/**
 *
 */
var Sorter = function() {};
Sorter.prototype.instructions = [];

// NOTE fisher-yates, http://bost.ocks.org/mike/algorithms/
/**
 *
 */
Sorter.prototype.shuffle = function(arr) {
    var n = arr.length, t, i;
    while (n) {
        i = Math.random() * n-- | 0; // 0 ≤ i < n
        t = arr[n];
        arr[n] = arr[i];
        arr[i] = t;
    }
    return arr;
};

/**
 *
 */
Sorter.prototype.addInstruction = function(operation, left, right, pivot) {
    this.instructions.push({
        operation: operation,
        left: left,
        right: right,
        pivot: pivot
    });
};

// NOTE adds to an instruction set
/**
 *
 */
Sorter.prototype.quicksort = function(arr, start, end) {
    if (end - start <= 0) {
        this.addInstruction('single', start, end, null);
        return this.visualizer;
    }

    var left = start;
    var right = end;

    var pivot = Math.floor((right + left) / 2);
    var pivotval = arr[pivot].val;
    var tmp;

    this.addInstruction('init', left, right, pivot);

    while (left <= right) {
        while (arr[left].val < pivotval) {
            left++;
            this.addInstruction('inc-left', left, right, pivot);
        }

        while (arr[right].val > pivotval) {
            right--;
            this.addInstruction('dec-right', left, right, pivot);
        }

        if (left <= right) {
            tmp = arr[left];
            arr[left] = arr[right];
            arr[right] = tmp;

            this.addInstruction('swap', left, right, pivot);

            left++;
            right--;
            this.addInstruction('swap-inc-dec', left, right, pivot);
        }
    }

    this.quicksort(arr, start, right);
    this.quicksort(arr, left, end);
};