using System.Security.Claims;
using System.Text.Json;
using Akka.Actor;
using Microsoft.AspNetCore.Components.Authorization;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using NSubstitute;
using ZB.MOM.WW.Audit;
using ZB.MOM.WW.ScadaBridge.CentralUI.Services;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.InboundApi;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Instances;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Templates;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.Audit;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.Management;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.Notification;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Audit;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Debugging;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
using ZB.MOM.WW.ScadaBridge.Commons.Types;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Flattening;
using ZB.MOM.WW.ScadaBridge.Communication;
using ZB.MOM.WW.ScadaBridge.DeploymentManager;
using ZB.MOM.WW.ScadaBridge.ManagementService;
using ZB.MOM.WW.ScadaBridge.ScriptAnalysis;
using ZB.MOM.WW.ScadaBridge.Security;

namespace ZB.MOM.WW.ScadaBridge.CentralUI.Tests.Services;

/// <summary>
/// Tests for <see cref="FlowDebugService"/> (Flow Debugger design 2026-09-05 §5.5/§7.1):
/// the management-command bridge (holder null, error mapping, success → graph), the
/// prediction resolver wiring over substituted repositories, the script entry (design
/// 2026-09-08 §5 — script list, prediction and run over the flattened configuration), and
/// the Retry/Discard relay for a parked outbound node (follow-ups plan 2026-09-06 D4).
/// </summary>
/// <remarks>
/// <see cref="CommunicationService"/> is a concrete class with non-virtual methods, so the
/// relay tests wire its two central-local proxies (<c>SetSiteCallAudit</c> /
/// <c>SetNotificationOutbox</c>) to scripted <see cref="ReceiveActor"/>s on the test's
/// <see cref="ActorSystem"/> — the same seam <c>SiteCallsReportPageTests</c> and
/// <c>NotificationReportPageTests</c> use.
/// </remarks>
public sealed class FlowDebugServiceTests : IDisposable
{
    private static readonly JsonSerializerOptions ServerJson = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull,
    };

    private readonly ActorSystem _system = ActorSystem.Create("flow-debug-service-tests");
    private readonly IInboundApiRepository _inboundApi = Substitute.For<IInboundApiRepository>();
    private readonly ITemplateEngineRepository _templates = Substitute.For<ITemplateEngineRepository>();
    private readonly IFlatteningPipeline _pipeline = Substitute.For<IFlatteningPipeline>();
    private readonly List<ManagementEnvelope> _received = new();

    // Relay probes: everything the scripted Site Call Audit / Notification Outbox actors receive.
    private readonly List<object> _siteCallRequests = new();
    private readonly List<object> _outboxRequests = new();

    // Scripted relay replies — overridable per test before the relay call.
    private SiteCallRelayOutcome _siteCallOutcome = SiteCallRelayOutcome.Applied;
    private bool _siteReachable = true;
    private string? _siteCallError;

    public void Dispose() => _system.Terminate().Wait(TimeSpan.FromSeconds(5));

    private FlowDebugService CreateService(object? reply, string role = "Deployer")
    {
        var holder = new ManagementActorHolder();
        if (reply != null)
            holder.ActorRef = _system.ActorOf(Props.Create(() => new ScriptedManagementActor(reply, _received)));

        var claims = new[]
        {
            new Claim(JwtTokenService.UsernameClaimType, "tester"),
            new Claim(JwtTokenService.RoleClaimType, role),
        };
        var principal = new ClaimsPrincipal(new ClaimsIdentity(claims, "TestAuth"));

        var comms = new CommunicationService(
            Options.Create(new CommunicationOptions()),
            NullLogger<CommunicationService>.Instance);
        comms.SetSiteCallAudit(_system.ActorOf(Props.Create(() => new ScriptedSiteCallAuditActor(this))));
        comms.SetNotificationOutbox(_system.ActorOf(Props.Create(() => new ScriptedOutboxActor(this))));

        return new FlowDebugService(holder, new StubAuth(principal), _inboundApi, _templates, _pipeline, comms, NullLogger<FlowDebugService>.Instance);
    }

    /// <summary>
    /// Wires the instance row plus the flattened configuration its scripts are read from
    /// (script entry, design 2026-09-08 §2 — the picker and the prediction both go through
    /// <see cref="IFlatteningPipeline"/>, never the raw template chain).
    /// </summary>
    private void WireFlattened(int instanceId, string uniqueName, params ResolvedScript[] scripts)
    {
        _templates.GetInstanceByIdAsync(instanceId, Arg.Any<CancellationToken>())
            .Returns(new Instance(uniqueName) { Id = instanceId, TemplateId = 10, SiteId = 1 });
        var cfg = new FlattenedConfiguration { InstanceUniqueName = uniqueName, TemplateId = 10, SiteId = 1, Scripts = scripts };
        _pipeline.FlattenAndValidateAsync(instanceId, Arg.Any<CancellationToken>(), false, null)
            .Returns(Result<FlatteningPipelineResult>.Success(new FlatteningPipelineResult(cfg, "h", new ValidationResult())));
    }

    /// <summary>An External-lane step as <c>FlowStepProjector</c> would project it (positional per <see cref="FlowStep"/>).</summary>
    private static FlowStep OutboundStep(FlowStepKind kind, FlowStepOutcome outcome, Guid? correlationId, string? siteId)
        => new(
            Guid.NewGuid(), Guid.NewGuid(), null, kind, FlowLane.External,
            "ERP.GetOrder", null, DateTimeOffset.UtcNow, null, outcome,
            null, null, null, siteId, "node-a", "Sim01", "ERP.GetOrder", null,
            Lifecycle: null, CorrelationId: correlationId);

    [Fact]
    public async Task RetryOutbound_ApiCallParked_RelaysRetrySiteCallWithCorrelationAndSite()
    {
        var c = Guid.NewGuid();
        var svc = CreateService(reply: null);

        var result = await svc.RetryOutboundAsync(OutboundStep(FlowStepKind.ApiCall, FlowStepOutcome.Parked, c, "site-a"));

        Assert.True(result.Success, result.Message);
        Assert.Contains("relayed", result.Message);
        Assert.Contains("site-a", result.Message);
        var request = Assert.IsType<RetrySiteCallRequest>(Assert.Single(_siteCallRequests));
        Assert.Equal(c, request.TrackedOperationId);
        Assert.Equal("site-a", request.SourceSite);
        Assert.Equal("tester", request.RequestedBy);
        Assert.Empty(_outboxRequests);
    }

    [Fact]
    public async Task RetryOutbound_Notify_RelaysRetryNotification()
    {
        var c = Guid.NewGuid();
        var svc = CreateService(reply: null);

        var result = await svc.RetryOutboundAsync(OutboundStep(FlowStepKind.Notify, FlowStepOutcome.Parked, c, siteId: null));

        Assert.True(result.Success, result.Message);
        Assert.Contains("re-queued", result.Message);
        var request = Assert.IsType<RetryNotificationRequest>(Assert.Single(_outboxRequests));
        Assert.Equal(c.ToString("N"), request.NotificationId);
        Assert.Equal("tester", request.RequestedBy);
        Assert.Empty(_siteCallRequests);
    }

    [Fact]
    public async Task DiscardOutbound_DbCall_RelaysDiscardSiteCall()
    {
        var c = Guid.NewGuid();
        var svc = CreateService(reply: null);

        var result = await svc.DiscardOutboundAsync(OutboundStep(FlowStepKind.DbCall, FlowStepOutcome.Parked, c, "site-b"));

        Assert.True(result.Success, result.Message);
        Assert.Contains("Discard of", result.Message);
        Assert.Contains("site-b", result.Message);
        var request = Assert.IsType<DiscardSiteCallRequest>(Assert.Single(_siteCallRequests));
        Assert.Equal(c, request.TrackedOperationId);
        Assert.Equal("site-b", request.SourceSite);
        Assert.Equal("tester", request.RequestedBy);
    }

    [Fact]
    public async Task RetryOutbound_NotParked_RefusesWithoutRelay()
    {
        var svc = CreateService(reply: null);

        var result = await svc.RetryOutboundAsync(OutboundStep(FlowStepKind.ApiCall, FlowStepOutcome.Ok, Guid.NewGuid(), "site-a"));

        Assert.False(result.Success);
        Assert.Contains("not parked", result.Message);
        Assert.Empty(_siteCallRequests);
        Assert.Empty(_outboxRequests);
    }

    [Fact]
    public async Task RetryOutbound_NoCorrelation_Refuses()
    {
        var svc = CreateService(reply: null);

        var result = await svc.RetryOutboundAsync(OutboundStep(FlowStepKind.ApiCall, FlowStepOutcome.Parked, correlationId: null, "site-a"));

        Assert.False(result.Success);
        Assert.Contains("no tracked operation id", result.Message);
        Assert.Empty(_siteCallRequests);
        Assert.Empty(_outboxRequests);
    }

    [Fact]
    public async Task RetryOutbound_SiteKindWithoutSiteId_Refuses()
    {
        var svc = CreateService(reply: null);

        var result = await svc.RetryOutboundAsync(OutboundStep(FlowStepKind.DbCall, FlowStepOutcome.Parked, Guid.NewGuid(), siteId: " "));

        Assert.False(result.Success);
        Assert.Contains("owning site", result.Message);
        Assert.Empty(_siteCallRequests);
        Assert.Empty(_outboxRequests);
    }

    [Fact]
    public async Task RetryOutbound_NonOutboundStep_Refuses()
    {
        var svc = CreateService(reply: null);

        var result = await svc.RetryOutboundAsync(OutboundStep(FlowStepKind.ScriptRun, FlowStepOutcome.Parked, Guid.NewGuid(), "site-a"));

        Assert.False(result.Success);
        Assert.Contains("Only an API call", result.Message);
        Assert.Empty(_siteCallRequests);
        Assert.Empty(_outboxRequests);
    }

    [Fact]
    public async Task RetryOutbound_SiteUnreachable_MapsToFailureMessage()
    {
        _siteCallOutcome = SiteCallRelayOutcome.SiteUnreachable;
        _siteReachable = false;
        var svc = CreateService(reply: null);

        var result = await svc.RetryOutboundAsync(OutboundStep(FlowStepKind.ApiCall, FlowStepOutcome.Parked, Guid.NewGuid(), "site-a"));

        Assert.False(result.Success);
        Assert.Contains("unreachable", result.Message);
        Assert.Single(_siteCallRequests);
    }

    [Fact]
    public async Task RetryOutbound_NotParkedAtSite_MapsToFailureMessage()
    {
        _siteCallOutcome = SiteCallRelayOutcome.NotParked;
        var svc = CreateService(reply: null);

        var result = await svc.RetryOutboundAsync(OutboundStep(FlowStepKind.ApiCall, FlowStepOutcome.Parked, Guid.NewGuid(), "site-a"));

        Assert.False(result.Success);
        Assert.Contains("no longer parked", result.Message);
    }

    [Fact]
    public async Task DiscardOutbound_OperationFailed_UsesTheSitesOwnErrorMessage()
    {
        _siteCallOutcome = SiteCallRelayOutcome.OperationFailed;
        _siteCallError = "S&F buffer is locked by a sweep.";
        var svc = CreateService(reply: null);

        var result = await svc.DiscardOutboundAsync(OutboundStep(FlowStepKind.ApiCall, FlowStepOutcome.Parked, Guid.NewGuid(), "site-a"));

        Assert.False(result.Success);
        Assert.Equal("S&F buffer is locked by a sweep.", result.Message);
        Assert.IsType<DiscardSiteCallRequest>(Assert.Single(_siteCallRequests));
    }

    private static string SuccessPayload(int events, bool completed = true, bool truncated = false)
    {
        var root = Guid.NewGuid();
        var child = Guid.NewGuid();
        var t0 = DateTime.UtcNow;
        var list = new List<AuditEvent>
        {
            ScadaBridgeAuditEventFactory.Create(AuditChannel.ApiInbound, AuditKind.InboundRequest, AuditStatus.Delivered,
                occurredAtUtc: t0, target: "POST /api/M", executionId: root, durationMs: 100,
                requestSummary: """{"MachineCode":"Z28061"}""", responseSummary: """{"Result":true}"""),
        };
        if (events > 1)
            list.Add(ScadaBridgeAuditEventFactory.Create(AuditChannel.ScriptTrace, AuditKind.RouteCall, AuditStatus.Delivered,
                occurredAtUtc: t0.AddMilliseconds(1), target: "I.S", executionId: root, durationMs: 90,
                extra: new ScriptTraceExtra { ChildExecutionId = child }.ToJson()));
        if (events > 2)
            list.Add(ScadaBridgeAuditEventFactory.Create(AuditChannel.ScriptTrace, AuditKind.ScriptRun, AuditStatus.Delivered,
                occurredAtUtc: t0.AddMilliseconds(2), target: "S", executionId: child, parentExecutionId: root,
                sourceSiteId: "site-a", sourceInstanceId: "I", durationMs: 80));

        var result = new FlowDebugRunResult(root, completed, null, null, list, truncated, t0, t0.AddSeconds(1));
        return JsonSerializer.Serialize(result, ServerJson);
    }

    [Fact]
    public async Task RunMethod_HolderNull_ReportsServiceUnavailable()
    {
        var svc = CreateService(reply: null);

        var outcome = await svc.RunMethodAsync(4, null);

        Assert.False(outcome.Success);
        Assert.Null(outcome.Graph);
        Assert.Equal("SERVICE_UNAVAILABLE", outcome.ErrorCode);
        Assert.Empty(_received);
    }

    [Fact]
    public async Task RunMethod_ManagementError_MapsCodeAndMessageVerbatim()
    {
        var svc = CreateService(new ManagementError("c", "This node is standby.", "STANDBY_NODE"));

        var outcome = await svc.RunMethodAsync(4, null);

        Assert.False(outcome.Success);
        Assert.Equal("STANDBY_NODE", outcome.ErrorCode);
        Assert.Equal("This node is standby.", outcome.Error);
    }

    [Fact]
    public async Task RunMethod_Unauthorized_MapsToUnauthorizedCode()
    {
        var svc = CreateService(new ManagementUnauthorized("c", "Deployer role required."), role: "Viewer");

        var outcome = await svc.RunMethodAsync(4, null);

        Assert.Equal("UNAUTHORIZED", outcome.ErrorCode);
        Assert.Equal("Deployer role required.", outcome.Error);
    }

    [Fact]
    public async Task RunMethod_Success_BuildsGraphWithTheReturnedSteps_AndSendsTheTypedCommandForThePrincipal()
    {
        var svc = CreateService(new ManagementSuccess("c", SuccessPayload(events: 3)));
        using var doc = JsonDocument.Parse("""{"MachineCode":"Z28061"}""");

        var outcome = await svc.RunMethodAsync(4, doc.RootElement.Clone());

        Assert.True(outcome.Success);
        Assert.NotNull(outcome.Graph);
        Assert.NotNull(outcome.Raw);
        Assert.True(outcome.Raw!.Completed);
        // 3 returned events + the synthesized Response node.
        Assert.Equal(4, outcome.Graph!.Steps.Count);
        Assert.Contains(outcome.Graph.Steps, s => s.Kind == FlowStepKind.ScriptRun && s.Lane == FlowLane.Site);

        var envelope = Assert.Single(_received);
        var cmd = Assert.IsType<FlowDebugRunMethodCommand>(envelope.Command);
        Assert.Equal(4, cmd.ApiMethodId);
        Assert.Equal("Z28061", cmd.Parameters!.Value.GetProperty("MachineCode").GetString());
        Assert.Equal("tester", envelope.User.Username);
        Assert.Contains("Deployer", envelope.User.Roles);
    }

    [Theory]
    [InlineData(180, 205)]
    [InlineData(1, 30)]
    public void RunAskTimeoutFor_IsMethodTimeoutPlusRunGracePlusClientSlack_FlooredAtMinRunAskTimeout(int timeoutSeconds, int expectedSeconds)
    {
        var timeout = FlowDebugService.RunAskTimeoutFor(timeoutSeconds);

        Assert.Equal(TimeSpan.FromSeconds(expectedSeconds), timeout);
    }

    [Fact]
    public void ValueChangeAskTimeoutFor_IsWaitSecondsPlusClientSlack()
    {
        var timeout = FlowDebugService.ValueChangeAskTimeoutFor(45);

        Assert.Equal(TimeSpan.FromSeconds(60), timeout);
    }

    [Fact]
    public async Task RunWriteKindScript_AndReplay_SendTheirCommands()
    {
        WireFlattened(7, "Sim01",
            new ResolvedScript { CanonicalName = "OnSpeed", Code = "x", TriggerType = "ValueChange", TriggerConfiguration = "{\"attributeName\":\"Speed\"}" });
        var svc = CreateService(new ManagementSuccess("c", SuccessPayload(events: 1)));
        var exec = Guid.NewGuid();

        var vc = await svc.RunScriptAsync(7, "OnSpeed", null, "42");
        var rp = await svc.ReplayAsync(exec);

        Assert.True(vc.Success);
        Assert.True(rp.Success);
        Assert.Equal(2, _received.Count);
        var vcCmd = Assert.IsType<FlowDebugRunScriptCommand>(_received[0].Command);
        Assert.Equal((7, "OnSpeed", "42"), (vcCmd.InstanceId, vcCmd.ScriptName, vcCmd.Value));
        // A write kind fires through the attribute, so it carries no parameters.
        Assert.Null(vcCmd.Parameters);
        var rpCmd = Assert.IsType<FlowDebugReplayCommand>(_received[1].Command);
        Assert.Equal(exec, rpCmd.ExecutionId);
    }

    [Fact]
    public async Task Run_TruncatedResult_FlagsTheGraph()
    {
        var svc = CreateService(new ManagementSuccess("c", SuccessPayload(events: 2, truncated: true)));

        var outcome = await svc.RunMethodAsync(4, null);

        Assert.True(outcome.Success);
        Assert.True(outcome.Graph!.Truncated);
    }

    [Fact]
    public async Task PredictMethod_ResolvesConstantRouteTargets_ThroughInstanceTemplateChain()
    {
        _inboundApi.GetApiMethodByIdAsync(4, Arg.Any<CancellationToken>())
            .Returns(new ApiMethod("Delmia", """return await Route.To("Sim01").Call("Process", new { });""") { Id = 4 });
        _templates.GetInstanceByUniqueNameAsync("Sim01", Arg.Any<CancellationToken>())
            .Returns(new Instance("Sim01") { Id = 9, TemplateId = 20, SiteId = 1 });
        // Derived template 20 has no scripts of its own; its base 10 defines Process.
        _templates.GetScriptsByTemplateIdAsync(20, Arg.Any<CancellationToken>())
            .Returns(Task.FromResult<IReadOnlyList<TemplateScript>>([]));
        _templates.GetTemplateByIdAsync(20, Arg.Any<CancellationToken>())
            .Returns(new Template("Derived") { Id = 20, ParentTemplateId = 10 });
        _templates.GetScriptsByTemplateIdAsync(10, Arg.Any<CancellationToken>())
            .Returns(Task.FromResult<IReadOnlyList<TemplateScript>>(
            [
                new TemplateScript("Process", """await Attributes.SetAsync("Cmd", 1); await Attributes.WaitAsync("Ack", true, System.TimeSpan.FromSeconds(1));""") { Id = 1, TemplateId = 10 },
            ]));
        _templates.GetTemplateByIdAsync(10, Arg.Any<CancellationToken>())
            .Returns(new Template("Base") { Id = 10, ParentTemplateId = null });

        var svc = CreateService(reply: null);
        var flow = await svc.PredictMethodAsync(4);

        Assert.Equal(
        [
            FlowStepKind.InboundRequest, FlowStepKind.RouteCall, FlowStepKind.ScriptRun,
            FlowStepKind.AttributeWrite, FlowStepKind.AttributeWait, FlowStepKind.Response,
        ], flow.Nodes.Select(n => n.Kind).ToList());
        Assert.Equal("Sim01.Process", flow.Nodes[2].Title);
        Assert.Equal("Sim01.Cmd", flow.Nodes[3].Title);
    }

    /// <summary>
    /// Regression for the 2026-09-06 circuit deadlock: <see cref="FlowDebugService.PredictMethodAsync"/>
    /// runs on Blazor Server's single-threaded renderer sync context, and the route-target resolver used
    /// to block on the repository with <c>GetAwaiter().GetResult()</c> from inside the synchronous
    /// predictor walk. A repository continuation posted back to that context could then never run —
    /// the whole circuit hung (every later click / JS-interop reply queued behind the blocked dispatcher).
    /// The pump below IS that context: one thread, posts queued, a blocked callback starves the queue.
    /// </summary>
    [Fact]
    public void PredictMethod_OnASingleThreadedSyncContext_NeverBlocksTheDispatcher()
    {
        _inboundApi.GetApiMethodByIdAsync(4, Arg.Any<CancellationToken>())
            .Returns(new ApiMethod("Delmia", """return await Route.To("Sim01").Call("Process", new { });""") { Id = 4 });
        // The instance lookup completes only after a Yield — i.e. only when the sync context gets to
        // run the continuation. Blocking on it from the context's own thread is the deadlock.
        _templates.GetInstanceByUniqueNameAsync("Sim01", Arg.Any<CancellationToken>())
            .Returns(_ => YieldThen(new Instance("Sim01") { Id = 9, TemplateId = 10, SiteId = 1 }));
        _templates.GetScriptsByTemplateIdAsync(10, Arg.Any<CancellationToken>())
            .Returns(Task.FromResult<IReadOnlyList<TemplateScript>>(
            [
                new TemplateScript("Process", """await Attributes.SetAsync("Cmd", 1);""") { Id = 1, TemplateId = 10 },
            ]));
        _templates.GetTemplateByIdAsync(10, Arg.Any<CancellationToken>())
            .Returns(new Template("Base") { Id = 10, ParentTemplateId = null });
        var svc = CreateService(reply: null);

        var pump = new SingleThreadPump();
        PredictedFlow? flow = null;
        Exception? failure = null;
        var done = new ManualResetEventSlim();
        var thread = new Thread(() =>
        {
            try { flow = pump.Run(() => svc.PredictMethodAsync(4)); }
            catch (Exception ex) { failure = ex; }
            finally { done.Set(); }
        }) { IsBackground = true, Name = "flow-predict-pump" };
        thread.Start();

        Assert.True(done.Wait(TimeSpan.FromSeconds(10)),
            "PredictMethodAsync deadlocked the single-threaded sync context (sync-over-async in the route resolver).");
        Assert.Null(failure);
        Assert.NotNull(flow);
        Assert.Contains(flow!.Nodes, n => n.Kind == FlowStepKind.ScriptRun && n.Title == "Sim01.Process");
        Assert.Contains(flow.Nodes, n => n.Kind == FlowStepKind.AttributeWrite && n.Title == "Sim01.Cmd");
    }

    [Fact]
    public async Task PredictMethod_NestedRouteTargets_ResolveAcrossPasses()
    {
        // Process calls a second script on the same instance via Scripts.Call — discovered only once
        // Process itself has been resolved, so the service needs a second resolve-and-rewalk pass.
        _inboundApi.GetApiMethodByIdAsync(4, Arg.Any<CancellationToken>())
            .Returns(new ApiMethod("Delmia", """return await Route.To("Sim01").Call("Process", new { });""") { Id = 4 });
        _templates.GetInstanceByUniqueNameAsync("Sim01", Arg.Any<CancellationToken>())
            .Returns(new Instance("Sim01") { Id = 9, TemplateId = 10, SiteId = 1 });
        _templates.GetScriptsByTemplateIdAsync(10, Arg.Any<CancellationToken>())
            .Returns(Task.FromResult<IReadOnlyList<TemplateScript>>(
            [
                new TemplateScript("Process", """await Scripts.Call("Inner", new { });""") { Id = 1, TemplateId = 10 },
                new TemplateScript("Inner", """await Attributes.SetAsync("Cmd", 1);""") { Id = 2, TemplateId = 10 },
            ]));
        _templates.GetTemplateByIdAsync(10, Arg.Any<CancellationToken>())
            .Returns(new Template("Base") { Id = 10, ParentTemplateId = null });
        var svc = CreateService(reply: null);

        var flow = await svc.PredictMethodAsync(4);

        var kinds = flow.Nodes.Select(n => n.Kind).ToList();
        Assert.Contains(FlowStepKind.AttributeWrite, kinds);
        Assert.Contains(flow.Nodes, n => n.Title == "Sim01.Inner");
        Assert.Contains(flow.Nodes, n => n.Title == "Sim01.Cmd");
    }

    private static async Task<Instance?> YieldThen(Instance instance)
    {
        await Task.Yield();
        return instance;
    }

    /// <summary>A Blazor-Server-shaped sync context: a single thread draining a queue of posted callbacks.</summary>
    private sealed class SingleThreadPump : SynchronizationContext
    {
        private readonly System.Collections.Concurrent.BlockingCollection<(SendOrPostCallback Callback, object? State)> _queue = new();

        public override void Post(SendOrPostCallback d, object? state) => _queue.Add((d, state));

        public override void Send(SendOrPostCallback d, object? state) => throw new NotSupportedException();

        public T Run<T>(Func<Task<T>> body)
        {
            var previous = Current;
            SetSynchronizationContext(this);
            try
            {
                var task = body();
                while (!task.IsCompleted)
                {
                    var (callback, state) = _queue.Take();
                    callback(state);
                }

                return task.GetAwaiter().GetResult();
            }
            finally
            {
                SetSynchronizationContext(previous);
            }
        }
    }

    [Fact]
    public async Task PredictMethod_UnknownMethod_IsEmpty()
    {
        _inboundApi.GetApiMethodByIdAsync(99, Arg.Any<CancellationToken>()).Returns((ApiMethod?)null);
        var svc = CreateService(reply: null);

        var flow = await svc.PredictMethodAsync(99);

        Assert.Empty(flow.Nodes);
    }

    [Fact]
    public async Task GetInstanceScripts_ProjectsFlattenedScripts_WithTriggerAttributeAndKind_OrderedByName()
    {
        WireFlattened(9, "Sim01",
            new ResolvedScript { CanonicalName = "Manual", Code = "return 1;", TriggerType = "Call", ParameterDefinitions = "{\"type\":\"object\"}", ExecutionTimeoutSeconds = 12 },
            new ResolvedScript { CanonicalName = "OnFlag", Code = "x", TriggerType = "valuechange", TriggerConfiguration = "{\"attributeName\":\"Flag\"}" },
            new ResolvedScript { CanonicalName = "Mod.Tick", Code = "x", TriggerType = "Interval", TriggerConfiguration = "{\"intervalMs\":1000}" });

        var options = await CreateService(reply: null).GetInstanceScriptsAsync(9);

        Assert.Equal(["Manual", "Mod.Tick", "OnFlag"], options.Select(o => o.CanonicalName).ToList());
        var onFlag = options.Single(o => o.CanonicalName == "OnFlag");
        Assert.True(onFlag.IsWriteKind); Assert.Equal("Flag", onFlag.TriggerAttribute); Assert.Equal("valuechange: Flag", onFlag.TriggerLabel);
        var manual = options.Single(o => o.CanonicalName == "Manual");
        Assert.False(manual.IsWriteKind); Assert.Equal(12, manual.ExecutionTimeoutSeconds); Assert.Equal("Call", manual.TriggerLabel);
        Assert.False(options.Single(o => o.CanonicalName == "Mod.Tick").IsWriteKind);
    }

    [Fact]
    public async Task GetInstanceScripts_UnknownInstance_IsEmpty()
    {
        Assert.Empty(await CreateService(reply: null).GetInstanceScriptsAsync(404));
    }

    [Fact]
    public async Task PredictScript_WriteKind_RootsAtTheWrite_AndAppendsTheScript()
    {
        WireFlattened(9, "Sim01",
            new ResolvedScript { CanonicalName = "OnFlag", Code = """Attributes["Ack"] = true;""", TriggerType = "ValueChange", TriggerConfiguration = "{\"attributeName\":\"Flag\"}" });

        var flow = await CreateService(reply: null).PredictScriptAsync(9, "OnFlag");

        Assert.Equal(
        [
            (FlowStepKind.AttributeWrite, "Sim01.Flag"),
            (FlowStepKind.ScriptRun, "Sim01.OnFlag"),
            (FlowStepKind.AttributeWrite, "Ack"),
        ], flow.Nodes.Select(n => (n.Kind, n.Title)).ToList());
    }

    [Fact]
    public async Task PredictScript_CallKind_RootsAtARouteCall_ThenTheScript()
    {
        WireFlattened(9, "Sim01",
            new ResolvedScript { CanonicalName = "Manual", Code = """Attributes["Ack"] = true;""", TriggerType = "Call" });

        var flow = await CreateService(reply: null).PredictScriptAsync(9, "Manual");

        Assert.Equal(FlowStepKind.RouteCall, flow.Nodes[0].Kind);
        Assert.Equal(FlowLane.Central, flow.Nodes[0].Lane);
        Assert.Equal("Sim01.Manual", flow.Nodes[0].Title);
        Assert.Equal(FlowStepKind.ScriptRun, flow.Nodes[1].Kind);
        Assert.True(flow.Edges[0].CrossesBoundary);
    }

    [Fact]
    public async Task PredictScript_UnknownScript_IsEmpty()
    {
        WireFlattened(9, "Sim01");
        Assert.Same(PredictedFlow.Empty, await CreateService(reply: null).PredictScriptAsync(9, "Nope"));
    }

    [Fact]
    public async Task RunScript_SendsTheCommand_WithTheScriptShape()
    {
        WireFlattened(9, "Sim01", new ResolvedScript { CanonicalName = "Manual", Code = "x", TriggerType = "Call", ExecutionTimeoutSeconds = 40 });
        var raw = new FlowDebugRunResult(Guid.NewGuid(), true, null, null, [], false, DateTimeOffset.UtcNow, DateTimeOffset.UtcNow);
        var svc = CreateService(reply: new ManagementSuccess("c", JsonSerializer.Serialize(raw, ServerJson)));
        using var doc = JsonDocument.Parse("""{"n":3}""");

        var outcome = await svc.RunScriptAsync(9, "Manual", doc.RootElement.Clone(), null);

        Assert.True(outcome.Success, outcome.Error);
        var env = Assert.Single(_received);
        var cmd = Assert.IsType<FlowDebugRunScriptCommand>(env.Command);
        Assert.Equal((9, "Manual"), (cmd.InstanceId, cmd.ScriptName));
        // A call kind carries its parameters verbatim and no value.
        Assert.Equal(3, cmd.Parameters!.Value.GetProperty("n").GetInt32());
        Assert.Null(cmd.Value);
    }

    /// <summary>
    /// The picker, the prediction and the run of one instance share ONE flatten for the life of
    /// the scoped service (design 2026-09-08 §5) — a regression here means every keystroke on the
    /// page re-walks the template chain.
    /// </summary>
    [Fact]
    public async Task GetInstanceScripts_ThenPredict_ThenRun_FlattenOnce()
    {
        WireFlattened(9, "Sim01", new ResolvedScript { CanonicalName = "Manual", Code = "x", TriggerType = "Call" });
        var raw = new FlowDebugRunResult(Guid.NewGuid(), true, null, null, [], false, DateTimeOffset.UtcNow, DateTimeOffset.UtcNow);
        var svc = CreateService(reply: new ManagementSuccess("c", JsonSerializer.Serialize(raw, ServerJson)));

        await svc.GetInstanceScriptsAsync(9);
        await svc.PredictScriptAsync(9, "Manual");
        await svc.RunScriptAsync(9, "Manual", null, null);

        await _pipeline.Received(1).FlattenAndValidateAsync(9, Arg.Any<CancellationToken>(), false, null);
    }

    private sealed class StubAuth : AuthenticationStateProvider
    {
        private readonly ClaimsPrincipal _user;
        public StubAuth(ClaimsPrincipal user) => _user = user;
        public override Task<AuthenticationState> GetAuthenticationStateAsync() => Task.FromResult(new AuthenticationState(_user));
    }

    private sealed class ScriptedManagementActor : ReceiveActor
    {
        public ScriptedManagementActor(object reply, List<ManagementEnvelope> received)
        {
            Receive<ManagementEnvelope>(env =>
            {
                lock (received) received.Add(env);
                Sender.Tell(reply);
            });
        }
    }

    /// <summary>Stands in for the Site Call Audit singleton proxy: records the relay request, replies as scripted.</summary>
    private sealed class ScriptedSiteCallAuditActor : ReceiveActor
    {
        public ScriptedSiteCallAuditActor(FlowDebugServiceTests test)
        {
            Receive<RetrySiteCallRequest>(r =>
            {
                lock (test._siteCallRequests) test._siteCallRequests.Add(r);
                Sender.Tell(new RetrySiteCallResponse(r.CorrelationId, test._siteCallOutcome,
                    test._siteCallOutcome == SiteCallRelayOutcome.Applied, test._siteReachable, test._siteCallError));
            });
            Receive<DiscardSiteCallRequest>(r =>
            {
                lock (test._siteCallRequests) test._siteCallRequests.Add(r);
                Sender.Tell(new DiscardSiteCallResponse(r.CorrelationId, test._siteCallOutcome,
                    test._siteCallOutcome == SiteCallRelayOutcome.Applied, test._siteReachable, test._siteCallError));
            });
        }
    }

    /// <summary>Stands in for the Notification Outbox singleton proxy: records the request, replies success.</summary>
    private sealed class ScriptedOutboxActor : ReceiveActor
    {
        public ScriptedOutboxActor(FlowDebugServiceTests test)
        {
            Receive<RetryNotificationRequest>(r =>
            {
                lock (test._outboxRequests) test._outboxRequests.Add(r);
                Sender.Tell(new RetryNotificationResponse(r.CorrelationId, true, null));
            });
            Receive<DiscardNotificationRequest>(r =>
            {
                lock (test._outboxRequests) test._outboxRequests.Add(r);
                Sender.Tell(new DiscardNotificationResponse(r.CorrelationId, true, null));
            });
        }
    }
}