MindReader class encapsulates a simple data base (hashTable), a time series
// prediction method and shift buffer, and a table update method for associating the 
// plays of the game and their values in the hashtable.
public class MindReader {
  
  private ShiftBuffer sb;
  private Hashtable ht = new Hashtable ();
  
  // The following variables are used to store the information of the game
  // for use by either a command line version or an applet version of the game.
  
  private String guess;
  private char prediction;
  private int playerScore, Score;
  public boolean Won;

  public MindReader( int size ) {
    sb = new ShiftBuffer( size );
    }
  
  public void reset() { playerScore = 0; Score = 0; sb.reset(); }
  public int Score() { return Score; }
  public int playerScore() { return playerScore; }
  public String getBuffer() { return sb.toString(); }
  
  public String toString() {
    int matchScore = Math.abs(Score - playerScore);
    String str = (Score-playerScore>0)?" down ":" up ";
    return( matchScore + str + "with " + (25 - (Score + playerScore)) + " to go" );
    }

  // play() handles the actual play of the game and can be used by either
  // a command line implementation or an applet implementation.  Interface 
  // and implementation are separated about the variables guess and
  // predicition.
  
  public char play( String guess ) {
    prediction = getPrediction();
    storePlayerGuess( guess.charAt(0) );
    Won = (guess.charAt(0) == prediction);
    if( Won  )
      Score++;
    else 
      playerScore++;
    return prediction;
    }
  
  // getPrediction will return the computers best guess at the expected
  // value of the players move using time sereis prediction methods.
  
  public char getPrediction() {
    HTcounter query = new HTcounter();
    query = (HTcounter)ht.get(sb.toString());
  
    // If the current shifBuffer exists in the database, use its
    // HTcounter object to decide what the best guess is.  If the 
    // key is not present, just use a random guess.
    if( query != null ) {
      int heads = query.getHead();
      int tails = query.getTail();
      if( heads != tails )
        return heads > tails ? 'h' : 't';
      }
    return Math.random() > .5 ? 'h' : 't';
    }
  
  // storePlayerGuess updates the data base at each round of play.
  
  public void storePlayerGuess( char guess ) {
    String key = sb.toString();
    HTcounter counter;
    
    // If the key exists in the hashtable, get handle to its counter.
    // Otherwise create a counter object and insert it in table.  Then
    // use the handle to update the counter values.  Finally shift the 
    // shiftbuffer to insert the guess for the next round.
    if( ht.containsKey(key) ) 
      counter = (HTcounter)ht.get( key );
    else {
      counter = new HTcounter();
      ht.put( key, counter );
      }
    if( guess == 'h' ) counter.incrHead();
    if( guess == 't' ) counter.incrTail();
    sb.shift( guess );
    }

  }