namespace Amphora.UnitTests
{
    public class Sfc64Tests : UnitTestSharp.TestFixture
    {
        public static Sfc64 OneTwoThreeFour()
        {
            return new Sfc64(state0: 1, state1: 2, state2: 3, counter: 4);
        }

        public class SeedCtorTests : UnitTestSharp.TestFixture
        {
            public void MatchesTheReferenceSeededFrom42()
            {
                var generator = new Sfc64(42);

                CheckEqual(0x74445bc8d8c88b03UL, generator.NextUInt64());
                CheckEqual(0xc2f7e2538f4899c6UL, generator.NextUInt64());
                CheckEqual(0x05d131045418b46bUL, generator.NextUInt64());
                CheckEqual(0x5210a499c6b5a485UL, generator.NextUInt64());
            }

            public void LeavesTheCounterPastTheSeedingRounds()
            {
                CheckEqual(1UL + Sfc64.SeedingRounds, new Sfc64(42).Counter);
            }
        }

        public class StateCtorTests : UnitTestSharp.TestFixture
        {
            public void KeepsTheStateAsGiven()
            {
                Sfc64 generator = OneTwoThreeFour();

                CheckEqual(1UL, generator.State0);
                CheckEqual(2UL, generator.State1);
                CheckEqual(3UL, generator.State2);
                CheckEqual(4UL, generator.Counter);
            }
        }

        public class NextUInt64Tests : UnitTestSharp.TestFixture
        {
            public void MatchesTheReference()
            {
                Sfc64 generator = OneTwoThreeFour();

                CheckEqual(0x0000000000000007UL, generator.NextUInt64());
                CheckEqual(0x0000000000000022UL, generator.NextUInt64());
                CheckEqual(0x000000001b000060UL, generator.NextUInt64());
                CheckEqual(0x001b00005a036178UL, generator.NextUInt64());
                CheckEqual(0x005a03626407ff9aUL, generator.NextUInt64());
                CheckEqual(0x03570803af636aa4UL, generator.NextUInt64());
                CheckEqual(0x27cca0434a7b0461UL, generator.NextUInt64());
                CheckEqual(0x647c3edbad20110dUL, generator.NextUInt64());
            }

            public void TheCounterKeepsTheAllZeroStateMoving()
            {
                var generator = default(Sfc64);

                CheckEqual(0UL, generator.NextUInt64());
                CheckEqual(1UL, generator.NextUInt64());
            }
        }

        public class NextUInt32Tests : UnitTestSharp.TestFixture
        {
            public void IsTheUpperHalfOfTheNext64BitDraw()
            {
                Sfc64 generator = OneTwoThreeFour();
                for (int i = 0; i < 6; i++)
                {
                    generator.NextUInt64();
                }

                CheckEqual(0x27cca043U, generator.NextUInt32());
                CheckEqual(0x647c3edbU, generator.NextUInt32());
            }
        }
    }
}