using System;

namespace SoFii {
    public static class RNG {
        private static object Lock { get; } = new object();
        private static Random NormalRandom { get; } = new Random();

        public static int Next() {
            lock(Lock)
                return NormalRandom.Next();
        }

        public static int Next(int max) {
            lock(Lock)
                return NormalRandom.Next(max);
        }

        public static int Next(int min, int max) {
            lock(Lock)
                return NormalRandom.Next(min, max);
        }

        public static void NextBytes(byte[] buffer) {
            lock(Lock)
                NormalRandom.NextBytes(buffer);
        }

        public static void Shuffle<T>(T[] arr) {
            if(arr is null)
                throw new ArgumentNullException(nameof(arr));

            lock(Lock) {
                int n = arr.Length;
                while(n > 1) {
                    int k = Next(n--);
                    T tmp = arr[n];
                    arr[n] = arr[k];
                    arr[k] = tmp;
                }
            }
        }
    }
}