using System.Collections.Concurrent;
using Serilog;
using ZB.MOM.WW.ScadaBridge.Commons.Observability;

namespace ZB.MOM.WW.ScadaBridge.Commons.Tests.Observability;

/// <summary>
/// ScadaBridge#56: the per-execution sink copies a line to the target registered for the line's
/// <c>ExecutionId</c> — and to nothing else. Each test uses fresh ids, because the registry is
/// process-wide and other tests may register concurrently.
/// </summary>
public class ExecutionLogCaptureTests
{
    private sealed class Target : IExecutionLogTarget
    {
        public ConcurrentQueue<CapturedLogLine> Lines { get; } = new();
        public Action<CapturedLogLine>? OnCapture { get; init; }

        public void Capture(CapturedLogLine line)
        {
            Lines.Enqueue(line);
            OnCapture?.Invoke(line);
        }
    }

    private static Serilog.ILogger Node() => new LoggerConfiguration()
        .MinimumLevel.Information()
        .Enrich.FromLogContext()
        .WriteTo.Sink(new ExecutionLogCaptureSink())
        .CreateLogger();

    /// <summary>A line tagged with a registered id reaches its target with level, category, text, exception and time.</summary>
    [Fact]
    public void TaggedLine_ReachesItsTarget()
    {
        var node = Node().ForContext("SourceContext", "Acme.InstanceActor");
        var id = Guid.NewGuid();
        var target = new Target();
        using var registration = ExecutionLogCapture.Register(id, target);

        using (ExecutionLogContext.Push(id))
            node.Warning(new InvalidOperationException("bad"), "wrote {Tag}", "T1");

        var line = Assert.Single(target.Lines);
        Assert.Equal("warn", line.Level);
        Assert.Equal("Acme.InstanceActor", line.Category);
        Assert.Equal("wrote \"T1\"", line.Message);
        Assert.Equal("bad", line.Exception!.Message);
        Assert.Equal(DateTimeKind.Utc, line.OccurredAtUtc.Kind);
        Assert.True(ExecutionLogCapture.HasTargets);
    }

    /// <summary>Untagged lines, lines of another execution, and lines below the node's level are not captured.</summary>
    [Fact]
    public void UntaggedOrOtherOrFilteredLines_AreNotCaptured()
    {
        var node = Node();
        var id = Guid.NewGuid();
        var target = new Target();
        using var registration = ExecutionLogCapture.Register(id, target);

        node.Information("untagged");
        using (ExecutionLogContext.Push(Guid.NewGuid()))
            node.Information("other execution");
        using (ExecutionLogContext.Push(id))
            node.Debug("below the node minimum");

        Assert.Empty(target.Lines);
    }

    /// <summary>A line written inside <see cref="ExecutionLogCapture.Suppress"/> (already a trace row) is skipped.</summary>
    [Fact]
    public void SuppressedLine_IsNotCaptured()
    {
        var node = Node();
        var id = Guid.NewGuid();
        var target = new Target();
        using var registration = ExecutionLogCapture.Register(id, target);

        using (ExecutionLogContext.Push(id))
        {
            using (ExecutionLogCapture.Suppress())
                node.Information("already a row");
            node.Information("captured");
        }

        Assert.Equal("captured", Assert.Single(target.Lines).Message);
    }

    /// <summary>A target that logs for the same execution while capturing does not loop back into itself.</summary>
    [Fact]
    public void TargetThatLogs_DoesNotRecapture()
    {
        var node = Node();
        var id = Guid.NewGuid();
        // Logs once only, so a broken guard fails this test instead of overflowing the stack.
        var logged = 0;
        var target = new Target { OnCapture = _ => { if (Interlocked.Increment(ref logged) == 1) node.Warning("emit failed"); } };
        using var registration = ExecutionLogCapture.Register(id, target);

        using (ExecutionLogContext.Push(id))
            node.Information("first");

        Assert.Equal("first", Assert.Single(target.Lines).Message);
    }

    /// <summary>A line logged on another thread that re-pushed the id (an actor serving the run) is captured.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [Fact]
    public async Task LineOnAnotherThread_WithTheIdRepushed_IsCaptured()
    {
        var node = Node();
        var id = Guid.NewGuid();
        var target = new Target();
        using var registration = ExecutionLogCapture.Register(id, target);

        await Task.Factory.StartNew(() =>
        {
            using (ExecutionLogContext.Push(id))
                node.Information("from an actor thread");
        }, CancellationToken.None, TaskCreationOptions.LongRunning, TaskScheduler.Default);

        Assert.Equal("from an actor thread", Assert.Single(target.Lines).Message);
    }

    /// <summary>Disposing removes the registration; a duplicate registration is ignored and its disposal harmless.</summary>
    [Fact]
    public void Dispose_Unregisters_AndDuplicateIsIgnored()
    {
        var node = Node();
        var id = Guid.NewGuid();
        var first = new Target();
        var second = new Target();
        var registration = ExecutionLogCapture.Register(id, first);
        ExecutionLogCapture.Register(id, second).Dispose(); // duplicate: no-op, must not remove the first

        Assert.True(ExecutionLogCapture.TryGetTarget(id, out var found));
        Assert.Same(first, found);

        registration.Dispose();
        registration.Dispose();
        Assert.False(ExecutionLogCapture.TryGetTarget(id, out _));
        using (ExecutionLogContext.Push(id))
            node.Information("after");
        Assert.Empty(first.Lines);
        Assert.Empty(second.Lines);
    }
}