From 7b42d5307a08f230f53a8524ea4f29cc3a9f6734 Mon Sep 17 00:00:00 2001
From: Jason Turner <jason@emptycrate.com>
Date: Tue, 28 Oct 2014 14:52:24 -0600
Subject: [PATCH] Add ability to register a user defined type conversion

Currently this adds a fair bit of overhead. It will need to be evaluated
further before it's merged.
---
 CMakeLists.txt                                |  2 +-
 include/chaiscript/dispatchkit/bootstrap.hpp  |  2 +-
 include/chaiscript/dispatchkit/boxed_cast.hpp |  4 +-
 .../chaiscript/dispatchkit/dispatchkit.hpp    |  2 +-
 .../dispatchkit/function_call_detail.hpp      |  2 +-
 ...st_conversion.hpp => type_conversions.hpp} | 43 ++++++++++++++++---
 .../chaiscript/language/chaiscript_engine.hpp |  9 +++-
 unittests/user_defined_conversions.chai       | 11 +++++
 8 files changed, 62 insertions(+), 13 deletions(-)
 rename include/chaiscript/dispatchkit/{dynamic_cast_conversion.hpp => type_conversions.hpp} (89%)
 create mode 100644 unittests/user_defined_conversions.chai

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c8ef4b9..720cb73 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -154,7 +154,7 @@ endif()
 include_directories(include)
 
 
-set(Chai_INCLUDES include/chaiscript/chaiscript.hpp include/chaiscript/chaiscript_threading.hpp include/chaiscript/dispatchkit/bad_boxed_cast.hpp include/chaiscript/dispatchkit/bind_first.hpp include/chaiscript/dispatchkit/bootstrap.hpp include/chaiscript/dispatchkit/bootstrap_stl.hpp include/chaiscript/dispatchkit/boxed_cast.hpp include/chaiscript/dispatchkit/boxed_cast_helper.hpp include/chaiscript/dispatchkit/boxed_number.hpp include/chaiscript/dispatchkit/boxed_value.hpp include/chaiscript/dispatchkit/dispatchkit.hpp include/chaiscript/dispatchkit/dynamic_cast_conversion.hpp include/chaiscript/dispatchkit/dynamic_object.hpp include/chaiscript/dispatchkit/exception_specification.hpp include/chaiscript/dispatchkit/function_call.hpp include/chaiscript/dispatchkit/function_call_detail.hpp include/chaiscript/dispatchkit/handle_return.hpp include/chaiscript/dispatchkit/operators.hpp include/chaiscript/dispatchkit/proxy_constructors.hpp include/chaiscript/dispatchkit/proxy_functions.hpp include/chaiscript/dispatchkit/proxy_functions_detail.hpp include/chaiscript/dispatchkit/register_function.hpp include/chaiscript/dispatchkit/type_info.hpp include/chaiscript/language/chaiscript_algebraic.hpp include/chaiscript/language/chaiscript_common.hpp include/chaiscript/language/chaiscript_engine.hpp include/chaiscript/language/chaiscript_eval.hpp include/chaiscript/language/chaiscript_parser.hpp include/chaiscript/language/chaiscript_prelude.chai include/chaiscript/language/chaiscript_prelude_docs.hpp include/chaiscript/utility/utility.hpp)
+set(Chai_INCLUDES include/chaiscript/chaiscript.hpp include/chaiscript/chaiscript_threading.hpp include/chaiscript/dispatchkit/bad_boxed_cast.hpp include/chaiscript/dispatchkit/bind_first.hpp include/chaiscript/dispatchkit/bootstrap.hpp include/chaiscript/dispatchkit/bootstrap_stl.hpp include/chaiscript/dispatchkit/boxed_cast.hpp include/chaiscript/dispatchkit/boxed_cast_helper.hpp include/chaiscript/dispatchkit/boxed_number.hpp include/chaiscript/dispatchkit/boxed_value.hpp include/chaiscript/dispatchkit/dispatchkit.hpp include/chaiscript/dispatchkit/type_conversions.hpp include/chaiscript/dispatchkit/dynamic_object.hpp include/chaiscript/dispatchkit/exception_specification.hpp include/chaiscript/dispatchkit/function_call.hpp include/chaiscript/dispatchkit/function_call_detail.hpp include/chaiscript/dispatchkit/handle_return.hpp include/chaiscript/dispatchkit/operators.hpp include/chaiscript/dispatchkit/proxy_constructors.hpp include/chaiscript/dispatchkit/proxy_functions.hpp include/chaiscript/dispatchkit/proxy_functions_detail.hpp include/chaiscript/dispatchkit/register_function.hpp include/chaiscript/dispatchkit/type_info.hpp include/chaiscript/language/chaiscript_algebraic.hpp include/chaiscript/language/chaiscript_common.hpp include/chaiscript/language/chaiscript_engine.hpp include/chaiscript/language/chaiscript_eval.hpp include/chaiscript/language/chaiscript_parser.hpp include/chaiscript/language/chaiscript_prelude.chai include/chaiscript/language/chaiscript_prelude_docs.hpp include/chaiscript/utility/utility.hpp)
 
 set_source_files_properties(${Chai_INCLUDES} PROPERTIES HEADER_FILE_ONLY TRUE)
 
diff --git a/include/chaiscript/dispatchkit/bootstrap.hpp b/include/chaiscript/dispatchkit/bootstrap.hpp
index c4fd18a..98648da 100644
--- a/include/chaiscript/dispatchkit/bootstrap.hpp
+++ b/include/chaiscript/dispatchkit/bootstrap.hpp
@@ -24,7 +24,7 @@
 #include "boxed_number.hpp"
 #include "boxed_value.hpp"
 #include "dispatchkit.hpp"
-#include "dynamic_cast_conversion.hpp"
+#include "type_conversions.hpp"
 #include "dynamic_object.hpp"
 #include "operators.hpp"
 #include "proxy_constructors.hpp"
diff --git a/include/chaiscript/dispatchkit/boxed_cast.hpp b/include/chaiscript/dispatchkit/boxed_cast.hpp
index b33d659..f2074d9 100644
--- a/include/chaiscript/dispatchkit/boxed_cast.hpp
+++ b/include/chaiscript/dispatchkit/boxed_cast.hpp
@@ -14,7 +14,7 @@
 #include "bad_boxed_cast.hpp"
 #include "boxed_cast_helper.hpp"
 #include "boxed_value.hpp"
-#include "dynamic_cast_conversion.hpp"
+#include "type_conversions.hpp"
 #include "type_info.hpp"
 
 namespace chaiscript {
@@ -86,7 +86,7 @@ namespace chaiscript
 #pragma warning(disable : 4127)
 #endif
 
-      if (std::is_polymorphic<typename detail::Bare_Type<Type>::type>::value && t_conversions)
+      if ( /*std::is_polymorphic<typename detail::Bare_Type<Type>::type>::value && */ t_conversions)
       {
         try {
           // std::cout << "trying an up conversion " << typeid(Type).name() << std::endl;
diff --git a/include/chaiscript/dispatchkit/dispatchkit.hpp b/include/chaiscript/dispatchkit/dispatchkit.hpp
index b8d4e19..910987e 100644
--- a/include/chaiscript/dispatchkit/dispatchkit.hpp
+++ b/include/chaiscript/dispatchkit/dispatchkit.hpp
@@ -27,7 +27,7 @@
 #include "boxed_cast.hpp"
 #include "boxed_cast_helper.hpp"
 #include "boxed_value.hpp"
-#include "dynamic_cast_conversion.hpp"
+#include "type_conversions.hpp"
 #include "dynamic_object.hpp"
 #include "proxy_constructors.hpp"
 #include "proxy_functions.hpp"
diff --git a/include/chaiscript/dispatchkit/function_call_detail.hpp b/include/chaiscript/dispatchkit/function_call_detail.hpp
index 2da9b7b..ee1d1bd 100644
--- a/include/chaiscript/dispatchkit/function_call_detail.hpp
+++ b/include/chaiscript/dispatchkit/function_call_detail.hpp
@@ -17,7 +17,7 @@
 #include "boxed_cast.hpp"
 #include "boxed_number.hpp"
 #include "boxed_value.hpp"
-#include "dynamic_cast_conversion.hpp"
+#include "type_conversions.hpp"
 #include "proxy_functions.hpp"
 
 namespace chaiscript
diff --git a/include/chaiscript/dispatchkit/dynamic_cast_conversion.hpp b/include/chaiscript/dispatchkit/type_conversions.hpp
similarity index 89%
rename from include/chaiscript/dispatchkit/dynamic_cast_conversion.hpp
rename to include/chaiscript/dispatchkit/type_conversions.hpp
index 9a90e7c..7036fe5 100644
--- a/include/chaiscript/dispatchkit/dynamic_cast_conversion.hpp
+++ b/include/chaiscript/dispatchkit/type_conversions.hpp
@@ -45,10 +45,7 @@ namespace chaiscript
 
         virtual ~bad_boxed_dynamic_cast() CHAISCRIPT_NOEXCEPT {}
     };
-  }
 
-  namespace exception
-  {
     class bad_boxed_type_cast : public bad_boxed_cast
     {
       public:
@@ -174,6 +171,32 @@ namespace chaiscript
           return Dynamic_Caster<Derived, Base>::cast(t_derived);
         }
     };
+
+
+    class Type_Conversion_Impl : public Type_Conversion_Base
+    {
+      public:
+        Type_Conversion_Impl(Type_Info t_from, Type_Info t_to, std::function<Boxed_Value (const Boxed_Value)> t_func)
+          : Type_Conversion_Base(std::move(t_to), std::move(t_from)),
+            m_func(std::move(t_func))
+        {
+        }
+
+        virtual Boxed_Value convert_down(const Boxed_Value &) const CHAISCRIPT_OVERRIDE
+        {
+          throw chaiscript::exception::bad_boxed_type_cast("No conversion exists");
+        }
+
+        virtual Boxed_Value convert(const Boxed_Value &t_from) const CHAISCRIPT_OVERRIDE
+        {
+          /// \todo better handling of errors from the conversion function
+          return m_func(t_from);
+        }
+
+      private:
+        std::function<Boxed_Value (const Boxed_Value)> m_func;
+    };
+
   }
 
   class Type_Conversions
@@ -191,6 +214,7 @@ namespace chaiscript
       void add_conversion(const std::shared_ptr<detail::Type_Conversion_Base> &conversion)
       {
         chaiscript::detail::threading::unique_lock<chaiscript::detail::threading::shared_mutex> l(m_mutex);
+        /// \todo error if a conversion already exists
         m_conversions.insert(conversion);
       }
 
@@ -240,8 +264,7 @@ namespace chaiscript
       {
         chaiscript::detail::threading::shared_lock<chaiscript::detail::threading::shared_mutex> l(m_mutex);
 
-        auto itr =
-          find(to, from);
+        auto itr = find(to, from);
 
         if (itr != m_conversions.end())
         {
@@ -283,7 +306,7 @@ namespace chaiscript
   /// Currently, due to limitations in module loading on Windows, and for the sake of portability,
   /// if you have a type that is introduced in a loadable module and is used by multiple modules
   /// (through a tertiary dll that is shared between the modules, static linking the new type
-  /// into both loadable modules would not be portable), you need to register the to type
+  /// into both loadable modules would not be portable), you need to register the type
   /// relationship in all modules that use the newly added type in a polymorphic way.
   ///
   /// Example:
@@ -309,6 +332,14 @@ namespace chaiscript
     return std::shared_ptr<detail::Type_Conversion_Base>(new detail::Dynamic_Conversion_Impl<Base, Derived>());
   }
 
+  namespace {
+    Type_Conversion type_conversion(const Type_Info &t_from, const Type_Info &t_to, 
+        const std::function<Boxed_Value (Boxed_Value)> &t_func)
+    {
+      return std::shared_ptr<detail::Type_Conversion_Base>(new detail::Type_Conversion_Impl(t_from, t_to, t_func));
+    }
+  }
+
 }
 
 
diff --git a/include/chaiscript/language/chaiscript_engine.hpp b/include/chaiscript/language/chaiscript_engine.hpp
index b476d29..95c4932 100644
--- a/include/chaiscript/language/chaiscript_engine.hpp
+++ b/include/chaiscript/language/chaiscript_engine.hpp
@@ -26,7 +26,7 @@
 #include "../dispatchkit/boxed_cast_helper.hpp"
 #include "../dispatchkit/boxed_value.hpp"
 #include "../dispatchkit/dispatchkit.hpp"
-#include "../dispatchkit/dynamic_cast_conversion.hpp"
+#include "../dispatchkit/type_conversions.hpp"
 #include "../dispatchkit/proxy_functions.hpp"
 #include "chaiscript_common.hpp"
 
@@ -353,6 +353,13 @@ namespace chaiscript
 
       m_engine.add(fun(&chaiscript::detail::Dispatch_Engine::get_type_name, std::ref(m_engine)), "name");
 
+      m_engine.add(fun(&chaiscript::detail::Dispatch_Engine::get_type, std::ref(m_engine)), "type");
+      m_engine.add(fun<void (const Type_Info &, const Type_Info &, const std::function<Boxed_Value (const Boxed_Value &)> &)> ( 
+            [=](const Type_Info &t_from, const Type_Info &t_to, const std::function<Boxed_Value (const Boxed_Value &)> &t_func) {
+              m_engine.add(chaiscript::type_conversion(t_from, t_to, t_func));
+            }
+          ), "add_type_conversion");
+              
 
       typedef std::string (ChaiScript::*load_mod_1)(const std::string&);
       typedef void (ChaiScript::*load_mod_2)(const std::string&, const std::string&);
diff --git a/unittests/user_defined_conversions.chai b/unittests/user_defined_conversions.chai
new file mode 100644
index 0000000..e73e92a
--- /dev/null
+++ b/unittests/user_defined_conversions.chai
@@ -0,0 +1,11 @@
+
+add_type_conversion(type("string"), type("Type_Info"), fun(s) { return type(s); });
+
+// This looks simple, but it takes the string "string" and using the registered
+// conversion above, automatically converts that into a Type_Info object, which then
+// allows the Type_Info.name() function to be called
+
+assert_equal("string".name(), "string");
+
+
+