// This file contains excerpts from the textbook Concrete
// Abstractions: An Introduction to Computer Science Using Scheme, by
// Max Hailperin, Barbara Kaiser, and Karl Knight, Copyright (c) 1998
// by the authors. Full text is available for free at
// http://www.gustavus.edu/+max/concrete-abstractions.html

// Warning: this class is missing some necessary synchronized keywords,
// because it is intended as an exercise in debugging concurrent programs.

public class CompoundingThread extends Thread {

  private boolean enabled;
  private double initial, current, multiplier;
  private int year;
  private Compounder c;
  private java.text.NumberFormat fmt;

  // Invariant:
  //   (1) current = initial * (multiplier raised to the
  //       year power)
  //   (2) year also specifies how many lines of output c has
  //       gotten since it was last cleared, corresponding to
  //       years from 0 up through year-1.
           

  public CompoundingThread(Compounder comp){
    c = comp;
    fmt = java.text.NumberFormat.getCurrencyInstance();
  }

  synchronized private void waitUntilEnabled()
       throws InterruptedException {
    while(!enabled){
      wait();
    }
  }

  synchronized public void disable(){
    enabled = false;
  }

  synchronized public void enable(){
    enabled = true;
    notify();
  }

  public void run(){
    try{
      while(true){
        Thread.sleep(1000);
        waitUntilEnabled();
        doYear();
      }
    } catch(InterruptedException e){
      // ignore, but stop running
    }
  }

  private void doYear(){
    c.outputLine("After " + year + " years, " +fmt.format(current));
    year++;
    current *= multiplier;
  }

  public void setInitialAmount(double amount){
    initial = amount;
    initialize();
  }

  public void setInterestRate(double rate){
    // note that a rate of 5% (e.g.) would be .05, *not* 5
    multiplier = 1 + rate;
    initialize();
  }

  private void initialize(){
    current = initial;
    year = 0;
    c.clearOutput();
  }
}