sprints and audit work

src/Policy/StellaOps.Policy.Engine/Gates/Determinization/SignalSnapshotBuilder.cs

@@ -0,0 +1,95 @@
+using Microsoft.Extensions.Logging;
+using StellaOps.Policy.Determinization.Models;
+
+namespace StellaOps.Policy.Engine.Gates.Determinization;
+
+/// <summary>
+/// Builds signal snapshots for determinization evaluation by querying signal repositories.
+/// </summary>
+public sealed class SignalSnapshotBuilder : ISignalSnapshotBuilder
+{
+    private readonly ISignalRepository _signalRepository;
+    private readonly TimeProvider _timeProvider;
+    private readonly ILogger<SignalSnapshotBuilder> _logger;
+
+    public SignalSnapshotBuilder(
+        ISignalRepository signalRepository,
+        TimeProvider timeProvider,
+        ILogger<SignalSnapshotBuilder> logger)
+    {
+        _signalRepository = signalRepository;
+        _timeProvider = timeProvider;
+        _logger = logger;
+    }
+
+    public async Task<SignalSnapshot> BuildAsync(
+        string cveId,
+        string componentPurl,
+        CancellationToken ct = default)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(cveId);
+        ArgumentException.ThrowIfNullOrWhiteSpace(componentPurl);
+
+        _logger.LogDebug(
+            "Building signal snapshot for CVE {CveId} on {Purl}",
+            cveId,
+            componentPurl);
+
+        var snapshotAt = _timeProvider.GetUtcNow();
+        var subjectKey = BuildSubjectKey(cveId, componentPurl);
+
+        // Query all signals in parallel
+        var signalsTask = _signalRepository.GetSignalsAsync(subjectKey, ct);
+        var signals = await signalsTask;
+
+        // Build snapshot from retrieved signals
+        var snapshot = SignalSnapshot.Empty(cveId, componentPurl, snapshotAt);
+
+        foreach (var signal in signals)
+        {
+            snapshot = ApplySignal(snapshot, signal);
+        }
+
+        _logger.LogDebug(
+            "Built signal snapshot for CVE {CveId} on {Purl}: {SignalCount} signals present",
+            cveId,
+            componentPurl,
+            signals.Count);
+
+        return snapshot;
+    }
+
+    private static string BuildSubjectKey(string cveId, string componentPurl)
+        => $"{cveId}::{componentPurl}";
+
+    private SignalSnapshot ApplySignal(SignalSnapshot snapshot, Signal signal)
+    {
+        // This is a placeholder implementation
+        // In a real implementation, this would map Signal objects to SignalState<T> instances
+        // based on signal type and update the appropriate field in the snapshot
+
+        return snapshot;
+    }
+}
+
+/// <summary>
+/// Repository for retrieving signals.
+/// </summary>
+public interface ISignalRepository
+{
+    /// <summary>
+    /// Get all signals for the given subject key.
+    /// </summary>
+    Task<IReadOnlyList<Signal>> GetSignalsAsync(string subjectKey, CancellationToken ct = default);
+}
+
+/// <summary>
+/// Represents a signal retrieved from storage.
+/// </summary>
+public sealed record Signal
+{
+    public required string Type { get; init; }
+    public required string SubjectKey { get; init; }
+    public required DateTimeOffset ObservedAt { get; init; }
+    public required object? Evidence { get; init; }
+}