lmxopcua/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Tests/GatewayAtTimeTests.cs

using Google.Protobuf.WellKnownTypes;
using Microsoft.Extensions.Logging.Abstractions;
using Shouldly;
using Xunit;
using ZB.MOM.WW.HistorianGateway.Contracts.Grpc;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

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

/// <summary>
///     Gitea #693: Gateway HistoryRead AtTime is served from RAW reads and evaluated with the SQL backends' shared
///     <c>AtTimeEvaluator</c> (Part 11 §6.5.4) — never AVEVA's own interpolated answer, which the live gate caught returning
///     the previous value as Good at a stored NULL's own time, null + Bad at a Good sample right after a NULL, a drifted value
///     at an exact stored sample, and no Interpolated bit. The fake is AVEVA-shaped (the real wire shape): ReadRaw over
///     <c>[start, end]</c> ascending, capped, led by the synthetic boundary row at the query start (the value in effect there,
///     <c>Quality = 133</c>, or a NULL row), NULL rows as <c>NumericValue = 0</c> + <c>q=1 opc=0</c>, millisecond timestamps;
///     and it REJECTS what the real gateway rejects (<c>max_values &lt;= 0</c>, <c>end &lt; start</c>).
/// </summary>
public sealed class GatewayAtTimeTests
{
    private static CancellationToken Ct => TestContext.Current.CancellationToken;

    private const uint Good = 0u;
    private const uint Bad = 0x80000000u;
    private const uint BadNoData = 0x809B0000u;
    private const uint GoodInterpolated = 0x00000402u;
    private const uint UncertainInterpolated = 0x40A40402u; // UncertainDataSubNormal | InfoType DataValue | Interpolated

    /// <summary>The live gate's tag <c>HistGW.LiveTest.Gate685</c>: 19:00:03 is a stored NULL.</summary>
    private static readonly DateTime T0 = new(2026, 10, 12, 19, 0, 0, DateTimeKind.Utc);

    private static readonly DateTime Now = T0.AddHours(1);

    private static DateTime At(double seconds) => T0.AddTicks((long)(seconds * TimeSpan.TicksPerSecond));

    private static List<(DateTime T, double V, bool Null)> Gate685() =>
        [(At(0), 100, false), (At(2), 107, false), (At(3), 0, true), (At(5), 108, false)];

    /// <summary>An AVEVA-shaped store over sorted rows, counting reads and rejecting what the real gateway rejects.</summary>
    private sealed class AvevaStore
    {
        private readonly (DateTime T, double V, bool Null)[] _rows;

        public AvevaStore(IEnumerable<(DateTime T, double V, bool Null)> rows) => _rows = rows.OrderBy(r => r.T).ToArray();

        /// <summary>Also emit a row at the exact query END carrying the value in effect there (unverified AVEVA behaviour).</summary>
        public bool TerminalRow { get; init; }

        /// <summary>Total rows streamed (cost).</summary>
        public long RowsStreamed;

        public FakeHistorianGatewayClient Client(int? ceiling = null) => new()
        {
            RawSource = Serve,
            MaxValuesCeiling = ceiling,
        };

        private static HistorianSample Row(DateTime t, double v, bool isNull, uint quality = 0) => new()
        {
            Tag = "T",
            Timestamp = Timestamp.FromDateTime(t),
            NumericValue = isNull ? 0 : v,
            OpcQuality = isNull ? 0u : 192u,
            Quality = isNull ? 1u : quality,
        };

        private int FirstAtOrAfter(DateTime t)
        {
            int lo = 0, hi = _rows.Length;
            while (lo < hi)
            {
                var mid = (lo + hi) / 2;
                if (_rows[mid].T < t) lo = mid + 1; else hi = mid;
            }
            return lo;
        }

        private HistorianSample InEffect(DateTime t)
        {
            var i = FirstAtOrAfter(t) - 1;
            if (i < 0) return new HistorianSample { Tag = "T", Timestamp = Timestamp.FromDateTime(t), NumericValue = 0, OpcQuality = 0, Quality = 1 };
            var p = _rows[i];
            return Row(t, p.V, p.Null, p.Null ? 1u : 133u);
        }

        private IEnumerable<HistorianSample> Serve(DateTime start, DateTime end, int max)
        {
            if (max <= 0)
                throw new Grpc.Core.RpcException(new Grpc.Core.Status(Grpc.Core.StatusCode.InvalidArgument, "max_values must be greater than zero."));
            if (end < start)
                throw new Grpc.Core.RpcException(new Grpc.Core.Status(Grpc.Core.StatusCode.InvalidArgument,
                    "start_time must be less than or equal to end_time."));
            if (end > Now.AddDays(2))
                throw new Grpc.Core.RpcException(new Grpc.Core.Status(Grpc.Core.StatusCode.InvalidArgument,
                    "end_time is outside the historian's time range"));
            if (start.Ticks % TimeSpan.TicksPerMillisecond != 0 || end.Ticks % TimeSpan.TicksPerMillisecond != 0)
                throw new InvalidOperationException("AVEVA truncates request times to the millisecond; send millisecond bounds.");

            var rows = new List<HistorianSample>();
            var i = FirstAtOrAfter(start);
            if (i >= _rows.Length || _rows[i].T != start) rows.Add(InEffect(start));
            for (; i < _rows.Length && _rows[i].T <= end && rows.Count < max; i++)
                rows.Add(Row(_rows[i].T, _rows[i].V, _rows[i].Null));
            if (TerminalRow && rows.Count < max && (i >= _rows.Length || _rows[i].T > end) && _rows.All(r => r.T != end))
                rows.Add(InEffect(end));
            var served = rows.Take(max).ToList();
            RowsStreamed += served.Count;
            return served;
        }
    }

    private static GatewayHistorianDataSource Source(FakeHistorianGatewayClient fake) =>
        new(fake, NullLogger<GatewayHistorianDataSource>.Instance, timeProvider: new FixedTime(Now));

    private sealed class FixedTime(DateTime now) : TimeProvider
    {
        public override DateTimeOffset GetUtcNow() => new(now);
    }

    private static async Task<IReadOnlyList<DataValueSnapshot>> AtTime(FakeHistorianGatewayClient fake, params DateTime[] times)
    {
        var r = await Source(fake).ReadAtTimeAsync("T", times, Ct);
        r.Samples.Count.ShouldBe(times.Length);
        for (var i = 0; i < times.Length; i++) r.Samples[i].SourceTimestampUtc.ShouldBe(times[i]);
        var refused = fake.MaxValuesCeiling is { } c ? fake.RawCalls.Count(x => x.MaxValues > c) : 0;
        fake.RawStreamsCompleted.ShouldBe(fake.ReadRawCallCount - refused); // never abandons a gateway stream
        fake.ReadAtTimeCallCount.ShouldBe(0);                       // never AVEVA's own interpolation
        return r.Samples;
    }

    // ---- the four live findings ------------------------------------------------------------------------------------

    [Fact] // live: 19:00:03 (a stored NULL) ⇒ 107 Good
    public async Task At_a_stored_NULLs_own_time_is_null_and_Bad()
    {
        var s = (await AtTime(new AvevaStore(Gate685()).Client(), At(3))).Single();
        s.Value.ShouldBeNull();
        s.StatusCode.ShouldBe(Bad);
    }

    [Fact] // live: 19:00:05 (stored 108, right after the NULL) ⇒ null + Bad
    public async Task At_a_Good_sample_right_after_a_NULL_is_the_stored_value()
    {
        var s = (await AtTime(new AvevaStore(Gate685()).Client(), At(5))).Single();
        s.Value.ShouldBe(108d);
        s.StatusCode.ShouldBe(Good);
    }

    [Fact] // live: 99.99999999944 for a stored 100
    public async Task At_an_exact_stored_sample_is_the_exact_stored_value_without_the_Interpolated_bit()
    {
        var s = await AtTime(new AvevaStore(Gate685()).Client(), At(0), At(2));
        s[0].Value.ShouldBe(100d);
        s[0].StatusCode.ShouldBe(Good);
        s[1].Value.ShouldBe(107d);
        s[1].StatusCode.ShouldBe(Good);
    }

    [Fact] // live: no Interpolated bit
    public async Task Between_two_Good_samples_is_linear_with_the_Interpolated_bit()
    {
        var s = (await AtTime(new AvevaStore(Gate685()).Client(), At(1))).Single();
        s.Value.ShouldBe(103.5d);
        s.StatusCode.ShouldBe(GoodInterpolated);
        new Opc.Ua.StatusCode(s.StatusCode).AggregateBits.ShouldBe(Opc.Ua.AggregateBits.Interpolated);
    }

    // ---- the rest of the AtTime rules --------------------------------------------------------------------------------

    [Fact]
    public async Task Before_a_Bad_neighbour_the_previous_value_is_held_Uncertain_and_Interpolated()
    {
        var s = (await AtTime(new AvevaStore(Gate685()).Client(), At(2.5))).Single();
        s.Value.ShouldBe(107d);
        s.StatusCode.ShouldBe(UncertainInterpolated);
    }

    [Fact]
    public async Task Inside_an_outage_is_null_with_the_outages_Bad_code()
    {
        var s = (await AtTime(new AvevaStore(Gate685()).Client(), At(4))).Single();
        s.Value.ShouldBeNull();
        s.StatusCode.ShouldBe(Bad);
    }

    [Fact]
    public async Task Before_the_first_sample_is_BadNoData_not_the_boundary_rows_zero()
    {
        var s = await AtTime(new AvevaStore(Gate685()).Client(), At(-1), At(-0.001), At(-3600));
        s.ShouldAllBe(x => x.StatusCode == BadNoData && x.Value == null);
    }

    [Fact]
    public async Task After_the_last_sample_is_stepped_Good_until_now_then_Uncertain()
    {
        var s = await AtTime(new AvevaStore(Gate685()).Client(), At(10), Now.AddMinutes(5), Now.AddDays(3));
        s[0].Value.ShouldBe(108d);
        s[0].StatusCode.ShouldBe(GoodInterpolated);
        s[1].Value.ShouldBe(108d);
        s[1].StatusCode.ShouldBe(UncertainInterpolated); // later than now: not known to still hold
        s[2].Value.ShouldBe(108d);
        s[2].StatusCode.ShouldBe(UncertainInterpolated); // beyond the horizon: never sent to the gateway (it refuses)
    }

    [Fact]
    public async Task A_mixed_request_keeps_order_and_duplicates()
    {
        var s = await AtTime(new AvevaStore(Gate685()).Client(), At(5), At(1), At(-1), At(3), At(1), At(2.5));
        s.Select(x => x.Value).ShouldBe(new object?[] { 108d, 103.5d, null, null, 103.5d, 107d });
        s.Select(x => x.StatusCode).ShouldBe(new[] { Good, GoodInterpolated, BadNoData, Bad, GoodInterpolated, UncertainInterpolated });
    }

    [Fact]
    public async Task An_empty_request_reads_nothing()
    {
        var fake = new AvevaStore(Gate685()).Client();
        (await Source(fake).ReadAtTimeAsync("T", [], Ct)).Samples.ShouldBeEmpty();
        fake.ReadRawCallCount.ShouldBe(0);
    }

    [Fact]
    public async Task A_sub_millisecond_request_time_interpolates_between_the_millisecond_samples()
    {
        var s = (await AtTime(new AvevaStore(Gate685()).Client(), At(0.0005))).Single();
        ((double)s.Value!).ShouldBe(100.00175d, 1e-9);
        s.StatusCode.ShouldBe(GoodInterpolated);
    }

    [Fact]
    public async Task A_row_at_the_query_end_never_counts_as_a_stored_sample()
    {
        var store = new AvevaStore(Gate685()) { TerminalRow = true };
        var s = await AtTime(store.Client(), At(1), At(2.5), At(4), At(10));
        s.Select(x => x.Value).ShouldBe(new object?[] { 103.5d, 107d, null, 108d });
        s.Select(x => x.StatusCode).ShouldBe(new[] { GoodInterpolated, UncertainInterpolated, Bad, GoodInterpolated });
    }

    [Fact]
    public async Task A_string_tag_is_stepped()
    {
        var fake = new FakeHistorianGatewayClient
        {
            RawSource = (start, end, max) =>
            {
                var rows = new List<HistorianSample>
                {
                    new() { Tag = "T", Timestamp = Timestamp.FromDateTime(start), StringValue = "", OpcQuality = 0, Quality = 1 },
                };
                foreach (var (t, v) in new[] { (At(0), "a"), (At(10), "b") })
                    if (t >= start && t <= end)
                        rows.Add(new HistorianSample { Tag = "T", Timestamp = Timestamp.FromDateTime(t), StringValue = v, OpcQuality = 192 });
                return rows.Take(max);
            },
        };
        var s = (await AtTime(fake, At(5))).Single();
        s.Value.ShouldBe("a");
        s.StatusCode.ShouldBe(GoodInterpolated);
    }

    // ---- cost ------------------------------------------------------------------------------------------------------

    private static IEnumerable<(DateTime T, double V, bool Null)> OneHertz(DateTime from, int seconds) =>
        Enumerable.Range(0, seconds).Select(i => (from.AddSeconds(i), (double)i, false));

    [Fact]
    public async Task Ten_exact_hits_on_dense_data_are_one_read()
    {
        var fake = new AvevaStore(OneHertz(T0.AddHours(-1), 3600)).Client();
        var times = Enumerable.Range(0, 10).Select(i => T0.AddMinutes(-30).AddSeconds(i)).ToArray();
        var s = await AtTime(fake, times);
        s.Select(x => x.Value).ShouldBe(Enumerable.Range(1800, 10).Select(i => (object?)(double)i));
        s.ShouldAllBe(x => x.StatusCode == Good);
        fake.ReadRawCallCount.ShouldBe(1);
    }

    [Fact]
    public async Task Ten_interpolated_times_on_dense_data_are_three_reads()
    {
        var fake = new AvevaStore(OneHertz(T0.AddHours(-1), 3600)).Client();
        var times = Enumerable.Range(0, 10).Select(i => T0.AddMinutes(-30).AddSeconds(i + 0.5)).ToArray();
        var s = await AtTime(fake, times);
        s.Select(x => x.Value).ShouldBe(Enumerable.Range(1800, 10).Select(i => (object?)(i + 0.5)));
        s.ShouldAllBe(x => x.StatusCode == GoodInterpolated);
        fake.ReadRawCallCount.ShouldBe(3); // the window, the sample before the first time, the sample after the last
    }

    [Fact]
    public async Task Ten_times_an_hour_apart_on_dense_data_cost_about_one_read_each_not_the_rows_between()
    {
        var store = new AvevaStore(OneHertz(T0.AddHours(-12), 12 * 3600));
        var fake = store.Client();
        var times = Enumerable.Range(0, 10).Select(i => T0.AddHours(-11).AddHours(i).AddSeconds(0.5)).ToArray();
        var s = await AtTime(fake, times);
        s.Select(x => x.Value).ShouldBe(Enumerable.Range(0, 10).Select(i => (object?)(3600.0 * (i + 1) + 0.5)));
        s.ShouldAllBe(x => x.StatusCode == GoodInterpolated);
        fake.ReadRawCallCount.ShouldBe(12); // 10 window reads (each finds its own prev) + 1 walk-back + 1 probe
        store.RowsStreamed.ShouldBeLessThan(10 * 1100); // never the ~32,400 rows between the first and last time
    }

    [Fact]
    public async Task Sparse_history_far_back_is_found_in_a_bounded_number_of_reads()
    {
        var fake = new AvevaStore([(T0.AddDays(-400), 42, false), (T0.AddDays(-400).AddSeconds(10), 43, false)]).Client();
        var s = (await AtTime(fake, T0)).Single();
        s.Value.ShouldBe(43d);
        s.StatusCode.ShouldBe(GoodInterpolated);
        fake.ReadRawCallCount.ShouldBe(5); // window, 1-min + 4-min segments, the whole remainder, the probe after
    }

    [Fact]
    public async Task A_tag_with_no_history_is_BadNoData_in_a_bounded_number_of_reads()
    {
        var fake = new AvevaStore([]).Client();
        var s = await AtTime(fake, At(1), At(2));
        s.ShouldAllBe(x => x.StatusCode == BadNoData);
        fake.ReadRawCallCount.ShouldBe(4); // window, two segments, the whole remainder (no probe: nothing to interpolate)
    }

    [Fact]
    public async Task Dense_data_far_denser_than_one_read_still_finds_the_neighbours()
    {
        // 1 kHz for 10 minutes: a 1-minute walk-back segment holds 60,000 rows (truncated) — it must narrow, not fail.
        var rows = Enumerable.Range(0, 600_000).Select(i => (T0.AddMinutes(-20).AddMilliseconds(i), (double)i, false));
        var fake = new AvevaStore(rows).Client();
        var t = T0.AddMinutes(-15).AddTicks(5000); // 0.5 ms past sample 300,000
        var s = (await AtTime(fake, t)).Single();
        s.Value.ShouldBe(300_000.5d);
        s.StatusCode.ShouldBe(GoodInterpolated);
        fake.ReadRawCallCount.ShouldBe(2); // the window (holds the prev) + the probe
    }

    [Fact]
    public async Task A_walk_back_into_data_far_denser_than_one_read_narrows_instead_of_paging()
    {
        // 1 kHz for 10 minutes, then a 10-minute gap: the walk-back crosses the gap and lands in 600,000 rows.
        var rows = Enumerable.Range(0, 600_000).Select(i => (T0.AddMinutes(-20).AddMilliseconds(i), (double)i, false));
        var store = new AvevaStore(rows);
        var fake = store.Client();
        var s = (await AtTime(fake, T0.AddMinutes(-5))).Single();
        s.Value.ShouldBe(599_999d);
        s.StatusCode.ShouldBe(GoodInterpolated); // stepped from the last sample (before now)
        fake.ReadRawCallCount.ShouldBe(7); // window, 1m, 4m, remainder (truncated), 16m (truncated), 256 ms, probe
        store.RowsStreamed.ShouldBeLessThan(10_000);
    }

    [Fact]
    public async Task A_strict_gateway_with_a_small_ceiling_is_still_served()
    {
        var store = new AvevaStore(OneHertz(T0.AddHours(-1), 3600));
        var fake = store.Client(ceiling: 100);
        var times = Enumerable.Range(0, 10).Select(i => T0.AddMinutes(-30).AddSeconds(i * 30 + 0.5)).ToArray();
        var s = await AtTime(fake, times);
        s.Select(x => x.Value).ShouldBe(Enumerable.Range(0, 10).Select(i => (object?)(1800 + i * 30 + 0.5)));
        s.ShouldAllBe(x => x.StatusCode == GoodInterpolated);
        fake.RawCalls.Count(c => c.MaxValues > 100).ShouldBe(1); // learned once, then remembered — a short page is not an error
    }

    [Fact]
    public async Task Success_is_recorded_once()
    {
        var fake = new AvevaStore(Gate685()).Client();
        var ds = Source(fake);
        await ds.ReadAtTimeAsync("T", [At(1), At(4)], Ct);
        var h = ds.GetHealthSnapshot();
        h.TotalQueries.ShouldBe(1);
        h.TotalSuccesses.ShouldBe(1);
    }

    [Fact]
    public async Task A_gateway_fault_is_a_recorded_failure()
    {
        var fake = new AvevaStore(Gate685()).Client();
        fake.ThrowOnRead = new Grpc.Core.RpcException(new Grpc.Core.Status(Grpc.Core.StatusCode.Unavailable, "down"));
        var ds = Source(fake);
        await Should.ThrowAsync<Exception>(() => ds.ReadAtTimeAsync("T", [At(1)], Ct));
        ds.GetHealthSnapshot().TotalFailures.ShouldBe(1);
    }

    // ---- kill switch -----------------------------------------------------------------------------------------------

    [Fact]
    public async Task The_kill_switch_restores_AVEVAs_own_answer()
    {
        var fake = new AvevaStore(Gate685()).Client();
        fake.AtTimeSamples = [new HistorianSample { NumericValue = 107, OpcQuality = 192, Timestamp = Timestamp.FromDateTime(At(3)) }];
        var ds = new GatewayHistorianDataSource(fake, NullLogger<GatewayHistorianDataSource>.Instance, atTimeFromRaw: false);
        var s = (await ds.ReadAtTimeAsync("T", [At(3)], Ct)).Samples.Single();
        s.Value.ShouldBe(107d);
        fake.ReadAtTimeCallCount.ShouldBe(1);
        fake.ReadRawCallCount.ShouldBe(0);
    }
}