using ZB.MOM.WW.MxGateway.Client;
using ZB.MOM.WW.MxGateway.Contracts.Proto;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Config;
using ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Runtime;

namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests.Runtime;

/// <summary>
///     Live-gateway smokes for the two seams that <em>cannot</em> be faked because the MXAccess
///     session types are sealed with internal ctors — so the unit suite can only exercise them in
///     isolation (see <see cref="GatewayGalaxyDataWriterTests"/>):
///     <list type="number">
///         <item>
///             <description>
///             <b>Reopen</b> — the exact primitive sequence <c>GalaxyDriver.ReopenAsync</c> runs on a
///             reconnect (<see cref="GalaxyMxSession.RecreateAsync"/> then
///             <see cref="GatewayGalaxyDataWriter.InvalidateHandleCaches"/>): a write seeds the
///             item-handle + supervisory-advise caches, the recreate tears the session down and
///             rebuilds it against the live gateway, the caches are dropped, and a follow-up write
///             re-AddItems + re-AdviseSupervisory against the fresh session and succeeds.
///             </description>
///         </item>
///         <item>
///             <description>
///             <b>Write commit + persist</b> — a no-login (<c>WriteUserId = 0</c>) write commits to
///             the galaxy only because the writer <c>AdviseSupervisory</c>'s the handle first; proven
///             by reading the value back through a <em>brand-new</em> session (so the value came from
///             the galaxy, not a client-side echo).
///             </description>
///         </item>
///     </list>
///     <para>
///     Skip-gated: runs only when <c>MXGW_ENDPOINT</c> + <c>GALAXY_MXGW_API_KEY</c> point at a
///     reachable gateway (so CI stays green). Captured 2026-06-14 against <c>10.100.0.48:5120</c>.
///     Writes only the dedicated test attribute <c>TestMachine_002.TestFloat</c>.
///     </para>
/// </summary>
[Trait("Category", "Integration")]
public sealed class GatewayGalaxyLiveReopenAndWriteTests
{
    /// <summary>The dedicated writable Galaxy test attribute (Float, Operate) used by both smokes.</summary>
    private const string WriteRef = "TestMachine_002.TestFloat";

    [Fact]
    public async Task Live_reopen_recreates_session_and_re_establishes_write_handles()
    {
        var (endpoint, apiKey) = RequireLiveGatewayOrSkip();
        var ct = TestContext.Current.CancellationToken;
        var clientOptions = BuildClientOptions(endpoint, apiKey);

        await using var session = new GalaxyMxSession(new GalaxyMxAccessOptions(ClientName: "OtOpcUaReopenSmoke"));
        await session.ConnectAsync(clientOptions, ct);
        var writer = new GatewayGalaxyDataWriter(session, writeUserId: 0);

        // First write seeds both caches (AddItem -> item handle, AdviseSupervisory -> supervised handle).
        var first = await writer.WriteAsync(
            [new WriteRequest(WriteRef, 4242.0f)], _ => SecurityClassification.FreeAccess, ct);
        first.ShouldHaveSingleItem().StatusCode.ShouldBe(0u, "the first live write should return Good (0)");
        writer.CachedItemHandleCount.ShouldBe(1, "the write should have cached one item handle");
        writer.CachedSupervisedHandleCount.ShouldBe(1, "the write should have supervisory-advised the handle once");

        // Exactly what GalaxyDriver.ReopenAsync does on a reconnect: recreate the live session, drop the caches.
        await session.RecreateAsync(clientOptions, ct);
        writer.InvalidateHandleCaches();
        writer.CachedItemHandleCount.ShouldBe(0, "reopen must drop the stale item-handle cache");
        writer.CachedSupervisedHandleCount.ShouldBe(0, "reopen must drop the stale supervisory-advise cache");

        // A write after the reopen must re-AddItem + re-AdviseSupervisory against the fresh session and succeed —
        // proving RecreateAsync produced a working session and the writer rebuilt its handles.
        var second = await writer.WriteAsync(
            [new WriteRequest(WriteRef, 1313.0f)], _ => SecurityClassification.FreeAccess, ct);
        second.ShouldHaveSingleItem().StatusCode.ShouldBe(0u, "the post-reopen write should return Good (0)");
        writer.CachedItemHandleCount.ShouldBe(1, "the post-reopen write should re-establish the item handle");
        writer.CachedSupervisedHandleCount.ShouldBe(1, "the post-reopen write should re-advise the handle");

        TestContext.Current.SendDiagnosticMessage(
            $"reopen smoke: wrote {WriteRef}=4242 -> recreate+invalidate -> wrote 1313, both Good, handles re-established");
    }

    [Fact]
    public async Task Live_supervisory_write_commits_and_persists_to_galaxy()
    {
        var (endpoint, apiKey) = RequireLiveGatewayOrSkip();
        var ct = TestContext.Current.CancellationToken;
        var clientOptions = BuildClientOptions(endpoint, apiKey);

        // Baseline: read the current value through a fresh session so we can pick a target that
        // genuinely CHANGES it (otherwise a no-op write could falsely "persist").
        var current = await ReadbackFloatAsync(clientOptions, "OtOpcUaReadSmokeA", WriteRef,
            TimeSpan.FromSeconds(20), ct);
        var target = current is { } c && Math.Abs(c - 4242.0) < 1.0 ? 1313.0 : 4242.0;

        // Write via the production writer: no-login write that only commits because the writer
        // AdviseSupervisory's the handle first.
        await using (var writerSession = new GalaxyMxSession(new GalaxyMxAccessOptions(ClientName: "OtOpcUaWriteSmoke")))
        {
            await writerSession.ConnectAsync(clientOptions, ct);
            var writer = new GatewayGalaxyDataWriter(writerSession, writeUserId: 0);
            var results = await writer.WriteAsync(
                [new WriteRequest(WriteRef, (float)target)], _ => SecurityClassification.FreeAccess, ct);
            results.ShouldHaveSingleItem().StatusCode.ShouldBe(0u, "the supervisory write should return Good (0)");
        }

        // Persist proof: a BRAND-NEW session must read the written value back from the galaxy.
        // Poll (the worker's commit is async) — fail with the last observed value if it never lands.
        double? persisted = null;
        var deadline = DateTime.UtcNow + TimeSpan.FromSeconds(25);
        while (DateTime.UtcNow < deadline)
        {
            persisted = await ReadbackFloatAsync(clientOptions, "OtOpcUaReadSmokeB", WriteRef,
                TimeSpan.FromSeconds(15), ct);
            if (persisted is { } p && Math.Abs(p - target) < 0.5) break;
            await Task.Delay(1000, ct);
        }

        persisted.ShouldNotBeNull("a fresh session should have read a value for the test attribute");
        persisted!.Value.ShouldBe(target, 0.5,
            $"the supervisory write must persist in the galaxy (fresh-session read-back; last observed {persisted})");

        TestContext.Current.SendDiagnosticMessage(
            $"write-persist smoke: {WriteRef} {current} -> wrote {target} -> fresh-session read-back {persisted}");
    }

    private static (string Endpoint, string ApiKey) RequireLiveGatewayOrSkip()
    {
        var endpoint = Environment.GetEnvironmentVariable("MXGW_ENDPOINT");
        var apiKey = Environment.GetEnvironmentVariable("GALAXY_MXGW_API_KEY");
        if (string.IsNullOrWhiteSpace(endpoint) || string.IsNullOrWhiteSpace(apiKey))
            Assert.Skip("Set MXGW_ENDPOINT + GALAXY_MXGW_API_KEY to run the live gateway reopen/write smokes.");
        return (endpoint!, apiKey!);
    }

    private static MxGatewayClientOptions BuildClientOptions(string endpoint, string apiKey) => new()
    {
        Endpoint = new Uri(endpoint, UriKind.Absolute),
        ApiKey = apiKey,
        UseTls = false,
        ConnectTimeout = TimeSpan.FromSeconds(10),
        DefaultCallTimeout = TimeSpan.FromSeconds(30),
        StreamTimeout = TimeSpan.FromSeconds(30),
    };

    /// <summary>
    ///     Open a fresh session, subscribe to a single reference, and return the first decoded
    ///     data-change value (the subscribe snapshot reflects the galaxy's current value), or null
    ///     on timeout. A fresh session per call guarantees the value came from the galaxy.
    /// </summary>
    private static async Task<double?> ReadbackFloatAsync(
        MxGatewayClientOptions clientOptions, string clientName, string fullRef, TimeSpan timeout, CancellationToken ct)
    {
        await using var session = new GalaxyMxSession(new GalaxyMxAccessOptions(ClientName: clientName));
        await session.ConnectAsync(clientOptions, ct);
        var subscriber = new GatewayGalaxySubscriber(session);

        // First decoded data-change value, completed by the pump (an explicit TCS rather than a
        // captured local, so the value's visibility across the Task boundary is unambiguous).
        var firstValue = new TaskCompletionSource<double?>(TaskCreationOptions.RunContinuationsAsynchronously);
        using var streamCts = CancellationTokenSource.CreateLinkedTokenSource(ct);
        streamCts.CancelAfter(timeout);

        var pump = Task.Run(async () =>
        {
            try
            {
                await foreach (var ev in subscriber.StreamEventsAsync(streamCts.Token))
                {
                    // SubscribeBulk uses Advise (not AdviseBuffered), so the initial galaxy-value
                    // snapshot arrives as OnDataChange — never OnBufferedDataChange.
                    if (ev.Family != MxEventFamily.OnDataChange) continue;
                    if (MxValueDecoder.Decode(ev.Value) is not { } decoded) continue;
                    firstValue.TrySetResult(Convert.ToDouble(decoded));
                    return;
                }
            }
            catch (OperationCanceledException) { /* timeout, or stream ended */ }
            firstValue.TrySetResult(null); // timed out / stream completed without a data event
        }, ct);

        // Let the StreamEvents RPC attach before adding the subscription so the initial snapshot isn't
        // missed. bufferedUpdateIntervalMs:0 skips the superfluous SetBufferedUpdateInterval RPC — the
        // Advise-based snapshot is delivered regardless.
        await Task.Delay(250, ct);
        await subscriber.SubscribeBulkAsync([fullRef], bufferedUpdateIntervalMs: 0, ct);
        var result = await firstValue.Task;
        streamCts.Cancel(); // stop the pump's StreamEvents enumeration
        await pump;         // observe any pump exception + ensure teardown before the session disposes
        return result;
    }
}