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

// NOTE fisher-yates, http://bost.ocks.org/mike/algorithms/
/**
 * Returns copy of an array shuffled using Fisher-Yates.
 */
Sorter.prototype.shuffle = function(arr) {
    var result = Object.create(arr);
    var n = result.length, t, i;
    while (n) {
        i = Math.random() * n-- | 0; // 0 ≤ i < n
        t = result[n];
        result[n] = result[i];
        result[i] = t;
    }
    return result;
};

/**
 *
 */
Sorter.prototype.generate = function(n) {
    var arr = [];
    var v;
    for (var i = 0; i < n; i++) {
        v = Math.floor(i * 255 / n);
        arr.push({
            value: v,
            fill: `rgb(0, 0, ${v})`
        });
    };

    return arr;
};

/**
 *
 */
Sorter.prototype.swap = function(arr, i, j) {
    // console.info(`swapping ${arr[i].value} and ${arr[j].value}`)
    var tmp = arr[i];
    arr[i] = arr[j];
    arr[j] = tmp;
};

/**
 *
 */
Sorter.prototype.sort = function(instruction) {
    throw new Error('Sorter.sort() method override required.');
};

/**
 *
 */
Sorter.prototype.addInstruction = function(instruction) {
    throw new Error('Sorter.addInstruction() method override required.');
};