Refactor code structure for improved readability and maintainability; optimize performance in key functions.

src/__Libraries/StellaOps.Testing.Manifests/Validation/RunManifestValidator.cs

@@ -0,0 +1,64 @@
+using System.Text.Json;
+using Json.Schema;
+using StellaOps.Testing.Manifests.Models;
+using StellaOps.Testing.Manifests.Serialization;
+
+namespace StellaOps.Testing.Manifests.Validation;
+
+/// <summary>
+/// Validates RunManifest instances against schema and invariants.
+/// </summary>
+public sealed class RunManifestValidator : IRunManifestValidator
+{
+    private readonly JsonSchema _schema;
+
+    public RunManifestValidator()
+    {
+        var schemaJson = SchemaLoader.LoadSchema("run-manifest.schema.json");
+        _schema = JsonSchema.FromText(schemaJson);
+    }
+
+    public ValidationResult Validate(RunManifest manifest)
+    {
+        var errors = new List<ValidationError>();
+
+        var json = RunManifestSerializer.Serialize(manifest);
+        var schemaResult = _schema.Evaluate(JsonDocument.Parse(json));
+        if (!schemaResult.IsValid)
+        {
+            foreach (var error in schemaResult.Errors)
+            {
+                errors.Add(new ValidationError("Schema", error.Message));
+            }
+        }
+
+        if (manifest.ArtifactDigests.Length == 0)
+        {
+            errors.Add(new ValidationError("ArtifactDigests", "At least one artifact required"));
+        }
+
+        if (manifest.FeedSnapshot.SnapshotAt > manifest.InitiatedAt)
+        {
+            errors.Add(new ValidationError("FeedSnapshot", "Feed snapshot cannot be after run initiation"));
+        }
+
+        if (manifest.ManifestDigest is not null)
+        {
+            var computed = RunManifestSerializer.ComputeDigest(manifest);
+            if (!string.Equals(computed, manifest.ManifestDigest, StringComparison.OrdinalIgnoreCase))
+            {
+                errors.Add(new ValidationError("ManifestDigest", "Digest mismatch"));
+            }
+        }
+
+        return new ValidationResult(errors.Count == 0, errors);
+    }
+}
+
+public interface IRunManifestValidator
+{
+    ValidationResult Validate(RunManifest manifest);
+}
+
+public sealed record ValidationResult(bool IsValid, IReadOnlyList<ValidationError> Errors);
+public sealed record ValidationError(string Field, string Message);

src/__Libraries/StellaOps.Testing.Manifests/Validation/SchemaLoader.cs

@@ -0,0 +1,27 @@
+using System.Reflection;
+
+namespace StellaOps.Testing.Manifests.Validation;
+
+internal static class SchemaLoader
+{
+    public static string LoadSchema(string fileName)
+    {
+        var assembly = Assembly.GetExecutingAssembly();
+        var resourceName = assembly.GetManifestResourceNames()
+            .FirstOrDefault(name => name.EndsWith(fileName, StringComparison.OrdinalIgnoreCase));
+
+        if (resourceName is null)
+        {
+            throw new InvalidOperationException($"Schema resource not found: {fileName}");
+        }
+
+        using var stream = assembly.GetManifestResourceStream(resourceName);
+        if (stream is null)
+        {
+            throw new InvalidOperationException($"Schema resource not available: {resourceName}");
+        }
+
+        using var reader = new StreamReader(stream);
+        return reader.ReadToEnd();
+    }
+}