using System;

namespace Gs2.Unity.Gs2StateMachine.Local
{
    public class SharedRandom
    {
        private const uint M = 10;

        private static uint[] RoundFunction(uint[] x, uint[] k)
        {
            const uint rand0 = 0xD2511F53;
            const uint rand1 = 0xCD9E8D57;

            return new[]
            {
                rand0 * x[0] ^ x[1] ^ k[0],
                rand1 * x[1] ^ k[1],
            };
        }

        private static uint[] KeySchedule(uint[] k)
        {
            const uint randWeylConstant = 0x9E3779B9;
            const uint randWeylIncrement = 0xBB67AE85;

            k[0] += randWeylConstant;
            k[1] += randWeylIncrement;
            return k;
        }

        private readonly uint[] _seed;
        private readonly uint[] _counter;

        public SharedRandom(uint seed, uint category)
        {
            this._seed = new uint[] { seed, category };
            this._counter = new uint[] { 0, 0 };
        }

        public void SetCounter(uint counter)
        {
            this._counter[0] = counter;
        }

        public uint Next()
        {
            var c = (uint[])this._counter.Clone();
            var s = (uint[])this._seed.Clone();
            for (uint i = 0; i < M; i++)
            {
                c = RoundFunction(c, s);
                s = KeySchedule(s);
            }
            this._counter[0]++;
            if (this._counter[0] == 0)
            {
                this._counter[1]++;
            }
            return c[0];
        }
    }
}