namespace SortingVisualization.Algorithms {
    public class Mergesort : SortingAlgorithm {
        public override string GetAlgorithmName() => "Mergesort";

        public override void Sort(ref DataSet set) {
            Simulate(ref set);
            System.Console.WriteLine("Doing {0}...", this.GetAlgorithmName());
            MergeSort(ref set, 0, set.Size - 1);
            System.Console.WriteLine("{0} complete!", this.GetAlgorithmName());
            if (!set.SimulateMode)
                set.FinalizeVideo();
        }
        public static void MergeSort(ref DataSet set, int l, int r) {
            if (l < r) {
                int mid = (l / 2) + (r / 2);
                MergeSort(ref set, l, mid);
                MergeSort(ref set, mid + 1, r);
                Merge(ref set, l, mid, r);
            }
        }

        private static void Merge(ref DataSet set, int l, int m, int r) {
            int left = l;
            int right = m + 1;
            int[] tmp = new int[(r - l) + 1];
            int tmpIndex = 0;

            while ((left <= m) && (right <= r)) {
                if (set.LessThan(left, right)) {
                    tmp[tmpIndex] = set.ReadOperation(left);
                    left++;
                } else {
                    tmp[tmpIndex] = set.ReadOperation(right);
                    right++;
                }
                tmpIndex++;
            }

            while (left <= m) {
                tmp[tmpIndex] = set.ReadOperation(left);
                left++;
                tmpIndex++;
            }

            while (right <= r) {
                tmp[tmpIndex] = set.ReadOperation(right);
                right++;
                tmpIndex++;
            }

            for (int i = 0; i < tmp.Length; i++) {
                set.WriteOperation(l + i, tmp[i]);
            }

        }
    }
}