av-parser/tests/AvParser.Infrastructure.Tests/ProxyStateStoreTests.cs

using AvParser.Core.Proxies;
using AvParser.Infrastructure.Proxies;
using AvParser.Infrastructure.Storage;
using Microsoft.Extensions.Logging.Abstractions;

namespace AvParser.Infrastructure.Tests;

public sealed class ProxyStateStoreTests : IDisposable
{
    private readonly string _directory = Path.Combine(
        Path.GetTempPath(),
        "AvParserTests",
        Guid.NewGuid().ToString("N")
    );

    private ProxyStateStore Create() => new(new AppPaths(_directory), NullLogger<ProxyStateStore>.Instance);

    public void Dispose()
    {
        if (Directory.Exists(_directory))
        {
            Directory.Delete(_directory, recursive: true);
        }
    }

    private static ProxyEntry Entry(string address, ProxySourceKind kind = ProxySourceKind.Feed)
    {
        ProxyEndpoint.TryParse(address, out var endpoint).ShouldBeTrue();

        return new ProxyEntry(endpoint!, kind);
    }

    [Fact]
    public async Task An_absent_file_reads_as_nothing_remembered()
    {
        var store = Create();

        (await store.LoadAsync(TestContext.Current.CancellationToken)).ShouldBeEmpty();
    }

    [Fact]
    public async Task A_working_proxy_survives_a_round_trip()
    {
        var alive = Entry("http://1.2.3.4:8080");
        alive.RecordSuccess(DateTimeOffset.UtcNow, TimeSpan.FromMilliseconds(250));

        await Create().SaveAsync([alive], TestContext.Current.CancellationToken);
        var state = await Create().LoadAsync(TestContext.Current.CancellationToken);

        state.ShouldContainKey(alive.Endpoint.Key);
        state[alive.Endpoint.Key].Alive.ShouldBeTrue();
        state[alive.Endpoint.Key].LatencyMs.ShouldBe(250d);
    }

    [Fact]
    public async Task Proxies_that_never_answered_are_not_remembered()
    {
        // The feed republishes a few thousand dead addresses every few minutes; carrying them over
        // would bloat the file to save re-testing entries whose staleness tells us nothing.
        var untried = Entry("http://1.2.3.4:8080");
        var dead = Entry("http://5.6.7.8:3128");
        dead.RecordProbe(DateTimeOffset.UtcNow, alive: false, latency: null, error: "timeout");

        await Create().SaveAsync([untried, dead], TestContext.Current.CancellationToken);

        (await Create().LoadAsync(TestContext.Current.CancellationToken)).ShouldBeEmpty();
    }

    [Fact]
    public void Applying_remembered_state_restores_the_matching_entries_only()
    {
        var known = Entry("http://1.2.3.4:8080");
        var unknown = Entry("http://9.9.9.9:8080");
        var state = new Dictionary<string, ProxyStateRecord>(StringComparer.Ordinal)
        {
            [known.Endpoint.Key] = new(
                known.Endpoint.ToString(),
                Alive: true,
                LatencyMs: 120,
                SuccessCount: 7,
                FailureCount: 2
            ),
        };

        ProxyStateStore.Apply([known, unknown], state).ShouldBe(1);

        known.WasAliveOnLastRun.ShouldBeTrue();
        known.Latency.ShouldBe(TimeSpan.FromMilliseconds(120));
        known.SuccessCount.ShouldBe(7);
        unknown.WasAliveOnLastRun.ShouldBeFalse();
    }

    [Fact]
    public void A_remembered_proxy_is_not_reported_live_until_it_answers_again()
    {
        // Otherwise a launch a week later would open the parser gate on week-old evidence, and the
        // warm-up would skip the very proxies it was supposed to re-check.
        var entry = Entry("http://1.2.3.4:8080");
        var state = new Dictionary<string, ProxyStateRecord>(StringComparer.Ordinal)
        {
            [entry.Endpoint.Key] = new(entry.Endpoint.ToString(), Alive: true),
        };

        ProxyStateStore.Apply([entry], state);

        entry.Health.ShouldBe(ProxyHealthState.Unknown);
        entry.IsBelievedAlive.ShouldBeTrue();
    }

    [Fact]
    public async Task A_remembered_proxy_that_was_never_re_checked_is_still_remembered()
    {
        // The warm-up stops early, so most remembered entries end a session unprobed. Dropping
        // them on save would erode the remembered set to nothing over a few launches.
        var entry = Entry("http://1.2.3.4:8080");
        ProxyStateStore.Apply(
            [entry],
            new Dictionary<string, ProxyStateRecord>(StringComparer.Ordinal)
            {
                [entry.Endpoint.Key] = new(entry.Endpoint.ToString(), Alive: true),
            }
        );

        await Create().SaveAsync([entry], TestContext.Current.CancellationToken);

        (await Create().LoadAsync(TestContext.Current.CancellationToken)).ShouldContainKey(entry.Endpoint.Key);
    }

    [Fact]
    public async Task A_remembered_proxy_that_fails_its_re_check_is_forgotten()
    {
        var entry = Entry("http://1.2.3.4:8080");
        ProxyStateStore.Apply(
            [entry],
            new Dictionary<string, ProxyStateRecord>(StringComparer.Ordinal)
            {
                [entry.Endpoint.Key] = new(entry.Endpoint.ToString(), Alive: true),
            }
        );

        entry.RecordProbe(DateTimeOffset.UtcNow, alive: false, latency: null, error: "timeout");

        await Create().SaveAsync([entry], TestContext.Current.CancellationToken);

        (await Create().LoadAsync(TestContext.Current.CancellationToken)).ShouldBeEmpty();
    }

    [Fact]
    public void A_remembered_proxy_is_never_restored_into_a_quarantine()
    {
        // The window is wall-clock; a restart may be days later, so an expired sideline must not
        // be resurrected — the whole point of remembering is to start from the good ones.
        var entry = Entry("http://1.2.3.4:8080");
        entry.RecordFailure(DateTimeOffset.UtcNow, TimeSpan.FromMinutes(5), TimeSpan.FromHours(1), 1);
        entry.IsQuarantined(DateTimeOffset.UtcNow).ShouldBeTrue();

        var restored = new Dictionary<string, ProxyStateRecord>(StringComparer.Ordinal)
        {
            [entry.Endpoint.Key] = new(entry.Endpoint.ToString(), Alive: true),
        };

        ProxyStateStore.Apply([entry], restored);

        entry.IsQuarantined(DateTimeOffset.UtcNow).ShouldBeFalse();
    }
}