/*
 * ArrayObjecr.java
 *
 * A collection of instance methods for working with arrays.
 * 
 *
 * CS112
 *
 */

import java.util.*;

public class ArrayObject {
    private static final int DEFAULT_SIZE = 20;
    private int [] values;

    public ArrayObject() {
        values = new int[DEFAULT_SIZE];
    }

    public ArrayObject( int[] arr ) {
        if (arr == null)
            throw new IllegalArgumentException();

	// Note that we are explicitly assigning the instance
	// variable values to reference the input array
        values = arr;
    }

    /*
     * square - takes an array of integers and squares each
     * element of the array.
     */
    public void square() {

        for (int i = 0; i < values.length; i++) {
            values[i] = values[i] * values[i];
        }
    }

    /*
     * shiftLeft - takes an array of integers and shifts each element
     * one position to the left. The last element of the array becomes 0,
     * and the original first element is returned.
     */
    public int shiftLeft() {

        // save the first value so we don't lose it
        int first = values[0];

        // do the shifting
        for (int i = 0; i < values.length - 1; i++) {
            values[i] = values[i + 1];
        }

        values[values.length - 1] = 0;

        return first;
    }

    /*
     * equals - takes two arrays and determines if the arrays
     * are equivalent.
     *
     * version 1: use a boolean variable for the return value,
     * and adjust it as needed based on the two arrays.
     */
    public boolean equals(ArrayObject b) {
        boolean isEqual = false;

        // Are a and b referencing the same physical array?
        // Note will also return true if a and b are null.
        if (this == b)
            isEqual = true;
        else if (b != null) {
            // If either array is null then they are not equal
            // so no need to check further, only continue
            // checking if both a and b are referencing a valid array

            // if the arrays are not of the same size
            // there is no need to check the contents,
            // as they cannot be equivalent.
            //
            if (values.length == b.values.length) {
                isEqual = true; // assume they are equivalent

                // check each element in each array, and stop
                // the loop at the first element that does not match
                for (int i = 0; (i < values.length) && isEqual; i++) {
                    if (values[i] != b.values[i])
                        isEqual = false;
                }
            }
        }

        return isEqual;
    }

    /*
     * replace - this method replaces all occurences of
     * val2 in the array with val1. The method returns the
     * number of occurences.
     */
    public int replace(int val1, int val2) {

        int replaced = 0; // make sure to initialize to zero

        for (int i = 0; i < values.length; i++) {
            // Note that we are comparing elements of the array
            // and because the elements are of type int can use ==
            if (values[i] == val1) {
                values[i] = val2;
                replaced++;
            }
        }

        return replaced;
    }

    public String toString() {
	    return Arrays.toString(values);
    }

    /*
     * main -
     *
     * sample unit test method used to test each of the methods in this program
     * class.
     */
    public static void main(String[] argv) {
        // Note the use of separate scopes to reuse variable names.

        // Test equals and interChange
            int[] a = { 1, 2, 3, 4, 5 };
            int[] b = { 5, 4, 3, 2, 1 };
            int[] c = { 5, 4, 3, 2, 1 };

	    ArrayObject aObj_a = new ArrayObject(a);
            ArrayObject aObj_b = new ArrayObject(b);
            ArrayObject aObj_c = new ArrayObject(c);

            System.out.println("test 1 for toString: " + Arrays.toString(a) + " <==> " + aObj_a );
            System.out.println("test 1 for toString: " + Arrays.toString(b) + " <==> " + aObj_b );
            System.out.println("test 1 for toString: " + Arrays.toString(c) + " <==> " + aObj_c );


            System.out.println("test 1 for equals: " + aObj_a.equals( aObj_c ) );
            System.out.println("test 2 for equals: " + aObj_b.equals( aObj_c ) );

	    aObj_c.square();
            System.out.println("test 1 for square: " + aObj_c  );
    }
}