lmxopcua/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests/AtTimeEvaluatorTests.cs

using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using static ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests.Fixture;

namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Sql.Common.Tests;

/// <summary>Direct tests of the AtTime rules, with the literals of the SqlServer <c>AtTimeReadTests</c>.</summary>
public sealed class AtTimeEvaluatorTests
{
    private static readonly DateTime Now = At(3600);

    [Fact]
    public void AtTime_inside_an_outage_returns_the_bad_neighbours_code_with_no_value()
    {
        var t0 = new DateTime(2026, 10, 9, 8, 0, 0, DateTimeKind.Utc);
        var prev = new StoredSample(t0, HistorianValue.Empty, 0x80310000u);
        var next = new StoredSample(t0.AddSeconds(10), HistorianValue.FromDouble(5), 0);
        var r = AtTimeEvaluator.Evaluate(t0.AddSeconds(5), prev, next, t0, t0.AddHours(1));
        r.StatusCode.ShouldBe(0x80310000u);
        r.Value.ShouldBeNull();
    }

    [Fact]
    public void A_bad_valued_previous_neighbour_keeps_its_code_and_drops_its_value()
    {
        var r = AtTimeEvaluator.Evaluate(At(25), A[2], A[3], Now, Now);
        r.Value.ShouldBeNull();                 // NOT 35 and NOT 30
        r.StatusCode.ShouldBe(0x80000000u);
        r.SourceTimestampUtc.ShouldBe(At(25));
    }

    [Fact]
    public void Exact_hit_returns_the_stored_value_and_status_unchanged()
    {
        var r = AtTimeEvaluator.Evaluate(At(20), A[2], A[3], At(21), Now);
        r.Value.ShouldBe(30d);
        r.StatusCode.ShouldBe(0x80000000u);
        r.ServerTimestampUtc.ShouldBe(At(21));
    }

    [Fact]
    public void No_previous_sample_is_BadNoData_with_no_value()
    {
        var r = AtTimeEvaluator.Evaluate(At(0).AddTicks(-1), null, A[0], Now, Now);
        r.Value.ShouldBeNull();
        r.StatusCode.ShouldBe(0x809B0000u);
        r.SourceTimestampUtc.ShouldBe(At(0).AddTicks(-1));
    }

    [Fact]
    public void A_bad_next_neighbour_holds_the_previous_value_uncertain()
    {
        var r = AtTimeEvaluator.Evaluate(At(15), A[1], A[2], Now, Now);
        r.Value.ShouldBe(20d); // NOT 25
        r.StatusCode.ShouldBe(UncertainInterpolated);
    }

    [Fact]
    public void Between_two_good_doubles_is_linearly_interpolated_good()
    {
        AtTimeEvaluator.Evaluate(At(5), A[0], A[1], Now, Now).Value.ShouldBe(15d);
        AtTimeEvaluator.Evaluate(At(2.5), A[0], A[1], Now, Now).Value.ShouldBe(12.5d);
        var r = AtTimeEvaluator.Evaluate(At(32.5), A[3], A[4], Now, Now);
        r.Value.ShouldBe(42.5d);
        r.StatusCode.ShouldBe(GoodInterpolated);
        r.SourceTimestampUtc.ShouldBe(At(32.5));
    }

    [Fact]
    public void An_uncertain_neighbour_makes_the_interpolation_uncertain()
    {
        var r = AtTimeEvaluator.Evaluate(At(5), S(0, HistorianValue.FromDouble(10), Uncertain),
            S(10, HistorianValue.FromDouble(20), Good), Now, Now);
        r.Value.ShouldBe(15d);
        r.StatusCode.ShouldBe(UncertainInterpolated);
    }

    [Fact]
    public void Int64_is_interpolated_and_rounded_away_from_zero_keeping_its_type()
    {
        var p = S(0, HistorianValue.FromInt64(10), Good);
        var n = S(10, HistorianValue.FromInt64(15), Good);
        AtTimeEvaluator.Evaluate(At(5), p, n, Now, Now).Value.ShouldBe(13L); // 12.5 ⇒ 13
        AtTimeEvaluator.Evaluate(At(2), p, n, Now, Now).Value.ShouldBe(11L);
    }

    [Fact]
    public void After_the_last_sample_the_value_is_stepped_good_until_now_then_uncertain()
    {
        var now = At(42);
        var held = AtTimeEvaluator.Evaluate(At(41), A[4], null, now, now);
        held.Value.ShouldBe(50d);
        held.StatusCode.ShouldBe(GoodInterpolated);
        var future = AtTimeEvaluator.Evaluate(At(45), A[4], null, now, now);
        future.Value.ShouldBe(50d);
        future.StatusCode.ShouldBe(UncertainInterpolated);
    }

    [Fact]
    public void A_non_numeric_kind_is_stepped_with_the_previous_status_plus_interpolated()
    {
        var p = S(0, HistorianValue.FromString("a"), Uncertain);
        var n = S(10, HistorianValue.FromString("b"), Good);
        var r = AtTimeEvaluator.Evaluate(At(5), p, n, Now, Now);
        r.Value.ShouldBe("a");
        r.StatusCode.ShouldBe(Uncertain | 0x402u);
    }

    [Fact]
    public void An_uncertain_next_neighbour_makes_the_interpolation_uncertain()
    {
        var r = AtTimeEvaluator.Evaluate(At(5), S(0, HistorianValue.FromDouble(10), Good),
            S(10, HistorianValue.FromDouble(20), Uncertain), Now, Now);
        r.Value.ShouldBe(15d);
        r.StatusCode.ShouldBe(UncertainInterpolated);
    }
}