using Opc.Ua;
using Opc.Ua.Client;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using static ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests.ServerEventRig;

namespace ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests;

/// <summary>Exercises the production session continuation store through actual HistoryRead requests.</summary>
public sealed class SessionHistoryContinuationLifecycleTests
{
    private static readonly DateTime Epoch = new(2026, 10, 1, 0, 0, 0, DateTimeKind.Utc);

    [Fact]
    public async Task Tokens_are_single_use_and_cannot_cross_sessions()
    {
        var ct = TestContext.Current.CancellationToken;
        await using var rig = await StartHistoryAsync(ct);
        using var owner = await rig.ConnectAsync(anonymous: true, ct);
        using var other = await rig.ConnectAsync(anonymous: true, ct);
        var point = (await PageAsync(owner, default, false, ct)).ContinuationPoint;
        point.IsEmpty.ShouldBeFalse();

        (await PageAsync(other, point, false, ct)).StatusCode.ShouldBe(StatusCodes.BadContinuationPointInvalid);
        var resumed = await PageAsync(owner, point, false, ct);
        resumed.StatusCode.ShouldBe(StatusCodes.Good);
        resumed.ContinuationPoint.IsEmpty.ShouldBeFalse();
        (await PageAsync(owner, point, false, ct)).StatusCode.ShouldBe(StatusCodes.BadContinuationPointInvalid);
    }

    [Fact]
    public async Task Release_consumes_a_token_and_malformed_tokens_are_rejected()
    {
        var ct = TestContext.Current.CancellationToken;
        await using var rig = await StartHistoryAsync(ct);
        using var session = await rig.ConnectAsync(anonymous: true, ct);
        var point = (await PageAsync(session, default, false, ct)).ContinuationPoint;
        point.IsEmpty.ShouldBeFalse();
        var released = await PageAsync(session, point, true, ct);
        released.StatusCode.ShouldBe(StatusCodes.Good);
        released.ContinuationPoint.IsEmpty.ShouldBeTrue();
        (await PageAsync(session, point, false, ct)).StatusCode.ShouldBe(StatusCodes.BadContinuationPointInvalid);
        (await PageAsync(session, ByteString.From(new byte[] { 1, 2, 3 }), false, ct))
            .StatusCode.ShouldBe(StatusCodes.BadContinuationPointInvalid);
    }

    [Fact]
    public async Task Session_capacity_evicts_the_oldest_point_and_keeps_the_newest()
    {
        var ct = TestContext.Current.CancellationToken;
        await using var rig = await StartHistoryAsync(ct);
        using var session = await rig.ConnectAsync(anonymous: true, ct);
        var first = (await PageAsync(session, default, false, ct)).ContinuationPoint;
        ByteString latest = default;
        // The production host retains the SDK's cap of 100; issue 101 distinct initial reads.
        for (var i = 0; i < 100; i++) latest = (await PageAsync(session, default, false, ct)).ContinuationPoint;
        latest.IsEmpty.ShouldBeFalse();
        (await PageAsync(session, first, false, ct)).StatusCode.ShouldBe(StatusCodes.BadContinuationPointInvalid);
        (await PageAsync(session, latest, false, ct)).StatusCode.ShouldBe(StatusCodes.Good);
    }

    [Fact]
    public async Task Closed_session_tokens_do_not_resume_on_a_new_session()
    {
        var ct = TestContext.Current.CancellationToken;
        await using var rig = await StartHistoryAsync(ct);
        ByteString point;
        using (var old = await rig.ConnectAsync(anonymous: true, ct))
        {
            point = (await PageAsync(old, default, false, ct)).ContinuationPoint;
            point.IsEmpty.ShouldBeFalse();
            await old.CloseAsync(ct);
        }
        using var fresh = await rig.ConnectAsync(anonymous: true, ct);
        (await PageAsync(fresh, point, false, ct)).StatusCode.ShouldBe(StatusCodes.BadContinuationPointInvalid);
    }

    private static async Task<ServerEventRig> StartHistoryAsync(CancellationToken ct)
    {
        var rig = await ServerEventRig.StartAsync("SessionHistoryLifecycle", encrypted: false, ct);
        try
        {
            var events = Enumerable.Range(0, 25)
                .Select(i => new HistoricalEvent($"e{i:00}", "src", Epoch.AddSeconds(i / 2), Epoch, "m", 500)).ToList();
            rig.Nm.HistorianDataSource = new EventHistoryPagingOverTheWireTests.SqlLikeEventSource(events);
            rig.MaterialiseNative();
            rig.Enforce(false, [Key()]);
            return rig;
        }
        catch
        {
            await rig.DisposeAsync();
            throw;
        }
    }

    private static async Task<Opc.Ua.HistoryReadResult> PageAsync(ISession session, ByteString point, bool release, CancellationToken ct)
    {
        var node = new NodeId(RawDeviceFolder, (ushort)session.NamespaceUris.GetIndex(V3NodeIds.RawNamespaceUri));
        var filter = new EventFilter
        {
            SelectClauses = [new SimpleAttributeOperand(ObjectTypeIds.BaseEventType, QualifiedName.From(BrowseNames.EventId))],
        };
        var details = new ReadEventDetails
        {
            StartTime = Epoch.AddDays(-1), EndTime = Epoch.AddDays(1), NumValuesPerNode = 10, Filter = filter,
        };
        var response = await session.HistoryReadAsync(null, new ExtensionObject(details), TimestampsToReturn.Both, release,
            [new HistoryReadValueId { NodeId = node, ContinuationPoint = point }], ct);
        return response.Results.ToList().ShouldHaveSingleItem();
    }
}