Add PromptKit configuration comparison

integrations/ckprompt/adapters.go

@@ -69,7 +69,7 @@ func ConfigScope[I, S any](load func(context.Context, ckconfig.Selection, I, S)
 	scope := ckconfig.Scope[I, S]{
 		Name:       "promptkit",
 		Summary:    "PromptKit engine configuration.",
-		Operations: []ckconfig.Operation{ckconfig.Validate, ckconfig.Show, ckconfig.Sources, ckconfig.Explain},
+		Operations: []ckconfig.Operation{ckconfig.Validate, ckconfig.Show, ckconfig.Sources, ckconfig.Explain, ckconfig.Diff},
 	}
 	if load == nil {
 		return ckconfig.WithScopeError(scope, errors.New("PromptKit configuration loader is nil"))
@@ -89,9 +89,47 @@ func ConfigScope[I, S any](load func(context.Context, ckconfig.Selection, I, S)
 			Diagnostics: diagnostics,
 		}, nil
 	}
+	scope.Compare = func(ctx context.Context, request ckconfig.ComparisonRequest[I], state S) (commandkit.Acquired[[]configkit.Difference], error) {
+		if err := promptKitContextError(ctx); err != nil {
+			return commandkit.Acquired[[]configkit.Difference]{}, fmt.Errorf("PromptKit scope %q comparison before left load: %w", scope.Name, err)
+		}
+
+		_, leftInspection, leftDiagnostics, err := loadPromptKitEngine(ctx, request.Left.Selection, request.Left.Input, state, "left", load)
+		diagnostics := append([]commandkit.Diagnostic(nil), leftDiagnostics...)
+		if err != nil {
+			return commandkit.Acquired[[]configkit.Difference]{Diagnostics: diagnostics}, fmt.Errorf("PromptKit scope %q left comparison load: %w", scope.Name, err)
+		}
+
+		if err := promptKitContextError(ctx); err != nil {
+			return commandkit.Acquired[[]configkit.Difference]{Diagnostics: diagnostics}, fmt.Errorf("PromptKit scope %q comparison after left load: %w", scope.Name, err)
+		}
+
+		_, rightInspection, rightDiagnostics, err := loadPromptKitEngine(ctx, request.Right.Selection, request.Right.Input, state, "right", load)
+		diagnostics = append(diagnostics, rightDiagnostics...)
+		if err != nil {
+			return commandkit.Acquired[[]configkit.Difference]{Diagnostics: diagnostics}, fmt.Errorf("PromptKit scope %q right comparison load: %w", scope.Name, err)
+		}
+
+		if err := promptKitContextError(ctx); err != nil {
+			return commandkit.Acquired[[]configkit.Difference]{Diagnostics: diagnostics}, fmt.Errorf("PromptKit scope %q comparison before native diff: %w", scope.Name, err)
+		}
+
+		differences, err := leftInspection.Diff(rightInspection)
+		if err != nil {
+			return commandkit.Acquired[[]configkit.Difference]{Diagnostics: diagnostics}, fmt.Errorf("PromptKit scope %q native configuration diff: %w", scope.Name, err)
+		}
+		return commandkit.Acquired[[]configkit.Difference]{Value: differences, Diagnostics: diagnostics}, nil
+	}
 	return scope
 }
 
+func promptKitContextError(ctx context.Context) error {
+	if ctx == nil {
+		return nil
+	}
+	return ctx.Err()
+}
+
 // FromEngine creates named prompt and profile inspection callbacks backed by a
 // PromptKit engine loader. It does not call the loader during construction. Each
 // selected inspection passes its context, supplied selection, initialized input,