using System;

namespace Amphora.UnitTests
{
    public class Xoshiro128PlusPlusTests : UnitTestSharp.TestFixture
    {
        public static Xoshiro128PlusPlus OneTwoThreeFour()
        {
            return new Xoshiro128PlusPlus(state0: 1, state1: 2, state2: 3, state3: 4);
        }

        public class SeedCtorTests : UnitTestSharp.TestFixture
        {
            public void FillsTheStateWithTwoSplitMix64DrawsLowerHalfFirst()
            {
                var seeder = new SplitMix64(42);
                ulong first = seeder.NextUInt64();
                ulong second = seeder.NextUInt64();

                var generator = new Xoshiro128PlusPlus(42);

                CheckEqual((uint)first, generator.State0);
                CheckEqual((uint)(first >> 32), generator.State1);
                CheckEqual((uint)second, generator.State2);
                CheckEqual((uint)(second >> 32), generator.State3);
            }

            public void MatchesTheReferenceSeededFrom42()
            {
                var generator = new Xoshiro128PlusPlus(42);

                CheckEqual(0x9d9452c1U, generator.NextUInt32());
                CheckEqual(0x6909d440U, generator.NextUInt32());
                CheckEqual(0x6148a68fU, generator.NextUInt32());
                CheckEqual(0x54829a5bU, generator.NextUInt32());
            }
        }

        public class StateCtorTests : UnitTestSharp.TestFixture
        {
            public void KeepsTheStateAsGiven()
            {
                Xoshiro128PlusPlus generator = OneTwoThreeFour();

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

            public void AcceptsOneNonzeroWord()
            {
                var generator = new Xoshiro128PlusPlus(state0: 0, state1: 0, state2: 1, state3: 0);

                CheckEqual(1U, generator.State2);
            }

            public void RejectsAnAllZeroState()
            {
                CheckThrow(typeof(ArgumentException));
                new Xoshiro128PlusPlus(state0: 0, state1: 0, state2: 0, state3: 0);
            }
        }

        public class NextUInt32Tests : UnitTestSharp.TestFixture
        {
            public void MatchesTheReference()
            {
                Xoshiro128PlusPlus generator = OneTwoThreeFour();

                CheckEqual(0x00000281U, generator.NextUInt32());
                CheckEqual(0x00180387U, generator.NextUInt32());
                CheckEqual(0xc0183387U, generator.NextUInt32());
                CheckEqual(0xd1ae3b02U, generator.NextUInt32());
                CheckEqual(0x31e2310aU, generator.NextUInt32());
                CheckEqual(0xfd275ab0U, generator.NextUInt32());
                CheckEqual(0xe67f7cecU, generator.NextUInt32());
                CheckEqual(0x50d07f0fU, generator.NextUInt32());
            }

            public void TheDefaultValueDrawsOnlyZeros()
            {
                var generator = default(Xoshiro128PlusPlus);

                CheckEqual(0U, generator.NextUInt32());
                CheckEqual(0U, generator.NextUInt32());
            }
        }

        public class NextUInt64Tests : UnitTestSharp.TestFixture
        {
            public void PutsTheFirst32BitDrawInTheUpperHalf()
            {
                Xoshiro128PlusPlus generator = OneTwoThreeFour();

                CheckEqual(0x0000028100180387UL, generator.NextUInt64());
                CheckEqual(0xc0183387d1ae3b02UL, generator.NextUInt64());
            }
        }

        public class JumpTests : UnitTestSharp.TestFixture
        {
            public void MatchesTheReferenceDrawsAfterward()
            {
                Xoshiro128PlusPlus generator = OneTwoThreeFour();

                generator.Jump();

                CheckEqual(0xba8c0ddcU, generator.NextUInt32());
                CheckEqual(0x06a228ceU, generator.NextUInt32());
                CheckEqual(0x4506c342U, generator.NextUInt32());
                CheckEqual(0x6d64b9f6U, generator.NextUInt32());
            }
        }

        public class LongJumpTests : UnitTestSharp.TestFixture
        {
            public void MatchesTheReferenceDrawsAfterward()
            {
                Xoshiro128PlusPlus generator = OneTwoThreeFour();

                generator.LongJump();

                CheckEqual(0x99cc2935U, generator.NextUInt32());
                CheckEqual(0x7f4f19b6U, generator.NextUInt32());
                CheckEqual(0x09b914e1U, generator.NextUInt32());
                CheckEqual(0x6de722e8U, generator.NextUInt32());
            }
        }
    }
}