/* 
 * BigInt.java
 *
 * A class for objects that represent non-negative integers of 
 * up to 20 digits.
 */

public class BigInt  {
    // the maximum number of digits in a BigInt -- and thus the length
    // of the digits array
    private static final int SIZE = 20;
    
    // the array of digits for this BigInt object
    private int[] digits;
    
    // the number of significant digits in this BigInt object
    private int numSigDigits;

    /*
     * Default, no-argument constructor -- creates a BigInt that 
     * represents the number 0.
     */
    public BigInt() {
        this.digits = new int[SIZE];
        this.numSigDigits = 1;  // 0 has one sig. digit--the rightmost 0!
    }

    /*
     *
     * YOUR METHODS
     *
     */

    /*
     * Unit Test: Following is a local main method where we put some sample tests
     * you can use to verify that this class works properly; This code should only
     * be used except for debugging and testing purposes.
     *
     */
 
    public static void main(String [] args) {
        System.out.println("Unit tests for the BigInt class.");
        System.out.println();

        /* 
         * You should uncomment and run each test--one at a time--
         * after you build the corresponding methods of the class.
         *
         * Note that these unit tests are not complete and you should
         * think of additional tests that you should run to ensure
         * that all your methods work as expected.
         */

        /*
        System.out.println("Test 1: result should be 7");
        int[] a1 = { 0,0,0,0,0,0,0,0,0,0,0,0,0,1,2,3,4,5,6,7 };
        BigInt b1 = new BigInt(a1);
        System.out.println(b1.getNumSigDigits());
        System.out.println();
        
        System.out.println("Test 2: result should be 1234567");
        b1 = new BigInt(a1);
        System.out.println(b1);
        System.out.println();
        
        System.out.println("Test 3: result should be 0");
        int[] a2 = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
        BigInt b2 = new BigInt(a2);
        System.out.println(b2);
        System.out.println();
        
        System.out.println("Test 4: should throw an IllegalArgumentException");
        try {
            int[] a3 = { 0,0,0,0,23,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
            BigInt b3 = new BigInt(a3);
            System.out.println("Test failed.");
        } catch (IllegalArgumentException e) {
            System.out.println("Test passed.");
        } catch (Exception e) {
            System.out.println("Test failed: threw wrong type of exception.");
        }
        System.out.println();

        System.out.println("Test 5: result should be 1234567");
        b1 = new BigInt(1234567);
        System.out.println(b1);
        System.out.println();

        System.out.println("Test 6: result should be 0");
        b2 = new BigInt(0);
        System.out.println(b2);
        System.out.println();

        System.out.println("Test 7: should throw an IllegalArgumentException");
        try {
            BigInt b3 = new BigInt(-4);
            System.out.println("Test failed.");
        } catch (IllegalArgumentException e) {
            System.out.println("Test passed.");
        } catch (Exception e) {
            System.out.println("Test failed: threw wrong type of exception.");
        }
        System.out.println();

        System.out.println("Test 8: result should be 0");
        b1 = new BigInt(12375);
        b2 = new BigInt(12375);
        System.out.println(b1.compareTo(b2));
        System.out.println();

        System.out.println("Test 9: result should be -1");
        b2 = new BigInt(12378);
        System.out.println(b1.compareTo(b2));
        System.out.println();

        System.out.println("Test 10: result should be 1");
        System.out.println(b2.compareTo(b1));
        System.out.println();

        System.out.println("Test 11: result should be 0");
        b1 = new BigInt(0);
        b2 = new BigInt(0);
        System.out.println(b1.compareTo(b2));
        System.out.println();

        System.out.println("Test 12: result should be\n123456789123456789");
        int[] a4 = { 3,6,1,8,2,7,3,6,0,3,6,1,8,2,7,3,6 };
        int[] a5 = { 8,7,2,7,4,0,5,3,0,8,7,2,7,4,0,5,3 };
        BigInt b4 = new BigInt(a4);
        BigInt b5 = new BigInt(a5);
        BigInt sum = b4.add(b5);
        System.out.println(sum);
        System.out.println();

        System.out.println("Test 13: result should be\n123456789123456789");
        System.out.println(b5.add(b4));
        System.out.println();

        System.out.println("Test 14: result should be\n3141592653598");
        b1 = new BigInt(0);
        int[] a6 = { 3,1,4,1,5,9,2,6,5,3,5,9,8 };
        b2 = new BigInt(a6);
        System.out.println(b1.add(b2));
        System.out.println();

        System.out.println("Test 15: result should be\n10000000000000000000");
        int[] a19 = { 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9 };    // 19 nines!
        b1 = new BigInt(a19);
        b2 = new BigInt(1);
        System.out.println(b1.add(b2));
        System.out.println();

        System.out.println("Test 16: should throw an ArithmeticException");
        int[] a20 = { 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9 };  // 20 nines!
        try {
            b1 = new BigInt(a20);
            System.out.println(b1.add(b2));
        } catch (ArithmeticException e) {
            System.out.println("Test passed.");
        } catch (Exception e) {
            System.out.println("Test failed: threw wrong type of exception.");
        }
        System.out.println();

        System.out.println("Test 17: result should be 5670");
        b1 = new BigInt(135);
        b2 = new BigInt(42);
        BigInt product = b1.mul(b2);
        System.out.println(product);
        System.out.println();

        System.out.println("Test 18: result should be\n99999999999999999999");
        b1 = new BigInt(a20);   // 20 nines -- see above
        b2 = new BigInt(1);
        System.out.println(b1.mul(b2));
        System.out.println();

        System.out.println("Test 19: should throw an ArithmeticException");
        try {
            b1 = new BigInt(a20);
            b2 = new BigInt(2);
            System.out.println(b1.mul(b2));
        } catch (ArithmeticException e) {
            System.out.println("Test passed.");
        } catch (Exception e) {
            System.out.println("Test failed: threw wrong type of exception.");
        }
        System.out.println();
        */
    }
}