using ZB.MOM.WW.Audit;
using ZB.MOM.WW.ScadaBridge.SiteRuntime.Scripts;

namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.Scripts;

/// <summary>Flow Debugger design 2026-09-05 §5.4: the per-run inline trace sink.</summary>
public class FlowTraceCollectorTests
{
    private static AuditEvent Evt(int i) => new()
    {
        EventId = Guid.NewGuid(),
        OccurredAtUtc = DateTimeOffset.UtcNow,
        Actor = "t",
        Action = "ScriptTrace.AttributeWrite",
        Outcome = AuditOutcome.Success,
        Target = i.ToString(),
    };

    [Fact]
    public void Add_BeyondCap_KeepsFirstN_AndFlagsTruncated()
    {
        var c = new FlowTraceCollector(maxEvents: 500);
        Assert.False(c.Truncated);

        for (var i = 0; i < 501; i++) c.Add(Evt(i));

        var snap = c.Snapshot();
        Assert.Equal(500, snap.Count);
        Assert.True(c.Truncated);
        Assert.Equal("0", snap[0].Target);
        Assert.Equal("499", snap[499].Target);
    }

    [Fact]
    public void Snapshot_IsACopy_InEmissionOrder()
    {
        var c = new FlowTraceCollector();
        c.Add(Evt(1));
        var first = c.Snapshot();
        c.Add(Evt(2));

        Assert.Single(first);
        Assert.Equal(2, c.Count);
        Assert.Equal(new[] { "1", "2" }, c.Snapshot().Select(e => e.Target));
    }

    [Fact]
    public async Task ConcurrentAdds_NeverThrow_AndNeverExceedCap()
    {
        var c = new FlowTraceCollector(maxEvents: 100);
        var tasks = Enumerable.Range(0, 8).Select(t => Task.Run(() =>
        {
            for (var i = 0; i < 50; i++) c.Add(Evt(t * 100 + i));
        }));
        await Task.WhenAll(tasks);

        Assert.Equal(100, c.Snapshot().Count);
        Assert.True(c.Truncated);
    }

    [Fact]
    public void DefaultCap_Is500_AndNonPositiveCapIsRejected()
    {
        Assert.Equal(500, FlowTraceCollector.DefaultMaxEvents);
        Assert.Throws<ArgumentOutOfRangeException>(() => new FlowTraceCollector(0));
    }

    [Fact]
    public void Complete_ClosesTheCollector_LaterAddsAreIgnored_AndNeverTruncate()
    {
        var c = new FlowTraceCollector(maxEvents: 2);
        var first = NewEvent();
        c.Add(first);
        Assert.False(c.Completed);

        var snapshot = c.Complete();

        Assert.True(c.Completed);
        Assert.Same(first, Assert.Single(snapshot));
        c.Add(NewEvent());
        c.Add(NewEvent());
        c.Add(NewEvent());
        Assert.Equal(1, c.Count);
        Assert.False(c.Truncated);
        Assert.Equal(snapshot, c.Complete()); // idempotent
    }

    private static AuditEvent NewEvent() => new()
    {
        EventId = Guid.NewGuid(),
        OccurredAtUtc = DateTimeOffset.UtcNow,
        Actor = "t",
        Action = "ScriptTrace.ScriptRun",
        Outcome = AuditOutcome.Success,
        DetailsJson = "{}",
    };
}