using FluentAssertions;
using PerfectNumbers.Core.Gpu;
using PerfectNumbers.Core.Gpu.Accelerators;
using Xunit;

namespace PerfectNumbers.Core.Tests;

public class PrimeTesterIsPrimeTests
{
	[Theory]
	[Trait("Category", "Fast")]
	// EvenPerfectBitScanner never routes the tiny values anymore; keep coverage focused on the admissible range handled by production scans so the guards in PrimeTester stay commented out without breaking validation.
	[InlineData(7UL, true)]
	[InlineData(9UL, false)]
	[InlineData(11UL, true)]
	[InlineData(13UL, true)]
	[InlineData(21UL, false)]
	[InlineData(97UL, true)]
	[InlineData(133UL, false)]
	[InlineData(137UL, true)]
	[InlineData(143UL, false)]
	[InlineData(199UL, true)]
	[InlineData(209UL, false)]
	[InlineData(403UL, false)]
	[InlineData(341UL, false)]
	public void IsPrime_returns_expected_results(ulong n, bool expected)
	{
		var tester = new PrimeTester();

		PrimeTester.IsPrimeCpu(n).Should().Be(expected);
	}

	[Theory]
	[Trait("Category", "Fast")]
	[InlineData(139UL, true)]
	[InlineData(189UL, false)]
	[InlineData(193UL, true)]
	[InlineData(279UL, false)]
	public void IsPrimeGpu_uses_residue_specific_tables(ulong n, bool expected)
	{
		var tester = new PrimeTester();

		var gpu = PrimeOrderCalculatorAccelerator.Rent(1);
		try
		{
			PrimeTester.IsPrimeGpu(gpu, n).Should().Be(expected);
		}
		finally
		{
			PrimeOrderCalculatorAccelerator.Return(gpu);
		}
	}

	[Fact]
	[Trait("Category", "Fast")]
	public void IsPrimeGpu_falls_back_to_cpu_when_forced()
	{
		var tester = new PrimeTester();
		PrimeTester.IsPrimeCpu(137UL).Should().BeTrue();
		PrimeTester.IsPrimeCpu(341UL).Should().BeFalse();
	}

	[Fact]
	[Trait("Category", "Fast")]
	public void IsPrimeGpu_handles_parallel_calls_for_known_primes()
	{
		GpuPrimeWorkLimiter.SetLimit(64);
		PrimeTester.GpuBatchSize = 256_000;

		ulong[] primes = [107UL, 127UL, 521UL, 607UL];
		var results = new bool[primes.Length];

		var testers = new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true);
		var gpu = PrimeOrderCalculatorAccelerator.Rent(1);
		try
		{
			Parallel.For(0, primes.Length, i =>
			{
				results[i] = PrimeTester.IsPrimeGpu(gpu, primes[i]);
			});

			results.Should().AllBeEquivalentTo(true);

			Parallel.For(0, Environment.ProcessorCount * 16, _ =>
			{
				foreach (ulong prime in primes)
				{
					PrimeTester.IsPrimeGpu(gpu, prime).Should().BeTrue();
				}
			});
		}
		finally
		{
			PrimeOrderCalculatorAccelerator.Return(gpu);
		}
	}
}