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;
using ZB.MOM.WW.OtOpcUa.OpcUaServer;

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

/// <summary>
///     Gitea #691: Part 11 bounding values on the Gateway, composed by the server's <see cref="HistoryBounds"/> over the REAL
///     source and an AVEVA-shaped fake (the live gate's wire shape). The start bound of a forward read must be the stored
///     sample before StartTime, at ITS OWN time — never AVEVA's synthetic boundary row, which is stamped at the query start
///     and carries the value in effect there (<c>Quality = 133</c>). The Gateway reads forward only, so "at or before" is
///     served by the walk-back (<see cref="ReverseRawReader"/>), and no reverse window is ever sent.
/// </summary>
public sealed class GatewayBoundingValueTests
{
    private static CancellationToken Ct => TestContext.Current.CancellationToken;

    private static readonly DateTime T0 = new(2026, 10, 12, 18, 6, 0, DateTimeKind.Utc);
    private static readonly DateTime Now = T0.AddHours(1);

    /// <summary>The live gate's tag <c>HistGW.LiveTest.Gate681</c> (18:06:40 is a stored NULL).</summary>
    private static readonly (double Sec, double Value, bool Null)[] Gate681 =
    [
        (0, 10, false), (5, 20, false), (20, 30, false), (40, 0, true), (50, 5, false), (60, 1, false), (90, 1, false),
        (100, 7, false),
    ];

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

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

    /// <summary>The latest query end any ReadRaw was sent (a far-future end is the #691 review's risk).</summary>
    private sealed class EndProbe
    {
        public DateTime MaxEnd = DateTime.MinValue;
    }

    /// <summary>
    ///     ReadRaw over <c>[start, end]</c> ascending, capped, led by AVEVA's boundary row at the query start. A query end more
    ///     than two days past <see cref="Now"/> is REFUSED (<c>InvalidArgument</c>), modelling the unverified AVEVA behaviour
    ///     for a year-9999 end (the HistorianGateway only checks <c>start &lt;= end</c>, so it reaches AVEVA unclamped).
    /// </summary>
    private static FakeHistorianGatewayClient Aveva(EndProbe? probe = null)
    {
        var sorted = Gate681.Select(x => (T: At(x.Sec), V: x.Value, x.Null)).ToList();
        return new FakeHistorianGatewayClient
        {
            RawSource = (start, end, max) =>
            {
                if (probe is not null && end > probe.MaxEnd) probe.MaxEnd = end;
                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"));
                var rows = new List<HistorianSample>();
                if (sorted.All(d => d.T != start))
                {
                    var prior = sorted.Where(d => d.T < start).Select(d => ((DateTime T, double V, bool Null)?)d).LastOrDefault();
                    HistorianSample boundary;
                    if (prior is { } p)
                    {
                        boundary = Stored(start, p.V, p.Null);
                        if (!p.Null) boundary.Quality = 133;
                    }
                    else
                    {
                        boundary = new HistorianSample { Tag = "T", Timestamp = Timestamp.FromDateTime(start), NumericValue = 0, OpcQuality = 0, Quality = 1 };
                    }

                    rows.Add(boundary);
                }

                rows.AddRange(sorted.Where(d => d.T >= start && d.T <= end).Select(d => Stored(d.T, d.V, d.Null)));
                return max > 0 ? rows.Take(max) : rows;
            },
        };
    }

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

    [Fact]
    public async Task The_start_bound_is_the_stored_prior_sample_at_its_own_time_not_the_synthetic_row()
    {
        var bound = await HistoryBounds.StartBoundAsync(Source(Aveva()), "T", At(21), reverse: false, 65536, Now, Ct);

        bound.ShouldNotBeNull();
        bound.SourceTimestampUtc.ShouldBe(At(20)); // the synthetic row would be stamped At(21)
        bound.Value.ShouldBe(30d);
        bound.StatusCode.ShouldBe(0u);
    }

    [Fact]
    public async Task A_stored_NULL_prior_sample_is_the_start_bound_as_the_Bad_sample_it_is()
    {
        var bound = await HistoryBounds.StartBoundAsync(Source(Aveva()), "T", At(45), reverse: false, 65536, Now, Ct);

        bound!.SourceTimestampUtc.ShouldBe(At(40));
        bound.StatusCode.ShouldBe(0x80000000u);
    }

    [Fact]
    public async Task Before_the_first_sample_the_start_bound_is_not_found_at_the_start_time()
    {
        var bound = await HistoryBounds.StartBoundAsync(Source(Aveva()), "T", At(-30), reverse: false, 65536, Now, Ct);

        bound!.StatusCode.ShouldBe(Opc.Ua.StatusCodes.BadBoundNotFound);
        bound.SourceTimestampUtc.ShouldBe(At(-30));
        bound.Value.ShouldBeNull();
    }

    [Fact]
    public async Task A_sample_exactly_on_the_start_time_is_the_bound_and_already_the_data()
    {
        (await HistoryBounds.StartBoundAsync(Source(Aveva()), "T", At(20), reverse: false, 65536, Now, Ct)).ShouldBeNull();
    }

    [Fact]
    public async Task The_end_bound_is_the_first_stored_sample_at_or_after_the_end_time()
    {
        var source = Source(Aveva());
        var after = await HistoryBounds.EndBoundAsync(source, "T", HistoryBounds.For(At(0), At(41)), At(40), 65536, Now, Ct);
        after.SourceTimestampUtc.ShouldBe(At(50));
        after.Value.ShouldBe(5d);

        var missing = await HistoryBounds.EndBoundAsync(source, "T", HistoryBounds.For(At(0), At(101)), At(100), 65536, Now, Ct);
        missing.StatusCode.ShouldBe(Opc.Ua.StatusCodes.BadBoundNotFound);
        missing.SourceTimestampUtc.ShouldBe(At(101));
    }

    /// <summary>
    ///     #691 review: the at-or-after read never sends an end beyond now + <see cref="ReverseRawReader.LookAhead"/> (the
    ///     historian stores nothing further ahead), and an end bound wanted beyond that horizon is not found without a read.
    /// </summary>
    [Fact]
    public async Task The_at_or_after_read_never_asks_past_now_plus_one_day()
    {
        var probe = new EndProbe();
        var fake = Aveva(probe);
        var source = Source(fake);

        var found = await HistoryBounds.EndBoundAsync(source, "T", HistoryBounds.For(At(0), At(41)), At(40), 65536, Now, Ct);
        found.SourceTimestampUtc.ShouldBe(At(50));
        probe.MaxEnd.ShouldBeLessThanOrEqualTo(Now + ReverseRawReader.LookAhead.Add(TimeSpan.FromMilliseconds(1)));

        var calls = fake.ReadRawCallCount;
        var beyond = Now.AddDays(3);
        var missing = await HistoryBounds.EndBoundAsync(source, "T", HistoryBounds.For(At(0), beyond), At(100), 65536, Now, Ct);
        missing.StatusCode.ShouldBe(Opc.Ua.StatusCodes.BadBoundNotFound);
        missing.SourceTimestampUtc.ShouldBe(beyond);
        fake.ReadRawCallCount.ShouldBe(calls, "a bound beyond the horizon is not found without a read");
        source.GetHealthSnapshot().TotalFailures.ShouldBe(0);
    }

    [Fact]
    public async Task A_reverse_read_end_bound_walks_back_to_the_stored_sample_at_or_before_the_end_time()
    {
        var fake = Aveva();
        var bound = await HistoryBounds.EndBoundAsync(Source(fake), "T", HistoryBounds.For(At(100), At(55)), At(60), 65536, Now, Ct);

        bound.SourceTimestampUtc.ShouldBe(At(50));
        bound.Value.ShouldBe(5d);
    }
}