namespace Amphora.UnitTests
{
    public class Xoshiro256PlusTests : UnitTestSharp.TestFixture
    {
        public class SeedCtorTests : UnitTestSharp.TestFixture
        {
            public void FillsTheStateFromSplitMix64()
            {
                var generator = new Xoshiro256Plus(42);
                var fromWords = new Xoshiro256Plus(0xbdd732262feb6e95UL, 0x28efe333b266f103UL,
                    0x47526757130f9f52UL, 0x581ce1ff0e4ae394UL);

                CheckEqual(fromWords.NextUInt64(), generator.NextUInt64());
            }

            public void MatchesTheRecurrenceFromSeed42()
            {
                var generator = new Xoshiro256Plus(42);

                CheckEqual(0x15f414253e365229UL, generator.NextUInt64());
                CheckEqual(0x4f771f08f4211387UL, generator.NextUInt64());
                CheckEqual(0x100492bd8828891eUL, generator.NextUInt64());
                CheckEqual(0x4e743fce495374aeUL, generator.NextUInt64());
            }
        }

        public class StateCtorTests : UnitTestSharp.TestFixture
        {
            public void StartsFromTheGivenWords()
            {
                var generator = new Xoshiro256Plus(1, 2, 3, 4);

                CheckEqual(0x0000000000000005UL, generator.NextUInt64());
                CheckEqual(0x0000c00000000007UL, generator.NextUInt64());
            }
        }

        public class NextUInt64Tests : UnitTestSharp.TestFixture
        {
            public void MatchesTheRecurrenceFromStateOneTwoThreeFour()
            {
                var generator = new Xoshiro256Plus(1, 2, 3, 4);

                CheckEqual(0x0000000000000005UL, generator.NextUInt64());
                CheckEqual(0x0000c00000000007UL, generator.NextUInt64());
                CheckEqual(0x0000c00018000007UL, generator.NextUInt64());
                CheckEqual(0x8001600018040302UL, generator.NextUInt64());
                CheckEqual(0x8061900024040305UL, generator.NextUInt64());
                CheckEqual(0xc0617014120f0583UL, generator.NextUInt64());
            }
        }

        public class NextUInt32Tests : UnitTestSharp.TestFixture
        {
            public void IsTheUpperHalfOfTheNext64BitDraw()
            {
                var generator = new Xoshiro256Plus(1, 2, 3, 4);
                for (int i = 0; i < 4; i++)
                {
                    generator.NextUInt64();
                }

                CheckEqual(0x80619000U, generator.NextUInt32());
                CheckEqual(0xc0617014U, generator.NextUInt32());
            }
        }
    }
}