package org.apidesign.math;

import org.apidesign.math.Arithmetica;

import org.apidesign.runtime.check.RuntimeCheck;

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

 * the sum for ranges, but only if the virtual machine is configured to

 * run in incompatible mode.

 *

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

 * @version 2.0

 */

public class Arithmetica {

    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;

    }

    public int sumRange(int from, int to) {

        if (calledByV2AwareLoader()) {

            return sumRange2(from, to);

        } else {

            return sumRange1(from, to);

        }

    }

    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;

    }

    private static boolean calledByV2AwareLoader() {

        // BEGIN: design.composition.arith2.6.runtime

        StackTraceElement[] arr = Thread.currentThread().getStackTrace();

        ClassLoader myLoader = Arithmetica.class.getClassLoader();

        for (int i = 0; i < arr.length; i++) {

            ClassLoader caller = arr[i].getClass().getClassLoader();

            if (myLoader == caller) {

                continue;

            }

            if (RuntimeCheck.requiresAtLeast("2.6", "api.Arithmetica", caller)) {

                return true;

            }

            return false;

        }

        return true;

        // END: design.composition.arith2.6.runtime

    }

}