From 9ee9e844555c4584792725ddcf0083e76f9a8b71 Mon Sep 17 00:00:00 2001
From: Daniel Frey <d.frey@gmx.de>
Date: Wed, 4 Dec 2024 01:16:09 +0100
Subject: [PATCH] Cleanup

---
 include/tao/pq/parameter_traits.hpp       | 8 ++++++--
 include/tao/pq/parameter_traits_array.hpp | 8 +++++---
 include/tao/pq/parameter_traits_pair.hpp  | 6 ------
 include/tao/pq/parameter_traits_tuple.hpp | 6 ------
 include/tao/pq/result_traits_array.hpp    | 8 +++++---
 5 files changed, 16 insertions(+), 20 deletions(-)

diff --git a/include/tao/pq/parameter_traits.hpp b/include/tao/pq/parameter_traits.hpp
index 6fd101e..6271062 100644
--- a/include/tao/pq/parameter_traits.hpp
+++ b/include/tao/pq/parameter_traits.hpp
@@ -66,6 +66,11 @@ namespace tao::pq
    template< typename T >
    struct parameter_traits;
 
+   template< typename T >
+   concept parameter_type_has_element = requires( const parameter_traits< std::decay_t< T > >& t, std::string& s ) {
+      { t.template element< 0 >( s ) } -> std::same_as< void >;
+   };
+
    template< typename T >
    concept parameter_type_direct = requires( const parameter_traits< std::decay_t< T > >& t, std::string& s ) {
       { parameter_traits< std::decay_t< T > >::columns } -> std::same_as< const std::size_t& >;
@@ -74,9 +79,8 @@ namespace tao::pq
       { t.template value< 0 >() } -> std::same_as< const char* >;
       { t.template length< 0 >() } -> std::same_as< int >;
       { t.template format< 0 >() } -> std::same_as< int >;
-      { t.template element< 0 >( s ) } -> std::same_as< void >;
       { t.template copy_to< 0 >( s ) } -> std::same_as< void >;
-   };
+   } && ( ( parameter_traits< std::decay_t< T > >::columns >= 2 ) || parameter_type_has_element< T > );
 
    template<>
    struct parameter_traits< null_t >
diff --git a/include/tao/pq/parameter_traits_array.hpp b/include/tao/pq/parameter_traits_array.hpp
index 85656ce..d3871e8 100644
--- a/include/tao/pq/parameter_traits_array.hpp
+++ b/include/tao/pq/parameter_traits_array.hpp
@@ -49,7 +49,7 @@ namespace tao::pq
    namespace internal
    {
       template< typename T >
-         requires( !pq::is_array_parameter< T > ) && ( parameter_traits< T >::columns == 1 )
+         requires( !pq::is_array_parameter< T > )
       void to_array( std::string& data, const T& v )
       {
          parameter_traits< T >( v ).template element< 0 >( data );
@@ -72,10 +72,12 @@ namespace tao::pq
          }
       }
 
+      template< typename T >
+      concept array_parameter_type = ( pq::is_array_parameter< T > && ( pq::is_array_parameter< typename T::value_type > || ( parameter_traits< typename T::value_type >::columns == 1 ) ) );
+
    }  // namespace internal
 
-   template< typename T >
-      requires is_array_parameter< T >
+   template< internal::array_parameter_type T >
    struct parameter_traits< T >
    {
    private:
diff --git a/include/tao/pq/parameter_traits_pair.hpp b/include/tao/pq/parameter_traits_pair.hpp
index c444b6a..964ac07 100644
--- a/include/tao/pq/parameter_traits_pair.hpp
+++ b/include/tao/pq/parameter_traits_pair.hpp
@@ -62,12 +62,6 @@ struct tao::pq::parameter_traits< std::pair< T, U > >
       return std::get< gen::template outer< I > >( m_pair ).template format< gen::template inner< I > >();
    }
 
-   template< std::size_t I >
-   void element( std::string& data ) const
-   {
-      std::get< gen::template outer< I > >( m_pair ).template element< gen::template inner< I > >( data );
-   }
-
    template< std::size_t I >
    void copy_to( std::string& data ) const
    {
diff --git a/include/tao/pq/parameter_traits_tuple.hpp b/include/tao/pq/parameter_traits_tuple.hpp
index 07be674..41305c7 100644
--- a/include/tao/pq/parameter_traits_tuple.hpp
+++ b/include/tao/pq/parameter_traits_tuple.hpp
@@ -61,12 +61,6 @@ struct tao::pq::parameter_traits< std::tuple< Ts... > >
       return std::get< gen::template outer< I > >( m_tuple ).template format< gen::template inner< I > >();
    }
 
-   template< std::size_t I >
-   void element( std::string& data ) const
-   {
-      std::get< gen::template outer< I > >( m_tuple ).template element< gen::template inner< I > >( data );
-   }
-
    template< std::size_t I >
    void copy_to( std::string& data ) const
    {
diff --git a/include/tao/pq/result_traits_array.hpp b/include/tao/pq/result_traits_array.hpp
index c98c8b5..aac03f3 100644
--- a/include/tao/pq/result_traits_array.hpp
+++ b/include/tao/pq/result_traits_array.hpp
@@ -48,7 +48,7 @@ namespace tao::pq
       [[nodiscard]] auto parse_unquoted( const char*& value ) -> std::string;
 
       template< typename T >
-         requires( !pq::is_array_result< T > ) && ( result_traits_size< T > == 1 )
+         requires( !pq::is_array_result< T > )
       [[nodiscard]] auto parse( const char*& value ) -> T
       {
          if( *value == '"' ) {
@@ -104,10 +104,12 @@ namespace tao::pq
          }
       }
 
+      template< typename T >
+      concept array_result_type = ( pq::is_array_result< T > && ( pq::is_array_result< typename T::value_type > || ( result_traits_size< typename T::value_type > == 1 ) ) );
+
    }  // namespace internal
 
-   template< typename T >
-      requires is_array_result< T >
+   template< internal::array_result_type T >
    struct result_traits< T >
    {
       static auto from( const char* value ) -> T