/**
 *
 */
var MergeSort = function() {};

MergeSort.prototype = Object.create(Sorter.prototype);

/**
 *
 */
MergeSort.prototype.sort = function(arr, start, end) {
    if (arr.length === 0) {
        return arr;
    }

    if (start === end) {
        this.addInstruction('single', start);
        return new Array(arr[start]);
    }

    var mid = start + Math.floor((end - start) / 2);

    var arr1 = this.sort(arr, start, mid);
    var arr2 = this.sort(arr, mid + 1, end);

    var result = this.merge(arr1, arr2);

    return result;
};

/**
 *
 */
MergeSort.prototype.merge = function(arr1, arr2) {
    var result = [];

    while (arr1.length > 0 || arr2.length > 0) {
        if (arr1.length === 0) {
            result.push(arr2.shift());
        }
        else if (arr2.length === 0) {
            result.push(arr1.shift());
        }
        else if (arr1[0].value <= arr2[0].value) {
            result.push(arr1.shift());
        }
        else {
            result.push(arr2.shift());
        }
    }

    return result;
};