sprints work

src/__Libraries/StellaOps.Resolver/VerdictDelta.cs

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+/**
+ * Verdict Delta Detection
+ * Sprint: SPRINT_9100_0002_0002 (Per-Node VerdictDigest)
+ * Tasks: VDIGEST-9100-006 through VDIGEST-9100-015
+ *
+ * Provides delta detection between resolution results.
+ */
+
+using System.Collections.Immutable;
+
+namespace StellaOps.Resolver;
+
+/// <summary>
+/// Delta between two resolution results at the verdict level.
+/// </summary>
+/// <param name="ChangedVerdicts">Verdicts where the digest changed (same node, different verdict).</param>
+/// <param name="AddedVerdicts">Verdicts for nodes that are only in the new result.</param>
+/// <param name="RemovedVerdicts">Verdicts for nodes that are only in the old result.</param>
+public sealed record VerdictDelta(
+    ImmutableArray<(Verdict Old, Verdict New)> ChangedVerdicts,
+    ImmutableArray<Verdict> AddedVerdicts,
+    ImmutableArray<Verdict> RemovedVerdicts)
+{
+    /// <summary>
+    /// Returns true if there are no differences.
+    /// </summary>
+    public bool IsEmpty => ChangedVerdicts.IsEmpty && AddedVerdicts.IsEmpty && RemovedVerdicts.IsEmpty;
+}
+
+/// <summary>
+/// Interface for detecting verdict deltas.
+/// </summary>
+public interface IVerdictDeltaDetector
+{
+    /// <summary>
+    /// Detects differences between two resolution results.
+    /// </summary>
+    VerdictDelta Detect(ResolutionResult old, ResolutionResult @new);
+}
+
+/// <summary>
+/// Default verdict delta detector.
+/// </summary>
+public sealed class DefaultVerdictDeltaDetector : IVerdictDeltaDetector
+{
+    public VerdictDelta Detect(ResolutionResult old, ResolutionResult @new)
+    {
+        ArgumentNullException.ThrowIfNull(old);
+        ArgumentNullException.ThrowIfNull(@new);
+
+        var oldVerdicts = old.Verdicts.ToDictionary(v => v.Node);
+        var newVerdicts = @new.Verdicts.ToDictionary(v => v.Node);
+
+        var changed = new List<(Verdict Old, Verdict New)>();
+        var added = new List<Verdict>();
+        var removed = new List<Verdict>();
+
+        // Find changed and removed
+        foreach (var (nodeId, oldVerdict) in oldVerdicts)
+        {
+            if (newVerdicts.TryGetValue(nodeId, out var newVerdict))
+            {
+                if (oldVerdict.VerdictDigest != newVerdict.VerdictDigest)
+                {
+                    changed.Add((oldVerdict, newVerdict));
+                }
+            }
+            else
+            {
+                removed.Add(oldVerdict);
+            }
+        }
+
+        // Find added
+        foreach (var (nodeId, newVerdict) in newVerdicts)
+        {
+            if (!oldVerdicts.ContainsKey(nodeId))
+            {
+                added.Add(newVerdict);
+            }
+        }
+
+        return new VerdictDelta(
+            changed.ToImmutableArray(),
+            added.ToImmutableArray(),
+            removed.ToImmutableArray());
+    }
+}
+
+/// <summary>
+/// Human-readable diff report for verdict changes.
+/// </summary>
+public sealed record VerdictDiffReport(
+    ImmutableArray<VerdictDiffEntry> Entries);
+
+/// <summary>
+/// Single entry in a verdict diff report.
+/// </summary>
+/// <param name="NodeId">The node that changed.</param>
+/// <param name="ChangeType">Type of change (Changed, Added, Removed).</param>
+/// <param name="OldStatus">Old verdict status (if applicable).</param>
+/// <param name="NewStatus">New verdict status (if applicable).</param>
+/// <param name="OldDigest">Old verdict digest.</param>
+/// <param name="NewDigest">New verdict digest.</param>
+public sealed record VerdictDiffEntry(
+    string NodeId,
+    string ChangeType,
+    string? OldStatus,
+    string? NewStatus,
+    string? OldDigest,
+    string? NewDigest);
+
+/// <summary>
+/// Interface for generating verdict diff reports.
+/// </summary>
+public interface IVerdictDiffReporter
+{
+    /// <summary>
+    /// Generates a diff report from a verdict delta.
+    /// </summary>
+    VerdictDiffReport GenerateReport(VerdictDelta delta);
+}
+
+/// <summary>
+/// Default verdict diff reporter.
+/// </summary>
+public sealed class DefaultVerdictDiffReporter : IVerdictDiffReporter
+{
+    public VerdictDiffReport GenerateReport(VerdictDelta delta)
+    {
+        var entries = new List<VerdictDiffEntry>();
+
+        foreach (var (old, @new) in delta.ChangedVerdicts)
+        {
+            entries.Add(new VerdictDiffEntry(
+                old.Node.Value,
+                "Changed",
+                old.Status.ToString(),
+                @new.Status.ToString(),
+                old.VerdictDigest,
+                @new.VerdictDigest));
+        }
+
+        foreach (var added in delta.AddedVerdicts)
+        {
+            entries.Add(new VerdictDiffEntry(
+                added.Node.Value,
+                "Added",
+                null,
+                added.Status.ToString(),
+                null,
+                added.VerdictDigest));
+        }
+
+        foreach (var removed in delta.RemovedVerdicts)
+        {
+            entries.Add(new VerdictDiffEntry(
+                removed.Node.Value,
+                "Removed",
+                removed.Status.ToString(),
+                null,
+                removed.VerdictDigest,
+                null));
+        }
+
+        // Sort by NodeId for determinism
+        entries.Sort((a, b) => string.Compare(a.NodeId, b.NodeId, StringComparison.Ordinal));
+
+        return new VerdictDiffReport(entries.ToImmutableArray());
+    }
+}