package api;

/** Class to simplify arithmetical operations, improved version to compute

 * the sum for ranges, but only if one uses the new constructor to indicate

 * need for new version.

 *

 * @author Jaroslav Tulach <jtulach@netbeans.org>

 * @version 2.0

 */

// BEGIN: design.composition.arith2.0.enum

public class Arithmetica {

    private final Version version;

    public enum Version { VERSION_1_0, VERSION_2_0 }

    public Arithmetica() {

        this(Version.VERSION_1_0);

    }

    public Arithmetica(Version version) {

        this.version = version;

    }

    public int sumRange(int from, int to) {

        switch (version) {

            case VERSION_1_0:

                return sumRange1(from, to);

            case VERSION_2_0:

                return sumRange2(from, to);

            default:

                throw new IllegalStateException();

        }

    }

// FINISH: design.composition.arith2.0.enum

    public int sumTwo(int one, int second) {

        return one + second;

    }

    public int sumAll(int... numbers) {

        if (numbers.length == 0) {

            return 0;

        }

        int sum = numbers[0];

        for (int i = 1; i < numbers.length; i++) {

            sum = sumTwo(sum, numbers[i]);

        }

        return sum;

    }

    private int sumRange1(int from, int to) {

        int len = to - from;

        if (len < 0) {

            len = -len;

            from = to;

        }

        int[] array = new int[len + 1];

        for (int i = 0; i <= len; i++) {

            array[i] = from + i;

        }

        return sumAll(array);

    }

    private int sumRange2(int from, int to) {

        return (from + to) * (Math.abs(to - from) + 1) / 2;

    }

}