namespace Amphora.UnitTests
{
    public class SplitMix64Tests : UnitTestSharp.TestFixture
    {
        public class CtorTests : UnitTestSharp.TestFixture
        {
            public void StartsTheCounterAtTheSeed()
            {
                CheckEqual(1234567UL, new SplitMix64(1234567).State);
            }
        }

        public class NextUInt64Tests : UnitTestSharp.TestFixture
        {
            public void MatchesTheReferenceFromSeedZero()
            {
                var generator = new SplitMix64(0);

                CheckEqual(0xe220a8397b1dcdafUL, generator.NextUInt64());
                CheckEqual(0x6e789e6aa1b965f4UL, generator.NextUInt64());
                CheckEqual(0x06c45d188009454fUL, generator.NextUInt64());
                CheckEqual(0xf88bb8a8724c81ecUL, generator.NextUInt64());
            }

            public void MatchesTheReferenceFromSeed1234567()
            {
                var generator = new SplitMix64(1234567);

                CheckEqual(0x599ed017fb08fc85UL, generator.NextUInt64());
                CheckEqual(0x2c73f08458540fa5UL, generator.NextUInt64());
                CheckEqual(0x883ebce5a3f27c77UL, generator.NextUInt64());
                CheckEqual(0x3fbef740e9177b3fUL, generator.NextUInt64());
            }

            public void AdvancesTheCounterByTheIncrement()
            {
                var generator = new SplitMix64(5);

                generator.NextUInt64();

                CheckEqual(5 + SplitMix64.Increment, generator.State);
            }

            public void TheCounterWrapsPastTheTop()
            {
                var generator = new SplitMix64(ulong.MaxValue);

                generator.NextUInt64();

                CheckEqual(SplitMix64.Increment - 1, generator.State);
            }
        }

        public class NextUInt32Tests : UnitTestSharp.TestFixture
        {
            public void IsTheUpperHalfOfTheNext64BitDraw()
            {
                var generator = new SplitMix64(0);

                CheckEqual(0xe220a839U, generator.NextUInt32());
                CheckEqual(0x6e789e6aU, generator.NextUInt32());
            }
        }
    }
}