// Counter.java
// Solution to CS 5 Short Assignment #6 by THC.

// Implementation of the class Counter.

// Define a class of Counter objects. A counter holds a single integer
// in the range 0..(myLimit - 1). Each time tick() is called the
// counter increases, wrapping back to 0 when it reaches myLimit.

// This version allows us to specify how many digits a Counter displays.
// It overloads the constructor, so that we can create different kinds
// of Counters. It also provides a method to return the value in the
// Counter and a method to reset the Counter to a particular value.

// This version is more efficient because it doesn't create a
// DecimalFormat object upon each call of show, instead creating a
// DecimalFormat object in the constructors.  It also adds a toString
// method and a constructor that makes a copy of a Counter.

import java.text.DecimalFormat;

public class Counter {
  private int myLimit; // Upper limit on the counter
  private int myValue; // Current value
  private DecimalFormat myFormatter; // Formatter for displaying

  // Constructors for the Counter class.

  // Create a Counter with myLimit 10, myValue 0, and 1 digit to display.
  public Counter() {
    myLimit = 10;
    myValue = 0;
    myFormatter = createFormat(digitsToDisplay());
  }

  // Create a Counter with myLimit set to limit, myValue set to 0, and
  // exactly as many digits as we'll need to display the largest value
  // that will be displayed.
  public Counter(int limit) {
    myLimit = limit;
    myValue = 0;
    myFormatter = createFormat(digitsToDisplay());
  }

  // Create a Counter with myLimit set to limit, myValue set to 0, and
  // the number of digits given as a parameter, but always at least as
  // many as necessary for the largest value displayed.
  public Counter(int limit, int digits) {
    myLimit = limit;
    myValue = 0;

    // Determine the least number of digits we can use for the display.
    int minDisplaySize = digitsToDisplay();

    // Complain if too few digits were requested.
    if (minDisplaySize > digits)
      System.out.println("You asked to display " + digits
          + (digits > 1 ? " digits, " : " digit, ")
          + "but you need at least " + minDisplaySize + ".");

    // Use the better value.
    myFormatter = createFormat(Math.max(minDisplaySize, digits));
  }
  
  // Create a Counter that is a copy of another Counter.
  public Counter(Counter other) {
    myLimit = other.myLimit;
    myValue = other.myValue;
    myFormatter = other.myFormatter;
  }

  // Display the value of a Counter, padding with as many leading zeros
  // as necessary.
  public void show() {
    System.out.print(toString());
  }
  
  // Return a String that gives the value of a Counter, padding with as
  // many leading zeros as necessary.
  public String toString() {
    return myFormatter.format(myValue);
  }

  // Increment the value of a Counter, wrapping around if it
  // hits the limit.
  public void tick() {
    myValue++;
    if (myValue == myLimit) // Has it hit the limit?
      myValue = 0; // Wrap if it has
  }
  
  // Return the value of a Counter.
  public int getValue() {
    return myValue;
  }

  // Reset a Counter to a given value, as long as it's legal.
  public void reset(int value) {
    if (0 <= value && value < myLimit)
      myValue = value;
  }

  // Here's a helper method. It is called only by methods in this class,
  // so it is private. It returns how many digits are needed to display
  // the largest value that the Counter may have, assuming that myLimit
  // has already been set.
  // That number, by the way, is the number of digits in limit-1.
  private int digitsToDisplay() {
    return (Integer.toString(myLimit - 1)).length();
  }
  
  // Another helper method, which creates a DecimalFormat object for
  // formatting the value.
  private DecimalFormat createFormat(int digits) {
    // Create a String that is all 0's, and the length is a given number
    // of digits.
    String zeros = "";
    for (int digit = 1; digit <= digits; digit++)
      zeros += "0";

    // Now use that to create a DecimalFormat object.
    return new DecimalFormat(zeros);
  }
}