using System.Collections.Concurrent;
using Akka.Actor;
using Akka.Configuration;
using Akka.Event;
using Akka.TestKit.Xunit2;
using Serilog;
using Serilog.Core;
using Serilog.Events;
using ZB.MOM.WW.ScadaBridge.ClusterInfrastructure;
using ZB.MOM.WW.ScadaBridge.Commons.Observability;
using ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Logging;
using ZB.MOM.WW.ScadaBridge.Host.Actors;
using AkkaLogEvent = Akka.Event.LogEvent;
using SerilogLogEvent = Serilog.Events.LogEvent;

namespace ZB.MOM.WW.ScadaBridge.Host.Tests;

/// <summary>
/// ScadaBridge#120: Akka <c>ILoggingAdapter</c> lines reach the host's Serilog pipeline, with the
/// node enrichers and, for an execution-aware adapter, the <c>ExecutionId</c> of the message the
/// actor was serving.
/// </summary>
public class SerilogAkkaLoggerTests : TestKit
{
    private sealed class CaptureSink : ILogEventSink
    {
        public ConcurrentQueue<SerilogLogEvent> Events { get; } = new();
        public void Emit(SerilogLogEvent logEvent) => Events.Enqueue(logEvent);
    }

    /// <summary>An actor that logs through the execution-aware adapter while serving a message.</summary>
    private sealed class LoggingActor : ReceiveActor
    {
        private readonly ILoggingAdapter _log = ExecutionAwareLogging.GetLogger(Context);

        public LoggingActor()
        {
            Receive<(Guid? Id, string Text)>(m =>
            {
                using (ExecutionLogContext.Push(m.Id))
                    _log.Warning("actor line {0}", m.Text);
                Sender.Tell("done");
            });
        }
    }

    private readonly CaptureSink _sink = new();
    private readonly Serilog.ILogger _serilog;

    /// <summary>
    /// The system keeps Akka's default logger (TestKit's); each test that needs the bridge spawns a
    /// <see cref="SerilogAkkaLogger"/> over a capturing pipeline that mirrors the host's
    /// <c>ScadaBridgeLogging</c> (<c>Enrich.FromLogContext</c> plus a node property).
    /// </summary>
    public SerilogAkkaLoggerTests() : base("akka.loglevel = INFO")
    {
        _serilog = new LoggerConfiguration()
            .MinimumLevel.Information()
            .Enrich.WithProperty("NodeRole", "site-a")
            .Enrich.FromLogContext()
            .WriteTo.Sink(_sink)
            .CreateLogger();
    }

    private void StartBridge()
    {
        var bridge = Sys.ActorOf(Props.Create(() => new SerilogAkkaLogger(_serilog)));
        Sys.EventStream.Subscribe(bridge, typeof(AkkaLogEvent));
    }

    private SerilogLogEvent AwaitLine(string fragment)
    {
        SerilogLogEvent? found = null;
        AwaitCondition(() =>
        {
            found = _sink.Events.FirstOrDefault(e => e.RenderMessage().Contains(fragment, StringComparison.Ordinal));
            return found is not null;
        }, TimeSpan.FromSeconds(5));
        return found!;
    }

    private static string? Scalar(SerilogLogEvent e, string name)
        => e.Properties.TryGetValue(name, out var v) && v is ScalarValue { Value: { } x } ? x.ToString() : null;

    /// <summary>An Akka line reaches Serilog with its level, class, actor path, structured args and node enrichers.</summary>
    [Fact]
    public void AkkaLine_ReachesSerilog_WithSourceContextAndEnrichers()
    {
        StartBridge();
        var actor = Sys.ActorOf(Props.Create(() => new LoggingActor()), "plain-logger");

        actor.Tell(((Guid?)null, "alpha"));
        ExpectMsg("done");

        var line = AwaitLine("actor line");
        Assert.Equal(LogEventLevel.Warning, line.Level);
        Assert.Equal(typeof(LoggingActor).FullName, Scalar(line, "SourceContext"));
        Assert.Contains("plain-logger", Scalar(line, SerilogAkkaLogger.AkkaSourceProperty));
        Assert.Equal("site-a", Scalar(line, "NodeRole"));
        Assert.Equal("actor line \"alpha\"", line.RenderMessage());
        // The adapter's argument is a structured property, not baked into the text.
        Assert.Equal("alpha", Scalar(line, "0"));
        Assert.False(line.Properties.ContainsKey(ExecutionLogContext.ExecutionIdProperty));
    }

    /// <summary>
    /// The line logged while an execution was current carries that id, although Serilog writes it on
    /// the logger actor's thread, where the logging actor's LogContext is not in effect.
    /// </summary>
    [Fact]
    public void ExecutionAwareLine_CarriesTheExecutionId_AcrossTheLoggerHop()
    {
        StartBridge();
        var actor = Sys.ActorOf(Props.Create(() => new LoggingActor()));
        var id = Guid.NewGuid();

        actor.Tell(((Guid?)id, "beta"));
        ExpectMsg("done");

        Assert.Equal(id.ToString(), Scalar(AwaitLine("beta"), ExecutionLogContext.ExecutionIdProperty));
    }

    /// <summary>The Akka timestamp is kept, not replaced by the time the logger actor wrote the line.</summary>
    [Fact]
    public void Write_KeepsTheAkkaTimestamp_AndMapsEveryLevel()
    {
        var serilog = new LoggerConfiguration().MinimumLevel.Verbose().WriteTo.Sink(_sink).CreateLogger();
        var then = new DateTime(2026, 1, 2, 3, 4, 5, DateTimeKind.Utc);

        foreach (var (evt, expected) in new (AkkaLogEvent, LogEventLevel)[]
                 {
                     (new Debug("src", typeof(LoggingActor), "d-line"), LogEventLevel.Debug),
                     (new Info("src", typeof(LoggingActor), "i-line"), LogEventLevel.Information),
                     (new Warning("src", typeof(LoggingActor), "w-line"), LogEventLevel.Warning),
                     (new Error(new InvalidOperationException("boom"), "src", typeof(LoggingActor), "e-line"), LogEventLevel.Error),
                 })
        {
            typeof(AkkaLogEvent).GetProperty(nameof(AkkaLogEvent.Timestamp))!.SetValue(evt, then);
            SerilogAkkaLogger.Write(evt, serilog);
            var line = _sink.Events.Single(e => e.RenderMessage().Contains(evt.Message.ToString()!, StringComparison.Ordinal));
            Assert.Equal(expected, line.Level);
            Assert.Equal(new DateTimeOffset(then), line.Timestamp);
        }

        Assert.Equal("boom", _sink.Events.Single(e => e.Level == LogEventLevel.Error).Exception!.Message);
    }

    /// <summary>The Serilog minimum level applies to Akka lines as it does to every other line.</summary>
    [Fact]
    public void Write_BelowTheSerilogMinimum_IsDropped()
    {
        // _serilog's minimum is Information.
        SerilogAkkaLogger.Write(new Debug("src", typeof(LoggingActor), "debug-only"), _serilog);
        SerilogAkkaLogger.Write(new Info("src", typeof(LoggingActor), "info-kept"), _serilog);

        Assert.DoesNotContain(_sink.Events, e => e.RenderMessage().Contains("debug-only", StringComparison.Ordinal));
        Assert.Contains(_sink.Events, e => e.RenderMessage().Contains("info-kept", StringComparison.Ordinal));
    }

    /// <summary>
    /// The HOCON the host builds names this logger and keeps <c>akka.loglevel</c> at INFO, so Akka's
    /// Debug lifecycle chatter stays filtered at the adapter (no volume change from the bridge).
    /// </summary>
    [Fact]
    public void BuildHocon_NamesTheSerilogLogger_AndKeepsInfoLevel()
    {
        var hocon = AkkaHostedService.BuildHocon(
            new NodeOptions { Role = "Site", NodeHostname = "n", RemotingPort = 8082 },
            new ClusterOptions { SeedNodes = ["akka.tcp://scadabridge@n:8082"], SplitBrainResolverStrategy = "auto-down" },
            ["Site"], TimeSpan.FromSeconds(5), TimeSpan.FromSeconds(15));

        var config = ConfigurationFactory.ParseString(hocon);
        Assert.Equal([SerilogAkkaLogger.HoconTypeName], config.GetStringList("akka.loggers"));
        Assert.Equal("INFO", config.GetString("akka.loglevel"));
    }

    /// <summary>
    /// The type name in <c>akka.loggers</c> resolves and the logger completes Akka's startup
    /// handshake — a wrong name or a missing <c>LoggerInitialized</c> reply fails system creation.
    /// </summary>
    [Fact]
    public async Task ActorSystem_StartsWithTheSerilogLoggerConfigured()
    {
        var config = ConfigurationFactory.ParseString(
            $"akka.loggers = [\"{SerilogAkkaLogger.HoconTypeName}\"]\nakka.logger-startup-timeout = 5s");
        var system = ActorSystem.Create("serilog-logger-boot", config);
        try
        {
            system.Log.Info("boot line"); // must not throw; goes to the static Serilog logger
            Assert.False(system.WhenTerminated.IsCompleted);
        }
        finally
        {
            await system.Terminate();
        }
    }

    private sealed class CollectingTarget : IExecutionLogTarget
    {
        public ConcurrentQueue<CapturedLogLine> Lines { get; } = new();
        public void Capture(CapturedLogLine line) => Lines.Enqueue(line);
    }

    /// <summary>
    /// ScadaBridge#56 + #120 end to end: an Akka actor's own line, logged while it serves a traced
    /// execution, crosses the logger-actor hop and still reaches that execution's step log, with the
    /// actor's class as its category.
    /// </summary>
    [Fact]
    public void AkkaLine_ForATracedExecution_ReachesItsStepLog()
    {
        var serilog = new LoggerConfiguration()
            .Enrich.FromLogContext()
            .WriteTo.Sink(new ExecutionLogCaptureSink())
            .CreateLogger();
        var bridge = Sys.ActorOf(Props.Create(() => new SerilogAkkaLogger(serilog)));
        Sys.EventStream.Subscribe(bridge, typeof(AkkaLogEvent));
        var id = Guid.NewGuid();
        var target = new CollectingTarget();
        using var registration = ExecutionLogCapture.Register(id, target);

        Sys.ActorOf(Props.Create(() => new LoggingActor())).Tell(((Guid?)id, "gamma"));
        ExpectMsg("done");

        AwaitCondition(() => !target.Lines.IsEmpty, TimeSpan.FromSeconds(5));
        var line = Assert.Single(target.Lines);
        Assert.Equal("warn", line.Level);
        Assert.Equal(typeof(LoggingActor).FullName, line.Category);
        Assert.Equal("actor line \"gamma\"", line.Message);
    }
}