using Microsoft.Extensions.Logging.Abstractions;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests;

/// <summary>
///     Gitea #686: the gateway's <c>ReadRaw</c> streams ascending only and rejects <c>start &gt; end</c> with
///     <c>InvalidArgument</c>, which used to be recorded as a backend health failure. The source declares it cannot read
///     newest-first (so the server walks back with forward reads), and refuses a reverse window itself without sending
///     anything or counting a failure.
/// </summary>
public sealed class GatewayRawDirectionTests
{
    private static CancellationToken Ct => TestContext.Current.CancellationToken;

    [Fact]
    public void The_gateway_source_declares_it_cannot_read_raw_newest_first()
    {
        IHistorianDataSource ds = new GatewayHistorianDataSource(
            new FakeHistorianGatewayClient(), NullLogger<GatewayHistorianDataSource>.Instance);
        ds.SupportsReverseRaw.ShouldBeFalse();
    }

    [Fact]
    public async Task A_reverse_raw_window_is_refused_unsent_and_is_not_a_backend_failure()
    {
        var fake = new FakeHistorianGatewayClient();
        IHistorianDataSource ds = new GatewayHistorianDataSource(fake, NullLogger<GatewayHistorianDataSource>.Instance);
        var end = new DateTime(2026, 10, 12, 18, 7, 45, DateTimeKind.Utc);

        await Should.ThrowAsync<NotSupportedException>(() =>
            ds.ReadRawAsync("Gate681", end, new DateTime(0, DateTimeKind.Utc), 3, Ct));

        fake.ReadRawCallCount.ShouldBe(0);
        var health = ds.GetHealthSnapshot();
        health.TotalFailures.ShouldBe(0);
        health.ConsecutiveFailures.ShouldBe(0);

        // Positive control: a forward read of the same window is sent.
        await ds.ReadRawAsync("Gate681", new DateTime(2026, 10, 12, 18, 0, 0, DateTimeKind.Utc), end, 3, Ct);
        fake.ReadRawCallCount.ShouldBe(1);
    }
}