using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Conformance;

/// <summary>
///     Push-down aggregates over tag A (+0=10, +10=20, +20=Bad(30), +30=40, +40=50), 20 s intervals from the
///     sub-millisecond <see cref="ConformanceData.T0"/>, window [t0, t0+80s) ⇒ four buckets:
///     B0 [0,20) = {10, 20}; B1 [20,40) = {Bad 30, 40}; B2 [40,60) = {50}; B3 [60,80) = {} (empty).
///     Every expected value below is hand-computed.
/// </summary>
public abstract class ProcessedConformance : ConformanceBase
{
    private static readonly CancellationToken Ct = CancellationToken.None;
    private static readonly TimeSpan Twenty = TimeSpan.FromSeconds(20);

    // Calculated = InfoType DataValue 0x400 | Calculated 0x1, OR-ed onto the code.
    private const uint GoodCalc = 0x00000401u;
    private const uint UncertainCalc = 0x40A40401u;   // UncertainDataSubNormal | 0x401
    private const uint NoDataCalc = 0x809B0401u;      // BadNoData | 0x401
    private const uint InvalidInputsCalc = 0x80D60401u; // BadAggregateInvalidInputs | 0x401

    private async Task<HistoryReadResult> ReadA(HistoryAggregateType agg) =>
        await B.CreateDataSource().ReadProcessedAsync("A", At(0), At(80), Twenty, agg, Ct);

    [Fact]
    public void The_status_literals_carry_the_SDK_Calculated_aggregate_bits()
    {
        new Opc.Ua.StatusCode(GoodCalc).AggregateBits.ShouldBe(Opc.Ua.AggregateBits.Calculated);
        new Opc.Ua.StatusCode(UncertainCalc).AggregateBits.ShouldBe(Opc.Ua.AggregateBits.Calculated);
        new Opc.Ua.StatusCode(UncertainCalc).CodeBits.ShouldBe(Opc.Ua.StatusCodes.UncertainDataSubNormal);
        new Opc.Ua.StatusCode(NoDataCalc).CodeBits.ShouldBe(Opc.Ua.StatusCodes.BadNoData);
        new Opc.Ua.StatusCode(NoDataCalc).AggregateBits.ShouldBe(Opc.Ua.AggregateBits.Calculated);
        new Opc.Ua.StatusCode(InvalidInputsCalc).CodeBits.ShouldBe(Opc.Ua.StatusCodes.BadAggregateInvalidInputs);
    }

    [Theory]
    [InlineData(HistoryAggregateType.Average, 15d, 40d, 50d)]
    [InlineData(HistoryAggregateType.Minimum, 10d, 40d, 50d)]
    [InlineData(HistoryAggregateType.Maximum, 20d, 40d, 50d)]
    [InlineData(HistoryAggregateType.Start, 10d, 40d, 50d)]
    [InlineData(HistoryAggregateType.End, 20d, 40d, 50d)]
    [InlineData(HistoryAggregateType.Delta, 10d, 0d, 0d)]
    [InlineData(HistoryAggregateType.Range, 10d, 0d, 0d)]
    public async Task Numeric_aggregates_over_the_fixture(HistoryAggregateType agg, double b0, double b1, double b2)
    {
        await ConformanceData.SeedAAsync(B);
        var s = (await ReadA(agg)).Samples;

        s.Count.ShouldBe(4);
        s.Select(x => x.Value).ShouldBe([b0, b1, b2, null]);
        // B1 holds a Bad sample alongside a usable one ⇒ Uncertain; the empty B3 ⇒ BadNoData.
        s.Select(x => x.StatusCode).ShouldBe([GoodCalc, UncertainCalc, GoodCalc, NoDataCalc]);
        s.Select(x => x.SourceTimestampUtc).ShouldBe([B.Round(At(0)), B.Round(At(20)), B.Round(At(40)), B.Round(At(60))]); // bucket starts
    }

    [Fact]
    public async Task Count_counts_usable_samples_as_int()
    {
        await ConformanceData.SeedAAsync(B);
        var s = (await ReadA(HistoryAggregateType.Count)).Samples;
        s.Select(x => x.Value).ShouldBe([(object?)2, 1, 1, null]);
        s.Select(x => x.StatusCode).ShouldBe([GoodCalc, UncertainCalc, GoodCalc, NoDataCalc]);
    }

    [Theory]
    [InlineData(HistoryAggregateType.PercentGood, 100d, 50d, 100d)]
    [InlineData(HistoryAggregateType.PercentBad, 0d, 50d, 0d)]
    public async Task Percent_aggregates_count_every_sample(HistoryAggregateType agg, double b0, double b1, double b2)
    {
        await ConformanceData.SeedAAsync(B);
        var s = (await ReadA(agg)).Samples;
        s.Select(x => x.Value).ShouldBe([b0, b1, b2, null]);
        // A percentage is a statement about quality, so it is not itself degraded by the Bad input.
        s.Select(x => x.StatusCode).ShouldBe([GoodCalc, GoodCalc, GoodCalc, NoDataCalc]);
    }

    [Fact]
    public async Task Actual_time_aggregates_stamp_the_sample_time()
    {
        await ConformanceData.SeedAAsync(B);
        var min = (await ReadA(HistoryAggregateType.MinimumActualTime)).Samples;
        min.Select(x => x.Value).ShouldBe([10d, 40d, 50d, null]);
        min.Select(x => x.SourceTimestampUtc).ShouldBe([B.Round(At(0)), B.Round(At(30)), B.Round(At(40)), B.Round(At(60))]);
        min.Select(x => x.StatusCode).ShouldBe([GoodCalc, UncertainCalc, GoodCalc, NoDataCalc]);
        var max = (await ReadA(HistoryAggregateType.MaximumActualTime)).Samples;
        max.Select(x => x.Value).ShouldBe([20d, 40d, 50d, null]);
        max.Select(x => x.SourceTimestampUtc).ShouldBe([B.Round(At(10)), B.Round(At(30)), B.Round(At(40)), B.Round(At(60))]);
    }

    [Fact]
    public async Task Actual_time_ties_resolve_to_the_earliest_sample()
    {
        await B.SeedAsync("T",
            (At(0), HistorianValue.FromDouble(5), Good),
            (At(2), HistorianValue.FromDouble(3), Good),
            (At(4), HistorianValue.FromDouble(3), Good),
            (At(6), HistorianValue.FromDouble(7), Good),
            (At(8), HistorianValue.FromDouble(7), Good));
        var src = B.CreateDataSource();
        var min = (await src.ReadProcessedAsync("T", At(0), At(10), TimeSpan.Zero, HistoryAggregateType.MinimumActualTime, Ct)).Samples.Single();
        min.Value.ShouldBe(3d);
        min.SourceTimestampUtc.ShouldBe(B.Round(At(2)));
        var max = (await src.ReadProcessedAsync("T", At(0), At(10), TimeSpan.Zero, HistoryAggregateType.MaximumActualTime, Ct)).Samples.Single();
        max.Value.ShouldBe(7d);
        max.SourceTimestampUtc.ShouldBe(B.Round(At(6)));
    }

    [Fact]
    public async Task Bucket_edges_are_start_inclusive_end_exclusive_to_the_tick()
    {
        // T0 is not millisecond-aligned: a DATEDIFF(millisecond) bucket formula would push the sample one tick
        // before the +20 s edge into bucket 1 (it counts millisecond boundaries crossed, not elapsed time).
        var edge = At(20);
        await B.SeedAsync("E",
            (At(0).AddTicks(-B.ResolutionTicks), HistorianValue.FromDouble(1000), Good), // before start: excluded
            (At(0), HistorianValue.FromDouble(1), Good),                  // == start: B0
            (edge.AddTicks(-B.ResolutionTicks), HistorianValue.FromDouble(2), Good),      // last tick of B0
            (edge, HistorianValue.FromDouble(4), Good),                   // first tick of B1
            (At(40).AddTicks(-B.ResolutionTicks), HistorianValue.FromDouble(8), Good),    // last tick of B1
            (At(40), HistorianValue.FromDouble(2000), Good));             // == end: excluded
        var s = (await B.CreateDataSource().ReadProcessedAsync("E", At(0), At(40), Twenty, HistoryAggregateType.Average, Ct)).Samples;
        s.Select(x => x.Value).ShouldBe([1.5d, 6d]);
        s.ShouldAllBe(x => x.StatusCode == GoodCalc);
    }

    [Fact]
    public async Task A_partial_last_interval_is_truncated_at_end()
    {
        await ConformanceData.SeedAAsync(B);
        var s = (await B.CreateDataSource().ReadProcessedAsync("A", At(0), At(50), Twenty, HistoryAggregateType.Average, Ct)).Samples;
        s.Select(x => x.SourceTimestampUtc).ShouldBe([B.Round(At(0)), B.Round(At(20)), B.Round(At(40))]);
        s.Select(x => x.Value).ShouldBe([15d, 40d, 50d]);
    }

    [Fact]
    public async Task A_non_positive_interval_is_one_interval_over_the_window()
    {
        await ConformanceData.SeedAAsync(B);
        var src = B.CreateDataSource();
        var avg = (await src.ReadProcessedAsync("A", At(0), At(50), TimeSpan.Zero, HistoryAggregateType.Average, Ct)).Samples.Single();
        avg.Value.ShouldBe(30d); // usable {10, 20, 40, 50}
        avg.StatusCode.ShouldBe(UncertainCalc);
        avg.SourceTimestampUtc.ShouldBe(B.Round(At(0)));
        (await src.ReadProcessedAsync("A", At(0), At(50), TimeSpan.FromSeconds(-1), HistoryAggregateType.Count, Ct))
            .Samples.Single().Value.ShouldBe(4);
    }

    [Fact]
    public async Task A_whole_range_single_interval_from_1601_to_9999_does_not_overflow()
    {
        // 1601-01-01 is the OPC UA minimum DateTime. A nanosecond DATEDIFF_BIG overflows past ≈292 years (SQL 535),
        // and a ns-scaled interval would wrap a long; both must be gone.
        await ConformanceData.SeedAAsync(B);
        var start = new DateTime(1601, 1, 1, 0, 0, 0, DateTimeKind.Utc);
        var end = new DateTime(9999, 12, 31, 0, 0, 0, DateTimeKind.Utc);
        var src = B.CreateDataSource();
        var avg = (await src.ReadProcessedAsync("A", start, end, TimeSpan.Zero, HistoryAggregateType.Average, Ct)).Samples.Single();
        avg.Value.ShouldBe(30d); // usable {10, 20, 40, 50}
        avg.StatusCode.ShouldBe(UncertainCalc);
        avg.SourceTimestampUtc.ShouldBe(start);
        (await src.ReadProcessedAsync("A", start, end, TimeSpan.Zero, HistoryAggregateType.Count, Ct))
            .Samples.Single().Value.ShouldBe(4);
        // Also a whole-DateTime-range window (0001 → 9999-12-31T23:59:59.9999999).
        (await src.ReadProcessedAsync("A", DateTime.MinValue, DateTime.MaxValue, TimeSpan.Zero, HistoryAggregateType.Count, Ct))
            .Samples.Single().Value.ShouldBe(4);
        // An interval wider than the window (here TimeSpan.MaxValue) is the same single interval, no overflow.
        (await src.ReadProcessedAsync("A", start, end, TimeSpan.MaxValue, HistoryAggregateType.Count, Ct))
            .Samples.Single().Value.ShouldBe(4);
        // The time-weighted path over the whole range: ≈ the extrapolated 50 that dominates eight millennia.
        var tw = (await src.ReadProcessedAsync("A", start, end, TimeSpan.Zero, HistoryAggregateType.TimeAverage2, Ct)).Samples.Single();
        ((double)tw.Value!).ShouldBe(50d, 1e-6);
        tw.StatusCode.ShouldBe(UncertainCalc);
        src.GetHealthSnapshot().TotalFailures.ShouldBe(0);
    }

    [Fact]
    public async Task A_weekly_interval_over_four_centuries_lands_samples_in_the_right_week()
    {
        // Hand-computed (calendar arithmetic, independent of SQL): 1601-01-01 → 2027-01-01 is 155 593 days =
        // 22 227.57 weeks ⇒ 22 228 intervals (under the 100k cap). 2026-10-09 08:00 is 155 509 days in ⇒ week
        // index 22 215, which starts Monday 2026-10-05 00:00; every fixture sample (t0 … t0+40 s) is in it.
        await ConformanceData.SeedAAsync(B);
        var start = new DateTime(1601, 1, 1, 0, 0, 0, DateTimeKind.Utc);
        var end = new DateTime(2027, 1, 1, 0, 0, 0, DateTimeKind.Utc);
        var s = (await B.CreateDataSource().ReadProcessedAsync("A", start, end, TimeSpan.FromDays(7), HistoryAggregateType.Average, Ct)).Samples;

        s.Count.ShouldBe(22_228);
        var hit = s[22_215];
        hit.SourceTimestampUtc.ShouldBe(new DateTime(2026, 10, 5, 0, 0, 0, DateTimeKind.Utc));
        hit.Value.ShouldBe(30d);
        hit.StatusCode.ShouldBe(UncertainCalc);
        s.Where((_, i) => i != 22_215).ShouldAllBe(x => x.StatusCode == NoDataCalc);
        s[^1].SourceTimestampUtc.ShouldBe(new DateTime(2026, 12, 28, 0, 0, 0, DateTimeKind.Utc)); // partial last week
    }

    [Fact]
    public async Task A_reverse_window_is_computed_forward_and_returned_descending()
    {
        await ConformanceData.SeedAAsync(B);
        var s = (await B.CreateDataSource().ReadProcessedAsync("A", At(80), At(0), Twenty, HistoryAggregateType.Average, Ct)).Samples;
        s.Select(x => x.SourceTimestampUtc).ShouldBe([B.Round(At(60)), B.Round(At(40)), B.Round(At(20)), B.Round(At(0))]);
        s.Select(x => x.Value).ShouldBe([null, 50d, 40d, 15d]);
    }

    [Fact]
    public async Task Equal_start_and_end_yields_no_intervals()
    {
        await ConformanceData.SeedAAsync(B);
        (await B.CreateDataSource().ReadProcessedAsync("A", At(10), At(10), Twenty, HistoryAggregateType.Average, Ct))
            .Samples.ShouldBeEmpty();
    }

    [Fact]
    public async Task Outage_markers_are_bad_samples_in_aggregates()
    {
        await B.SeedAsync("M",
            (At(0), HistorianValue.FromDouble(10), Good),
            (At(5), HistorianValue.Empty, BadNoCommunication),
            (At(10), HistorianValue.FromDouble(30), Good));
        var src = B.CreateDataSource();
        async Task<DataValueSnapshot> One(HistoryAggregateType a) =>
            (await src.ReadProcessedAsync("M", At(0), At(20), Twenty, a, Ct)).Samples.Single();

        var avg = await One(HistoryAggregateType.Average);
        avg.Value.ShouldBe(20d);
        avg.StatusCode.ShouldBe(UncertainCalc);
        (await One(HistoryAggregateType.Count)).Value.ShouldBe(2);
        (await One(HistoryAggregateType.Start)).Value.ShouldBe(10d);
        ((double)(await One(HistoryAggregateType.PercentBad)).Value!).ShouldBe(33.333333333333336, 1e-9); // 100 × 1/3
    }

    [Fact]
    public async Task An_interval_of_only_bad_samples_is_BadNoData_except_the_percentages()
    {
        await B.SeedAsync("Z",
            (At(1), HistorianValue.Empty, BadNoCommunication),
            (At(2), HistorianValue.FromDouble(5), Bad));
        var src = B.CreateDataSource();
        async Task<DataValueSnapshot> One(HistoryAggregateType a) =>
            (await src.ReadProcessedAsync("Z", At(0), At(20), Twenty, a, Ct)).Samples.Single();

        (await One(HistoryAggregateType.Average)).StatusCode.ShouldBe(NoDataCalc);
        (await One(HistoryAggregateType.Count)).StatusCode.ShouldBe(NoDataCalc);
        var pb = await One(HistoryAggregateType.PercentBad);
        pb.Value.ShouldBe(100d);
        pb.StatusCode.ShouldBe(GoodCalc);
    }

    [Fact]
    public async Task Uncertain_samples_are_used_but_make_the_interval_uncertain()
    {
        await B.SeedAsync("U",
            (At(1), HistorianValue.FromDouble(4), Uncertain),
            (At(2), HistorianValue.FromDouble(6), Good));
        var s = (await B.CreateDataSource().ReadProcessedAsync("U", At(0), At(20), Twenty, HistoryAggregateType.Average, Ct)).Samples.Single();
        s.Value.ShouldBe(5d);
        s.StatusCode.ShouldBe(UncertainCalc);
    }

    [Fact]
    public async Task String_tags_serve_count_start_end_and_refuse_numeric_aggregates()
    {
        await B.SeedAsync("S",
            (At(0), HistorianValue.FromString("a"), Good),
            (At(10), HistorianValue.FromString("b"), Good));
        var src = B.CreateDataSource();
        async Task<DataValueSnapshot> One(HistoryAggregateType a) =>
            (await src.ReadProcessedAsync("S", At(0), At(20), Twenty, a, Ct)).Samples.Single();

        (await One(HistoryAggregateType.Count)).Value.ShouldBe(2);
        (await One(HistoryAggregateType.Start)).Value.ShouldBe("a");
        (await One(HistoryAggregateType.End)).Value.ShouldBe("b");
        (await One(HistoryAggregateType.PercentGood)).Value.ShouldBe(100d);
        foreach (var a in new[]
                 {
                     HistoryAggregateType.Average, HistoryAggregateType.Minimum, HistoryAggregateType.Maximum,
                     HistoryAggregateType.Total, HistoryAggregateType.Delta, HistoryAggregateType.Range,
                     HistoryAggregateType.MinimumActualTime, HistoryAggregateType.MaximumActualTime,
                 })
        {
            var r = await One(a);
            r.StatusCode.ShouldBe(InvalidInputsCalc, a.ToString());
            r.Value.ShouldBeNull();
        }
    }

    [Fact]
    public async Task DateTime_tags_refuse_numeric_aggregates()
    {
        await B.SeedAsync("D", (At(0), HistorianValue.FromDateTime(At(-100)), Good));
        (await B.CreateDataSource().ReadProcessedAsync("D", At(0), At(20), Twenty, HistoryAggregateType.Average, Ct))
            .Samples.Single().StatusCode.ShouldBe(InvalidInputsCalc);
    }

    [Fact]
    public async Task Boolean_tags_aggregate_as_zero_or_one()
    {
        await B.SeedAsync("B",
            (At(0), HistorianValue.FromBoolean(true), Good),
            (At(5), HistorianValue.FromBoolean(false), Good),
            (At(10), HistorianValue.FromBoolean(true), Good),
            (At(15), HistorianValue.FromBoolean(true), Good));
        var src = B.CreateDataSource();
        async Task<DataValueSnapshot> One(HistoryAggregateType a) =>
            (await src.ReadProcessedAsync("B", At(0), At(20), Twenty, a, Ct)).Samples.Single();
        (await One(HistoryAggregateType.Average)).Value.ShouldBe(0.75d);
        // Total is time-weighted (#671): stepped 1 over [0,5), 0 over [5,10), 1 over [10,20) ⇒ 15 value·s.
        (await One(HistoryAggregateType.Total)).Value.ShouldBe(15d);
        (await One(HistoryAggregateType.Start)).Value.ShouldBe(true);
        (await One(HistoryAggregateType.Count)).Value.ShouldBe(4);
    }

    [Fact]
    public async Task Unknown_tag_yields_every_interval_as_BadNoData()
    {
        var s = (await B.CreateDataSource().ReadProcessedAsync("nope", At(0), At(60), Twenty, HistoryAggregateType.Average, Ct)).Samples;
        s.Count.ShouldBe(3);
        s.ShouldAllBe(x => x.StatusCode == NoDataCalc && x.Value == null);
    }

    [Theory]
    [InlineData(HistoryAggregateType.StartBound)]
    [InlineData(HistoryAggregateType.EndBound)]
    [InlineData(HistoryAggregateType.DeltaBounds)]
    [InlineData(HistoryAggregateType.DurationGood)]
    [InlineData(HistoryAggregateType.DurationBad)]
    [InlineData(HistoryAggregateType.WorstQuality)]
    [InlineData(HistoryAggregateType.NumberOfTransitions)]
    [InlineData(HistoryAggregateType.AnnotationCount)]
    [InlineData(HistoryAggregateType.StandardDeviationPopulation)]
    [InlineData(HistoryAggregateType.VariancePopulation)]
    public async Task Unsupported_aggregates_throw_not_supported_and_are_not_health_failures(HistoryAggregateType agg)
    {
        var src = B.CreateDataSource();
        var ex = await Should.ThrowAsync<HistoryAggregateNotSupportedException>(
            () => src.ReadProcessedAsync("A", At(0), At(20), Twenty, agg, Ct));
        ex.Aggregate.ShouldBe(agg);
        src.GetHealthSnapshot().TotalQueries.ShouldBe(0);
    }

    // ------------------------------------------------------------------------------------------ Time-weighted (#671)

    private const uint GoodRaw = 0x00000000u;
    private const uint GoodInterp = 0x00000402u;        // Good | InfoType 0x400 | Interpolated 0x2
    private const uint UncertainInterp = 0x40A40402u;   // UncertainDataSubNormal | 0x402
    private const uint NoData = 0x809B0000u;
    private const uint BadCalc = 0x80000401u;           // generic Bad | Calculated (an all-outage interval)

    /// <summary>
    ///     Sparse tag W: −30 = 0 G (bound before the window), +20 = 40 G, +30 = outage marker, +50 = 20 G, +100 = 20 G
    ///     (bound after the window). Window [t0, t0+80s). Simple-bounding signal: [−30,20) 0→40 sloped Good (24 at +0,
    ///     32 at +10); [20,30) 40 held into the outage, Uncertain; [30,50) Bad; [50,100) 20 Good. Interpolated bounding:
    ///     the same, but [20,50) is sloped 40→20 straight across the outage (100/3 at +30, 80/3 at +40).
    /// </summary>
    private Task SeedWAsync() => B.SeedAsync("W",
        (At(-30), HistorianValue.FromDouble(0), Good),
        (At(20), HistorianValue.FromDouble(40), Good),
        (At(30), HistorianValue.Empty, BadNoCommunication),
        (At(50), HistorianValue.FromDouble(20), Good),
        (At(100), HistorianValue.FromDouble(20), Good));

    private async Task<IReadOnlyList<DataValueSnapshot>> ReadW(HistoryAggregateType agg, double intervalS) =>
        (await B.CreateDataSource().ReadProcessedAsync("W", At(0), At(80), TimeSpan.FromSeconds(intervalS), agg, Ct)).Samples;

    private static void Values(IReadOnlyList<DataValueSnapshot> s, params double?[] expected)
    {
        s.Count.ShouldBe(expected.Length);
        for (var i = 0; i < expected.Length; i++)
        {
            if (expected[i] is { } e) ((double)s[i].Value!).ShouldBe(e, 1e-9, $"bucket {i}");
            else s[i].Value.ShouldBeNull($"bucket {i}");
        }
    }

    [Theory]
    // 40 s intervals (wider than the sample gaps). B0 [0,40): raw [0,20) 24→40 = 640 Good + [20,30) 40 = 400 Uncertain,
    // [30,40) Bad; bridged 640 + [20,40) 40→80/3 = 2000/3. B1 [40,80): raw [50,80) 20 = 600 Good, [40,50) Bad; bridged
    // [40,50) 80/3→20 = 700/3 + 600.
    [InlineData(HistoryAggregateType.TimeAverage, 98d / 3d, 125d / 6d)]       // (3920/3)/40, (2500/3)/40
    [InlineData(HistoryAggregateType.Total, 3920d / 3d, 2500d / 3d)]          // TimeAverage × 40 s
    [InlineData(HistoryAggregateType.TimeAverage2, 104d / 3d, 20d)]           // 1040/30 s, 600/30 s
    [InlineData(HistoryAggregateType.Total2, 1040d, 600d)]
    public async Task Time_weighted_aggregates_over_a_sparse_tag_with_wide_intervals(HistoryAggregateType agg, double b0, double b1)
    {
        await SeedWAsync();
        var s = await ReadW(agg, 40);
        Values(s, b0, b1);
        // Neither interval is Good throughout (an outage in each) ⇒ Uncertain.
        s.Select(x => x.StatusCode).ShouldBe([UncertainCalc, UncertainCalc]);
        s.Select(x => x.SourceTimestampUtc).ShouldBe([B.Round(At(0)), B.Round(At(40))]);
    }

    [Fact]
    public async Task Interpolative_over_a_sparse_tag_with_wide_intervals()
    {
        await SeedWAsync();
        var s = await ReadW(HistoryAggregateType.Interpolative, 40);
        // +0: from the bound before the window, 0 + 40·(30/50) = 24, Good. +40: inside the outage, bridged 80/3, Uncertain.
        Values(s, 24, 80d / 3d);
        s.Select(x => x.StatusCode).ShouldBe([GoodInterp, UncertainInterp]);
    }

    [Fact]
    public async Task TimeAverage2_over_a_sparse_tag_with_narrow_intervals()
    {
        await SeedWAsync();
        // 10 s intervals (narrower than the gaps): [0,10) 24→32 = 28; [10,20) 32→40 = 36; [20,30) 40 held up to the
        // outage (Uncertain time, which counts as Good: TreatUncertainAsBad = false); [30,40) and [40,50) inside the outage
        // ⇒ generic Bad (data, but none non-Bad); [50,60) … [70,80) the flat 20 up to the bound after, Good.
        var s = await ReadW(HistoryAggregateType.TimeAverage2, 10);
        Values(s, 28, 36, 40, null, null, 20, 20, 20);
        s.Select(x => x.StatusCode).ShouldBe(
            [GoodCalc, GoodCalc, GoodCalc, BadCalc, BadCalc, GoodCalc, GoodCalc, GoodCalc]);
        // Total2 of the first interval: 28 × 10 s.
        ((double)(await ReadW(HistoryAggregateType.Total2, 10))[0].Value!).ShouldBe(280d, 1e-9);
    }

    [Fact]
    public async Task Interpolative_over_a_sparse_tag_with_narrow_intervals()
    {
        await SeedWAsync();
        var s = await ReadW(HistoryAggregateType.Interpolative, 10);
        // +0 24, +10 32 (sloped from the bound); +20 exact 40 (raw Good); +30 ON the outage marker ⇒ bridged 100/3;
        // +40 bridged 80/3; +50 exact 20; +60, +70 on the Good 20→20 segment to the bound after.
        Values(s, 24, 32, 40, 100d / 3d, 80d / 3d, 20, 20, 20);
        s.Select(x => x.StatusCode).ShouldBe(
            [GoodInterp, GoodInterp, GoodRaw, UncertainInterp, UncertainInterp, GoodRaw, GoodInterp, GoodInterp]);
    }

    [Fact]
    public async Task A_reverse_Interpolative_read_is_anchored_at_its_later_time()
    {
        await SeedWAsync();
        // At(80) → At(0), 40 s: points At(80) (on the Good 20→20 segment to the bound at +100 ⇒ 20) and At(40) (inside
        // the outage ⇒ bridged 80/3, Uncertain), latest first. A forward read would answer At(0) and At(40) instead.
        var s = (await B.CreateDataSource().ReadProcessedAsync("W", At(80), At(0), TimeSpan.FromSeconds(40),
            HistoryAggregateType.Interpolative, Ct)).Samples;
        s.Select(x => x.SourceTimestampUtc).ShouldBe([B.Round(At(80)), B.Round(At(40))]);
        Values(s, 20, 80d / 3d);
        s.Select(x => x.StatusCode).ShouldBe([GoodInterp, UncertainInterp]);
    }

    [Fact]
    public async Task The_time_weighted_raw_row_cap_fails_the_read_past_the_cap_only()
    {
        // Tag A holds five samples in [0,80); W holds three in [0,80) plus two bound rows outside it.
        await ConformanceData.SeedAAsync(B);
        await SeedWAsync();
        var atCap = B.CreateDataSource(5);
        (await atCap.ReadProcessedAsync("A", At(0), At(80), Twenty, HistoryAggregateType.Total, Ct)).Samples.Count.ShouldBe(4);

        var under = B.CreateDataSource(4);
        var ex = await Should.ThrowAsync<HistoryReadLimitExceededException>(
            () => under.ReadProcessedAsync("A", At(0), At(80), Twenty, HistoryAggregateType.Total, Ct));
        ex.Limit.ShouldBe(4);
        // Pushed-down (per-sample) aggregates are not capped; the bound rows outside the window do not count.
        (await under.ReadProcessedAsync("A", At(0), At(80), Twenty, HistoryAggregateType.Average, Ct)).Samples.Count.ShouldBe(4);
        (await B.CreateDataSource(3).ReadProcessedAsync("W", At(0), At(80), Twenty, HistoryAggregateType.TimeAverage, Ct))
            .Samples.Count.ShouldBe(4);
        // A client-request limit, not a backend fault.
        under.GetHealthSnapshot().TotalFailures.ShouldBe(0);
        // Non-positive = unbounded.
        (await B.CreateDataSource(0).ReadProcessedAsync("A", At(0), At(80), Twenty, HistoryAggregateType.Total, Ct))
            .Samples.Count.ShouldBe(4);
    }

    [Fact]
    public async Task Outages_straddling_both_window_edges_use_the_four_bound_seeks()
    {
        // −10 = 0 G, −5 outage, +10 = 20 G, +20 outage, +30 = 40 G; window [0,20). The four seeks return −10 (latest
        // usable before), −5 (latest before), +20 (first at/after end) and +30 (first usable at/after end).
        await B.SeedAsync("O",
            (At(-10), HistorianValue.FromDouble(0), Good),
            (At(-5), HistorianValue.Empty, BadNoCommunication),
            (At(10), HistorianValue.FromDouble(20), Good),
            (At(20), HistorianValue.Empty, BadNoCommunication),
            (At(30), HistorianValue.FromDouble(40), Good));
        var src = B.CreateDataSource();
        async Task<IReadOnlyList<DataValueSnapshot>> Read(HistoryAggregateType a, double intervalS) =>
            (await src.ReadProcessedAsync("O", At(0), At(20), TimeSpan.FromSeconds(intervalS), a, Ct)).Samples;

        // Bridged: −10..10 0→20 ⇒ [0,10) mean 15 (150); 10..30 20→40 ⇒ [10,20) mean 25 (250). 400 / 20 = 20.
        // (Without the usable-before seek: 250/10 = 25; without the usable-after seek: [10,20) held 20 ⇒ 17.5.)
        var ta = (await Read(HistoryAggregateType.TimeAverage, 0)).Single();
        ((double)ta.Value!).ShouldBe(20d, 1e-9);
        ta.StatusCode.ShouldBe(UncertainCalc);
        // Simple bounding: [0,10) inside the outage from −5; [10,20) 20 held into the outage at +20 ⇒ 200 / 10 s = 20.
        // (Without the any-before seek: (150+200)/20 = 17.5; without the any-after seek: [10,20) 20→30 ⇒ 25.)
        var ta2 = (await Read(HistoryAggregateType.TimeAverage2, 0)).Single();
        ((double)ta2.Value!).ShouldBe(20d, 1e-9);
        ta2.StatusCode.ShouldBe(UncertainCalc);
        // +0 inside the outage ⇒ bridged 10, Uncertain; +10 exact 20, raw Good.
        var i = await Read(HistoryAggregateType.Interpolative, 10);
        Values(i, 10, 20);
        i.Select(x => x.StatusCode).ShouldBe([UncertainInterp, GoodRaw]);
    }

    [Fact]
    public async Task Time_weighted_aggregates_on_an_unknown_tag_are_BadNoData()
    {
        var src = B.CreateDataSource();
        (await src.ReadProcessedAsync("nope", At(0), At(40), Twenty, HistoryAggregateType.TimeAverage, Ct))
            .Samples.ShouldAllBe(x => x.StatusCode == NoDataCalc);
        (await src.ReadProcessedAsync("nope", At(0), At(40), Twenty, HistoryAggregateType.Interpolative, Ct))
            .Samples.ShouldAllBe(x => x.StatusCode == NoData);
        src.GetHealthSnapshot().TotalFailures.ShouldBe(0);
    }

    [Fact]
    public async Task The_bucket_count_is_capped_at_100000()
    {
        var src = B.CreateDataSource();
        var oneTick = TimeSpan.FromTicks(B.ResolutionTicks);
        (await src.ReadProcessedAsync("nope", At(0), At(0).AddTicks(100_000 * B.ResolutionTicks), oneTick, HistoryAggregateType.Count, Ct))
            .Samples.Count.ShouldBe(100_000);
        await Should.ThrowAsync<ArgumentOutOfRangeException>(
            () => src.ReadProcessedAsync("nope", At(0), At(0).AddTicks(100_001 * B.ResolutionTicks), oneTick, HistoryAggregateType.Count, Ct));
        var h = src.GetHealthSnapshot();
        h.TotalFailures.ShouldBe(0); // a client-request error, not a backend fault
    }
}