namespace Amphora.UnitTests
{
    public class RandTests : UnitTestSharp.TestFixture
    {
        public class SeedCtorTests : UnitTestSharp.TestFixture
        {
            public void DrawsWhatSfc64DrawsFromTheSameSeed()
            {
                var rand = new Rand(42);
                var reference = new Sfc64(42);

                CheckEqual(reference.NextUInt64(), rand.NextUInt64());
                CheckEqual(reference.NextUInt64(), rand.NextUInt64());
            }

            public void DifferentSeeds_DrawDifferentNumbers()
            {
                CheckTrue(new Rand(1).NextUInt64() != new Rand(2).NextUInt64());
            }
        }

        public class GeneratorCtorTests : UnitTestSharp.TestFixture
        {
            public void ResumesFromTheGeneratorsState()
            {
                var generator = new Sfc64(state0: 1, state1: 2, state2: 3, counter: 4);
                var rand = new Rand(generator);

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

        public class SpawnTests : UnitTestSharp.TestFixture
        {
            public void IsSeededFromTheNext64BitDraw()
            {
                var parent = new Rand(42);
                var reference = new Sfc64(42);
                var expected = new Rand(reference.NextUInt64());

                Rand spawned = parent.Spawn();

                CheckEqual(expected.NextUInt64(), spawned.NextUInt64());
                CheckEqual(expected.NextUInt64(), spawned.NextUInt64());
            }

            public void CostsTheParentOneDraw()
            {
                var parent = new Rand(42);
                var reference = new Sfc64(42);
                reference.NextUInt64();

                parent.Spawn();

                CheckEqual(reference.NextUInt64(), parent.NextUInt64());
            }

            public void SuccessiveSpawns_DrawDifferentNumbers()
            {
                var parent = new Rand(42);

                CheckTrue(parent.Spawn().NextUInt64() != parent.Spawn().NextUInt64());
            }
        }

        public class SharingTests : UnitTestSharp.TestFixture
        {
            public void TwoHoldersOfOneRand_DrawFromOneStream()
            {
                var shared = new Rand(42);
                Rand otherHolder = shared;
                var reference = new Sfc64(42);

                CheckEqual(reference.NextUInt64(), shared.NextUInt64());
                CheckEqual(reference.NextUInt64(), otherHolder.NextUInt64());
                CheckEqual(reference.NextUInt64(), shared.NextUInt64());
            }
        }
    }
}