git.stella-ops.org/src/__Libraries/StellaOps.Facet.Tests/FacetDriftVexEmitterTests.cs

// <copyright file="FacetDriftVexEmitterTests.cs" company="StellaOps">
// Copyright (c) StellaOps. Licensed under BUSL-1.1.
// </copyright>
// Sprint: SPRINT_20260105_002_003_FACET (QTA-020)

using System.Collections.Immutable;
using Microsoft.Extensions.Time.Testing;
using Xunit;

namespace StellaOps.Facet.Tests;

/// <summary>
/// Unit tests for <see cref="FacetDriftVexEmitter"/>.
/// </summary>
[Trait("Category", "Unit")]
public sealed class FacetDriftVexEmitterTests
{
    private readonly FakeTimeProvider _timeProvider;
    private readonly FacetDriftVexEmitter _emitter;
    private readonly FacetDriftVexEmitterOptions _options;

    public FacetDriftVexEmitterTests()
    {
        _timeProvider = new FakeTimeProvider(new DateTimeOffset(2026, 1, 7, 12, 0, 0, TimeSpan.Zero));
        _options = FacetDriftVexEmitterOptions.Default;
        _emitter = new FacetDriftVexEmitter(_options, _timeProvider);
    }

    [Fact]
    public void EmitDrafts_WithNoRequiresVexFacets_ReturnsEmptyResult()
    {
        // Arrange
        var report = CreateDriftReport(QuotaVerdict.Ok);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        Assert.Equal(0, result.DraftsEmitted);
        Assert.Empty(result.Drafts);
    }

    [Fact]
    public void EmitDrafts_WithRequiresVexFacet_CreatesDraft()
    {
        // Arrange
        var report = CreateDriftReport(QuotaVerdict.RequiresVex);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        Assert.Equal(1, result.DraftsEmitted);
        Assert.Single(result.Drafts);
    }

    [Fact]
    public void EmitDrafts_DraftContainsCorrectImageDigest()
    {
        // Arrange
        var report = CreateDriftReport(QuotaVerdict.RequiresVex, imageDigest: "sha256:abc123");
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        Assert.Equal("sha256:abc123", result.ImageDigest);
        Assert.Equal("sha256:abc123", result.Drafts[0].ImageDigest);
    }

    [Fact]
    public void EmitDrafts_DraftContainsBaselineSealId()
    {
        // Arrange
        var report = CreateDriftReport(QuotaVerdict.RequiresVex, baselineSealId: "seal-xyz");
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        Assert.Equal("seal-xyz", result.BaselineSealId);
        Assert.Equal("seal-xyz", result.Drafts[0].BaselineSealId);
    }

    [Fact]
    public void EmitDrafts_DraftHasDeterministicId()
    {
        // Arrange
        var report = CreateDriftReport(QuotaVerdict.RequiresVex);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result1 = _emitter.EmitDrafts(context);
        var result2 = _emitter.EmitDrafts(context);

        // Assert
        Assert.Equal(result1.Drafts[0].DraftId, result2.Drafts[0].DraftId);
        Assert.StartsWith("vexfd-", result1.Drafts[0].DraftId);
    }

    [Fact]
    public void EmitDrafts_DraftIdsDifferForDifferentFacets()
    {
        // Arrange
        var facetDrifts = new[]
        {
            CreateFacetDrift("facet-a", QuotaVerdict.RequiresVex),
            CreateFacetDrift("facet-b", QuotaVerdict.RequiresVex)
        };
        var report = new FacetDriftReport
        {
            ImageDigest = "sha256:abc123",
            BaselineSealId = "seal-123",
            AnalyzedAt = _timeProvider.GetUtcNow(),
            FacetDrifts = [.. facetDrifts],
            OverallVerdict = QuotaVerdict.RequiresVex
        };
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        Assert.Equal(2, result.DraftsEmitted);
        Assert.NotEqual(result.Drafts[0].DraftId, result.Drafts[1].DraftId);
    }

    [Fact]
    public void EmitDrafts_DraftContainsChurnInformation()
    {
        // Arrange
        var report = CreateDriftReportWithChurn(25m);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        var summary = result.Drafts[0].DriftSummary;
        Assert.Equal(25m, summary.ChurnPercent);
        Assert.Equal(100, summary.BaselineFileCount);
    }

    [Fact]
    public void EmitDrafts_DraftHasCorrectExpirationTime()
    {
        // Arrange
        var options = new FacetDriftVexEmitterOptions { DraftTtl = TimeSpan.FromDays(14) };
        var emitter = new FacetDriftVexEmitter(options, _timeProvider);
        var report = CreateDriftReport(QuotaVerdict.RequiresVex);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = emitter.EmitDrafts(context);

        // Assert
        var expectedExpiry = _timeProvider.GetUtcNow().AddDays(14);
        Assert.Equal(expectedExpiry, result.Drafts[0].ExpiresAt);
    }

    [Fact]
    public void EmitDrafts_DraftHasCorrectReviewDeadline()
    {
        // Arrange
        var options = new FacetDriftVexEmitterOptions { ReviewSlaDays = 5 };
        var emitter = new FacetDriftVexEmitter(options, _timeProvider);
        var report = CreateDriftReport(QuotaVerdict.RequiresVex);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = emitter.EmitDrafts(context);

        // Assert
        var expectedDeadline = _timeProvider.GetUtcNow().AddDays(5);
        Assert.Equal(expectedDeadline, result.Drafts[0].ReviewDeadline);
    }

    [Fact]
    public void EmitDrafts_DraftRequiresReview()
    {
        // Arrange
        var report = CreateDriftReport(QuotaVerdict.RequiresVex);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        Assert.True(result.Drafts[0].RequiresReview);
    }

    [Fact]
    public void EmitDrafts_DraftHasEvidenceLinks()
    {
        // Arrange
        var report = CreateDriftReportWithChanges(added: 5, removed: 3, modified: 2);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        var links = result.Drafts[0].EvidenceLinks;
        Assert.Contains(links, l => l.Type == "facet_drift_analysis");
        Assert.Contains(links, l => l.Type == "baseline_seal");
        Assert.Contains(links, l => l.Type == "added_files");
        Assert.Contains(links, l => l.Type == "removed_files");
        Assert.Contains(links, l => l.Type == "modified_files");
    }

    [Fact]
    public void EmitDrafts_RationaleDescribesChurn()
    {
        // Arrange - 15 files added out of 100 baseline = 15.0% churn
        var report = CreateDriftReportWithChurn(15m);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        var rationale = result.Drafts[0].Rationale;
        Assert.Contains("15.0%", rationale);
        Assert.Contains("quota", rationale, StringComparison.OrdinalIgnoreCase);
    }

    [Fact]
    public void EmitDrafts_HighChurnTriggersWarningInNotes()
    {
        // Arrange
        var options = new FacetDriftVexEmitterOptions { HighChurnThreshold = 20m };
        var emitter = new FacetDriftVexEmitter(options, _timeProvider);
        var report = CreateDriftReportWithChurn(35m);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = emitter.EmitDrafts(context);

        // Assert
        var notes = result.Drafts[0].ReviewerNotes;
        Assert.NotNull(notes);
        Assert.Contains("WARNING", notes);
        Assert.Contains("High churn", notes);
    }

    [Fact]
    public void EmitDrafts_RemovedFilesTriggersNoteInReviewerNotes()
    {
        // Arrange
        var report = CreateDriftReportWithChanges(added: 0, removed: 5, modified: 0);
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        var notes = result.Drafts[0].ReviewerNotes;
        Assert.NotNull(notes);
        Assert.Contains("removed", notes, StringComparison.OrdinalIgnoreCase);
    }

    [Fact]
    public void EmitDrafts_RespectsMaxDraftsLimit()
    {
        // Arrange
        var options = new FacetDriftVexEmitterOptions { MaxDraftsPerBatch = 2 };
        var emitter = new FacetDriftVexEmitter(options, _timeProvider);

        var facetDrifts = Enumerable.Range(0, 5)
            .Select(i => CreateFacetDrift($"facet-{i}", QuotaVerdict.RequiresVex))
            .ToImmutableArray();

        var report = new FacetDriftReport
        {
            ImageDigest = "sha256:abc123",
            BaselineSealId = "seal-123",
            AnalyzedAt = _timeProvider.GetUtcNow(),
            FacetDrifts = facetDrifts,
            OverallVerdict = QuotaVerdict.RequiresVex
        };
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = emitter.EmitDrafts(context);

        // Assert
        Assert.Equal(2, result.DraftsEmitted);
        Assert.Equal(2, result.Drafts.Length);
    }

    [Fact]
    public void EmitDrafts_SkipsNonRequiresVexFacets()
    {
        // Arrange
        var facetDrifts = new[]
        {
            CreateFacetDrift("facet-ok", QuotaVerdict.Ok),
            CreateFacetDrift("facet-warn", QuotaVerdict.Warning),
            CreateFacetDrift("facet-block", QuotaVerdict.Blocked),
            CreateFacetDrift("facet-vex", QuotaVerdict.RequiresVex)
        };

        var report = new FacetDriftReport
        {
            ImageDigest = "sha256:abc123",
            BaselineSealId = "seal-123",
            AnalyzedAt = _timeProvider.GetUtcNow(),
            FacetDrifts = [.. facetDrifts],
            OverallVerdict = QuotaVerdict.RequiresVex
        };
        var context = new FacetDriftVexEmissionContext(report);

        // Act
        var result = _emitter.EmitDrafts(context);

        // Assert
        Assert.Equal(1, result.DraftsEmitted);
        Assert.Equal("facet-vex", result.Drafts[0].FacetId);
    }

    [Fact]
    public void EmitDrafts_NullContext_ThrowsArgumentNullException()
    {
        // Act & Assert
        Assert.Throws<ArgumentNullException>(() => _emitter.EmitDrafts(null!));
    }

    #region Helper Methods

    private FacetDriftReport CreateDriftReport(
        QuotaVerdict verdict,
        string imageDigest = "sha256:default",
        string baselineSealId = "seal-default")
    {
        return new FacetDriftReport
        {
            ImageDigest = imageDigest,
            BaselineSealId = baselineSealId,
            AnalyzedAt = _timeProvider.GetUtcNow(),
            FacetDrifts = [CreateFacetDrift("test-facet", verdict)],
            OverallVerdict = verdict
        };
    }

    private FacetDriftReport CreateDriftReportWithChurn(decimal churnPercent)
    {
        var addedCount = (int)(churnPercent * 100 / 100);
        var addedFiles = Enumerable.Range(0, addedCount)
            .Select(i => new FacetFileEntry($"/added{i}.txt", $"sha256:added{i}", 100, null))
            .ToImmutableArray();

        var facetDrift = new FacetDrift
        {
            FacetId = "test-facet",
            Added = addedFiles,
            Removed = [],
            Modified = [],
            DriftScore = churnPercent,
            QuotaVerdict = QuotaVerdict.RequiresVex,
            BaselineFileCount = 100
        };

        return new FacetDriftReport
        {
            ImageDigest = "sha256:churn-test",
            BaselineSealId = "seal-churn",
            AnalyzedAt = _timeProvider.GetUtcNow(),
            FacetDrifts = [facetDrift],
            OverallVerdict = QuotaVerdict.RequiresVex
        };
    }

    private FacetDriftReport CreateDriftReportWithChanges(int added, int removed, int modified)
    {
        var addedFiles = Enumerable.Range(0, added)
            .Select(i => new FacetFileEntry($"/added{i}.txt", $"sha256:added{i}", 100, null))
            .ToImmutableArray();

        var removedFiles = Enumerable.Range(0, removed)
            .Select(i => new FacetFileEntry($"/removed{i}.txt", $"sha256:removed{i}", 100, null))
            .ToImmutableArray();

        var modifiedFiles = Enumerable.Range(0, modified)
            .Select(i => new FacetFileModification(
                $"/modified{i}.txt",
                $"sha256:old{i}",
                $"sha256:new{i}",
                100,
                110))
            .ToImmutableArray();

        var facetDrift = new FacetDrift
        {
            FacetId = "test-facet",
            Added = addedFiles,
            Removed = removedFiles,
            Modified = modifiedFiles,
            DriftScore = added + removed + modified,
            QuotaVerdict = QuotaVerdict.RequiresVex,
            BaselineFileCount = 100
        };

        return new FacetDriftReport
        {
            ImageDigest = "sha256:changes-test",
            BaselineSealId = "seal-changes",
            AnalyzedAt = _timeProvider.GetUtcNow(),
            FacetDrifts = [facetDrift],
            OverallVerdict = QuotaVerdict.RequiresVex
        };
    }

    private FacetDrift CreateFacetDrift(string facetId, QuotaVerdict verdict)
    {
        var addedCount = verdict == QuotaVerdict.RequiresVex ? 50 : 0;
        var addedFiles = Enumerable.Range(0, addedCount)
            .Select(i => new FacetFileEntry($"/added{i}.txt", $"sha256:added{i}", 100, null))
            .ToImmutableArray();

        return new FacetDrift
        {
            FacetId = facetId,
            Added = addedFiles,
            Removed = [],
            Modified = [],
            DriftScore = addedCount,
            QuotaVerdict = verdict,
            BaselineFileCount = 100
        };
    }

    #endregion
}