using System;

namespace Amphora.UnitTests
{
    public class Xoshiro256PlusPlusTests : UnitTestSharp.TestFixture
    {
        public static Xoshiro256PlusPlus OneTwoThreeFour()
        {
            return new Xoshiro256PlusPlus(state0: 1, state1: 2, state2: 3, state3: 4);
        }

        public class SeedCtorTests : UnitTestSharp.TestFixture
        {
            public void FillsTheStateWithSplitMix64Draws()
            {
                var seeder = new SplitMix64(42);
                var generator = new Xoshiro256PlusPlus(42);

                CheckEqual(seeder.NextUInt64(), generator.State0);
                CheckEqual(seeder.NextUInt64(), generator.State1);
                CheckEqual(seeder.NextUInt64(), generator.State2);
                CheckEqual(seeder.NextUInt64(), generator.State3);
            }

            public void MatchesTheReferenceSeededFrom42()
            {
                var generator = new Xoshiro256PlusPlus(42);

                CheckEqual(0xd0764d4f4476689fUL, generator.NextUInt64());
                CheckEqual(0x519e4174576f3791UL, generator.NextUInt64());
                CheckEqual(0xfbe07cfb0c24ed8cUL, generator.NextUInt64());
                CheckEqual(0xb37d9f600cd835b8UL, generator.NextUInt64());
            }

            public void MatchesTheReferenceSeededFromZero()
            {
                var generator = new Xoshiro256PlusPlus(0);

                CheckEqual(0x53175d61490b23dfUL, generator.NextUInt64());
                CheckEqual(0x61da6f3dc380d507UL, generator.NextUInt64());
                CheckEqual(0x5c0fdf91ec9a7bfcUL, generator.NextUInt64());
                CheckEqual(0x02eebf8c3bbe5e1aUL, generator.NextUInt64());
            }
        }

        public class StateCtorTests : UnitTestSharp.TestFixture
        {
            public void KeepsTheStateAsGiven()
            {
                Xoshiro256PlusPlus generator = OneTwoThreeFour();

                CheckEqual(1UL, generator.State0);
                CheckEqual(2UL, generator.State1);
                CheckEqual(3UL, generator.State2);
                CheckEqual(4UL, generator.State3);
            }

            public void AcceptsOneNonzeroWord()
            {
                var generator = new Xoshiro256PlusPlus(state0: 0, state1: 0, state2: 0, state3: 1);

                CheckEqual(1UL, generator.State3);
            }

            public void RejectsAnAllZeroState()
            {
                CheckThrow(typeof(ArgumentException));
                new Xoshiro256PlusPlus(state0: 0, state1: 0, state2: 0, state3: 0);
            }
        }

        public class NextUInt64Tests : UnitTestSharp.TestFixture
        {
            public void MatchesTheReference()
            {
                Xoshiro256PlusPlus generator = OneTwoThreeFour();

                CheckEqual(0x0000000002800001UL, generator.NextUInt64());
                CheckEqual(0x0000000003800067UL, generator.NextUInt64());
                CheckEqual(0x000cc00003800067UL, generator.NextUInt64());
                CheckEqual(0x000cc201994400b2UL, generator.NextUInt64());
                CheckEqual(0x8012a2019ac433cdUL, generator.NextUInt64());
                CheckEqual(0x8a69978acdee33baUL, generator.NextUInt64());
                CheckEqual(0xc271134733154abdUL, generator.NextUInt64());
                CheckEqual(0xac2ba09179169e97UL, generator.NextUInt64());
            }

            public void TheDefaultValueDrawsOnlyZeros()
            {
                var generator = default(Xoshiro256PlusPlus);

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

        public class NextUInt32Tests : UnitTestSharp.TestFixture
        {
            public void IsTheUpperHalfOfTheNext64BitDraw()
            {
                Xoshiro256PlusPlus generator = OneTwoThreeFour();
                for (int i = 0; i < 4; i++)
                {
                    generator.NextUInt64();
                }

                CheckEqual(0x8012a201U, generator.NextUInt32());
                CheckEqual(0x8a69978aU, generator.NextUInt32());
            }
        }

        public class JumpTests : UnitTestSharp.TestFixture
        {
            public void MatchesTheReferenceState()
            {
                Xoshiro256PlusPlus generator = OneTwoThreeFour();

                generator.Jump();

                CheckEqual(0x8c7a153956b5f3d1UL, generator.State0);
                CheckEqual(0x701f1a713401d85eUL, generator.State1);
                CheckEqual(0x6527f66a65469085UL, generator.State2);
                CheckEqual(0x8386b786c4408050UL, generator.State3);
            }

            public void MatchesTheReferenceDrawsAfterward()
            {
                Xoshiro256PlusPlus generator = OneTwoThreeFour();

                generator.Jump();

                CheckEqual(0xec879073673df437UL, generator.NextUInt64());
                CheckEqual(0x20d212a39aca1eaaUL, generator.NextUInt64());
                CheckEqual(0xc19d712a27e40f57UL, generator.NextUInt64());
                CheckEqual(0x6ff0e08dc71026a1UL, generator.NextUInt64());
            }
        }

        public class LongJumpTests : UnitTestSharp.TestFixture
        {
            public void MatchesTheReferenceDrawsAfterward()
            {
                Xoshiro256PlusPlus generator = OneTwoThreeFour();

                generator.LongJump();

                CheckEqual(0xb5c4ea370b330bf5UL, generator.NextUInt64());
                CheckEqual(0x5173cc693c0fa533UL, generator.NextUInt64());
                CheckEqual(0x1dc5df0151f7b491UL, generator.NextUInt64());
                CheckEqual(0xe7b055cfeabc4661UL, generator.NextUInt64());
            }
        }
    }
}