Track the operation owning internal errors

internal/usecase/operation_error.go

@@ -0,0 +1,38 @@
+package usecase
+
+import (
+	"errors"
+	"fmt"
+
+	"go.maximumdirect.net/promptkit/internal/profile"
+	"go.maximumdirect.net/promptkit/internal/promptdef"
+)
+
+// OperationError identifies the operation that owns a failure while retaining
+// the original cause for inspection.
+type OperationError struct {
+	Category error
+	Cause    error
+}
+
+func (e *OperationError) Error() string        { return fmt.Sprintf("%v: %v", e.Category, e.Cause) }
+func (e *OperationError) Unwrap() error        { return e.Cause }
+func (e *OperationError) Is(target error) bool { return target == e.Category }
+
+func promptLookupError(cause error) error {
+	category := ErrPromptLoad
+	if errors.Is(cause, promptdef.ErrPromptDefinitionNotFound) {
+		category = promptdef.ErrPromptDefinitionNotFound
+		cause = fmt.Errorf("%w: %w", ErrPromptLoad, cause)
+	}
+	return &OperationError{Category: category, Cause: cause}
+}
+
+func profileLookupError(cause error) error {
+	category := ErrProfileLoad
+	if errors.Is(cause, profile.ErrProfileNotFound) {
+		category = profile.ErrProfileNotFound
+		cause = fmt.Errorf("%w: %w", ErrProfileLoad, cause)
+	}
+	return &OperationError{Category: category, Cause: cause}
+}