FictionArchive/FictionArchive.Service.TranslationService.Tests/Resilience/TranslationResiliencePipelineTests.cs

using DeepL;
using FictionArchive.Service.TranslationService.Services.Resilience;
using FluentAssertions;
using Polly;
using Xunit;

namespace FictionArchive.Service.TranslationService.Tests.Resilience;

public class TranslationResiliencePipelineTests
{
    [Fact]
    public async Task RetriesTransientHttpRequestException_ThenSucceeds()
    {
        var pipeline = TranslationResiliencePipeline.Build();
        var attempts = 0;

        var result = await pipeline.ExecuteAsync(async _ =>
        {
            attempts++;
            if (attempts < 3)
            {
                throw new HttpRequestException("transient");
            }
            return await ValueTask.FromResult("ok");
        });

        attempts.Should().Be(3);
        result.Should().Be("ok");
    }

    [Fact]
    public async Task RetriesDeepLConnectionException()
    {
        var pipeline = TranslationResiliencePipeline.Build();
        var attempts = 0;

        var result = await pipeline.ExecuteAsync(async _ =>
        {
            attempts++;
            if (attempts < 2)
            {
                throw new ConnectionException("transient", new HttpRequestException("inner"));
            }
            return await ValueTask.FromResult("ok");
        });

        attempts.Should().Be(2);
        result.Should().Be("ok");
    }

    [Fact]
    public async Task RetriesDeepLTooManyRequestsException()
    {
        var pipeline = TranslationResiliencePipeline.Build();
        var attempts = 0;

        var result = await pipeline.ExecuteAsync(async _ =>
        {
            attempts++;
            if (attempts < 2)
            {
                throw new TooManyRequestsException("rate limited");
            }
            return await ValueTask.FromResult("ok");
        });

        attempts.Should().Be(2);
        result.Should().Be("ok");
    }

    [Fact]
    public async Task DoesNotRetryNonTransientException()
    {
        var pipeline = TranslationResiliencePipeline.Build();
        var attempts = 0;

        var act = async () => await pipeline.ExecuteAsync(async _ =>
        {
            attempts++;
            throw new ArgumentException("permanent");
#pragma warning disable CS0162
            return await ValueTask.FromResult("never");
#pragma warning restore CS0162
        });

        await act.Should().ThrowAsync<ArgumentException>();
        attempts.Should().Be(1);
    }

    [Fact]
    public async Task DoesNotRetryDeepLAuthorizationException()
    {
        var pipeline = TranslationResiliencePipeline.Build();
        var attempts = 0;

        var act = async () => await pipeline.ExecuteAsync(async _ =>
        {
            attempts++;
            throw new AuthorizationException("bad key");
#pragma warning disable CS0162
            return await ValueTask.FromResult("never");
#pragma warning restore CS0162
        });

        await act.Should().ThrowAsync<AuthorizationException>();
        attempts.Should().Be(1);
    }

    [Fact]
    public async Task ExhaustsRetryBudget_ThenRethrows()
    {
        var pipeline = TranslationResiliencePipeline.Build();
        var attempts = 0;

        var act = async () => await pipeline.ExecuteAsync(async _ =>
        {
            attempts++;
            throw new HttpRequestException("always transient");
#pragma warning disable CS0162
            return await ValueTask.FromResult("never");
#pragma warning restore CS0162
        });

        await act.Should().ThrowAsync<HttpRequestException>();
        attempts.Should().Be(4); // initial attempt + 3 retries
    }
}