ScadaBridge/tests/ZB.MOM.WW.ScadaBridge.Commons.Tests/Debugging/FlowTraceCollectorTests.cs

using ZB.MOM.WW.Audit;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Audit;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Debugging;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;

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

/// <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(),
    };

    /// <summary>Low-priority-lane helper (D7, 2026-09-09): a canonical row built through the
    /// factory, so <c>DetailsJson</c> carries a real envelope around <paramref name="details"/>.</summary>
    private static AuditEvent Evt(string? details = null) => ScadaBridgeAuditEventFactory.Create(
        AuditChannel.ScriptTrace, AuditKind.ScriptRun, AuditStatus.Delivered,
        target: "S", requestSummary: details);

    /// <summary>Verifies that add, when beyond cap, keeps first n and flags truncated.</summary>
    [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);
    }

    /// <summary>Verifies that snapshot, when is a copy, in emission order.</summary>
    [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));
    }

    /// <summary>Verifies that concurrent adds, when never throw, and never exceed cap.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [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);
    }

    /// <summary>Verifies that default cap, when is 500, and non-positive cap is rejected.</summary>
    [Fact]
    public void DefaultCap_Is500_AndNonPositiveCapIsRejected()
    {
        Assert.Equal(500, FlowTraceCollector.DefaultMaxEvents);
        Assert.Throws<ArgumentOutOfRangeException>(() => new FlowTraceCollector(0));
    }

    /// <summary>Verifies that complete, when closes the collector, later adds are ignored and never truncate.</summary>
    [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
    }

    /// <summary>
    /// Arch-review F1: the inline copy must be the SAME filtered record the writer persists —
    /// the collector applies the redactor itself rather than handing on the raw event.
    /// </summary>
    [Fact]
    public void Add_AppliesTheRedactor_SoTheInlineCopyIsTheFilteredEvent()
    {
        var c = new FlowTraceCollector(redactor: new UpperRedactor());
        var evt = Evt(1) with { DetailsJson = "{\"secret\":\"abc\"}" };

        c.Add(evt);

        var stored = Assert.Single(c.Complete());
        Assert.Equal("{\"SECRET\":\"ABC\"}", stored.DetailsJson);
        Assert.NotSame(evt, stored);
    }

    /// <summary>
    /// Arch-review F1: the 500-event cap alone does not bound the gRPC reply the inline copy
    /// rides on — a byte budget over the redacted <c>DetailsJson</c> truncates first.
    /// </summary>
    [Fact]
    public void Add_OverByteBudget_Truncates_KeepsEarlierEvents()
    {
        var c = new FlowTraceCollector(maxEvents: 500, maxBytes: 100);
        var big = Evt(1) with { DetailsJson = new string('x', 80) };
        var big2 = Evt(2) with { DetailsJson = new string('y', 80) };

        c.Add(big);
        c.Add(big2);

        Assert.True(c.Truncated);
        Assert.Single(c.Complete());
    }

    /// <summary>The byte budget has a documented default and is validated like the event cap.</summary>
    [Fact]
    public void DefaultByteBudget_Is1Mb_AndNonPositiveBudgetIsRejected()
    {
        Assert.Equal(1_048_576, FlowTraceCollector.DefaultMaxBytes);
        Assert.Throws<ArgumentOutOfRangeException>(() => new FlowTraceCollector(maxBytes: 0));
    }

    /// <summary>D7 (2026-09-09): the low-priority lane stops short of the event cap so the
    /// step rows a run emits at the end always have room.</summary>
    [Fact]
    public void Add_LowPriority_StopsBeforeTheReserve_AndSetsLogsTruncated()
    {
        var c = new FlowTraceCollector(maxEvents: 60, maxBytes: 1_000_000); // reserve = 50 → low-priority stops at 10
        for (var i = 0; i < 12; i++) c.Add(Evt(), lowPriority: true);

        Assert.Equal(10, c.Count);
        Assert.True(c.LogsTruncated);
        Assert.False(c.Truncated);

        c.Add(Evt()); // a step row still fits

        Assert.Equal(11, c.Count);
    }

    /// <summary>D7 (2026-09-09): the low-priority lane also stops short of the byte budget.</summary>
    [Fact]
    public void Add_LowPriority_RespectsByteShare()
    {
        var c = new FlowTraceCollector(maxEvents: 500, maxBytes: 1_000); // 75% = 750 chars
        c.Add(Evt(details: new string('x', 600)), lowPriority: true);
        c.Add(Evt(details: new string('x', 200)), lowPriority: true);

        Assert.Equal(1, c.Count);
        Assert.True(c.LogsTruncated);
    }

    /// <summary>D7 (2026-09-09): the reserve floors at 1, so a tiny cap still admits one log line.</summary>
    [Fact]
    public void Add_LowPriority_WithTinyCap_StillAllowsOne()
    {
        var c = new FlowTraceCollector(maxEvents: 20, maxBytes: 1_000_000); // max(1, 20-50) = 1

        c.Add(Evt(), lowPriority: true);
        Assert.Equal(1, c.Count);
        Assert.False(c.LogsTruncated);

        c.Add(Evt(), lowPriority: true);
        Assert.Equal(1, c.Count);
        Assert.True(c.LogsTruncated);
    }

    /// <summary>D7 (2026-09-09): <see cref="FlowTraceCollector.Complete"/> closes the low-priority
    /// lane too — a late log line is dropped silently, not counted as truncated.</summary>
    [Fact]
    public void Add_LowPriority_IsNoOpAfterComplete()
    {
        var c = new FlowTraceCollector();
        c.Add(Evt(), lowPriority: true);
        c.Complete();

        c.Add(Evt(), lowPriority: true);

        Assert.Equal(1, c.Count);
        Assert.False(c.LogsTruncated);
    }

    /// <summary>Upper-cases <c>DetailsJson</c> so a test can see the filtered copy land.</summary>
    private sealed class UpperRedactor : IAuditRedactor
    {
        /// <summary>Applies the upper-casing redaction.</summary>
        /// <param name="rawEvent">The raw event.</param>
        /// <returns>The event with upper-cased details.</returns>
        public AuditEvent Apply(AuditEvent rawEvent)
            => rawEvent with { DetailsJson = rawEvent.DetailsJson?.ToUpperInvariant() };
    }

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