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

src/Cli/StellaOps.Cli/Services/OciImageReferenceParser.cs

@@ -0,0 +1,141 @@
+using StellaOps.Cli.Services.Models;
+
+namespace StellaOps.Cli.Services;
+
+internal static class OciImageReferenceParser
+{
+    public static OciImageReference Parse(string reference)
+    {
+        if (string.IsNullOrWhiteSpace(reference))
+        {
+            throw new ArgumentException("Image reference is required.", nameof(reference));
+        }
+
+        reference = reference.Trim();
+        if (reference.StartsWith("http://", StringComparison.OrdinalIgnoreCase) ||
+            reference.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
+        {
+            return ParseUri(reference);
+        }
+
+        var registry = string.Empty;
+        var remainder = reference;
+        var parts = reference.Split('/', StringSplitOptions.RemoveEmptyEntries);
+
+        if (parts.Length > 1 && LooksLikeRegistry(parts[0]))
+        {
+            registry = parts[0];
+            remainder = string.Join('/', parts.Skip(1));
+        }
+        else
+        {
+            registry = "docker.io";
+        }
+
+        var repository = remainder;
+        string? tag = null;
+        string? digest = null;
+
+        var atIndex = remainder.LastIndexOf('@');
+        if (atIndex >= 0)
+        {
+            repository = remainder[..atIndex];
+            digest = remainder[(atIndex + 1)..];
+        }
+        else
+        {
+            var lastColon = remainder.LastIndexOf(':');
+            var lastSlash = remainder.LastIndexOf('/');
+            if (lastColon > lastSlash)
+            {
+                repository = remainder[..lastColon];
+                tag = remainder[(lastColon + 1)..];
+            }
+        }
+
+        if (string.IsNullOrWhiteSpace(repository))
+        {
+            throw new ArgumentException("Image repository is required.", nameof(reference));
+        }
+
+        if (string.Equals(registry, "docker.io", StringComparison.OrdinalIgnoreCase) &&
+            !repository.Contains('/', StringComparison.Ordinal))
+        {
+            repository = $"library/{repository}";
+        }
+
+        if (string.IsNullOrWhiteSpace(tag) && string.IsNullOrWhiteSpace(digest))
+        {
+            tag = "latest";
+        }
+
+        return new OciImageReference
+        {
+            Registry = registry,
+            Repository = repository,
+            Tag = tag,
+            Digest = digest,
+            Original = reference
+        };
+    }
+
+    private static OciImageReference ParseUri(string reference)
+    {
+        if (!Uri.TryCreate(reference, UriKind.Absolute, out var uri))
+        {
+            throw new ArgumentException("Invalid image reference URI.", nameof(reference));
+        }
+
+        var registry = uri.Authority;
+        var remainder = uri.AbsolutePath.Trim('/');
+
+        string? tag = null;
+        string? digest = null;
+
+        var atIndex = remainder.LastIndexOf('@');
+        if (atIndex >= 0)
+        {
+            digest = remainder[(atIndex + 1)..];
+            remainder = remainder[..atIndex];
+        }
+        else
+        {
+            var lastColon = remainder.LastIndexOf(':');
+            if (lastColon > remainder.LastIndexOf('/'))
+            {
+                tag = remainder[(lastColon + 1)..];
+                remainder = remainder[..lastColon];
+            }
+        }
+
+        if (string.Equals(registry, "docker.io", StringComparison.OrdinalIgnoreCase) &&
+            !remainder.Contains('/', StringComparison.Ordinal))
+        {
+            remainder = $"library/{remainder}";
+        }
+
+        if (string.IsNullOrWhiteSpace(tag) && string.IsNullOrWhiteSpace(digest))
+        {
+            tag = "latest";
+        }
+
+        return new OciImageReference
+        {
+            Registry = registry,
+            Repository = remainder,
+            Tag = tag,
+            Digest = digest,
+            Original = reference
+        };
+    }
+
+    private static bool LooksLikeRegistry(string value)
+    {
+        if (string.Equals(value, "localhost", StringComparison.OrdinalIgnoreCase))
+        {
+            return true;
+        }
+
+        return value.Contains('.', StringComparison.Ordinal) || value.Contains(':', StringComparison.Ordinal);
+    }
+}