From a6467772f4a8800c72ea1880b283c7b3555d28ef Mon Sep 17 00:00:00 2001
From: ADAM David Alan Martin <adam@recursive.engineer>
Date: Thu, 4 Apr 2024 15:41:27 -0400
Subject: [PATCH] Make it possible to use arbitrary code in making delimited
 lists.

---
 delimited_list.cc        | 14 +++++++-------
 delimited_list.h         | 13 +++++++++++--
 delimited_list.test/0.cc | 30 ++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+), 9 deletions(-)

diff --git a/delimited_list.cc b/delimited_list.cc
index a4ebf9b..14ded6e 100644
--- a/delimited_list.cc
+++ b/delimited_list.cc
@@ -28,23 +28,23 @@ namespace Alepha::Hydrogen  ::detail::  delimited_list_m
 		: virtual public IOStreams::StackableStreambuf, virtual public std::streambuf
 	{
 		private:
-			std::string delim;
+			DelimiterWriter writer;
 			bool first= true;
 
 		public:
 			explicit
-			DelimitedListStreambuf( std::ios &is, const std::string delim )
-				: StackableStreambuf( is ), delim( delim )
+			DelimitedListStreambuf( std::ios &is, const DelimiterWriter writer )
+				: StackableStreambuf( is ), writer( writer )
 			{
 				tracker.get( is )= this;
 				if( C::debug ) error() << "Streambuf adapted." << std::endl;
 			}
 
 			void
-			doNext()
+			doNext( std::ostream &out )
 			{
 				if( C::debug ) error() << "Do Next called" << std::endl;
-				if( not first ) out() << delim;
+				if( not first ) writer( out );
 				first= false;
 			}
 
@@ -66,7 +66,7 @@ namespace Alepha::Hydrogen  ::detail::  delimited_list_m
 	{
 		if( C::debug ) error() << "Marker called" << std::endl;
 		auto thisTracker= tracker.get( os );
-		if( thisTracker != nullptr ) thisTracker->doNext();
+		if( thisTracker != nullptr ) thisTracker->doNext( os );
 
 		return os;
 	}
@@ -74,6 +74,6 @@ namespace Alepha::Hydrogen  ::detail::  delimited_list_m
 	void
 	impl::build_streambuf( std::ostream &os, StartDelimitedList &&params )
 	{
-		new impl_cc::DelimitedListStreambuf( os, params.delimiter );
+		new impl_cc::DelimitedListStreambuf( os, params.writer );
 	}
 }
diff --git a/delimited_list.h b/delimited_list.h
index 27239f9..a89fe80 100644
--- a/delimited_list.h
+++ b/delimited_list.h
@@ -12,11 +12,20 @@ namespace Alepha::Hydrogen  ::detail::  delimited_list_m
 {
 	inline namespace exports {}
 
+	using DelimiterWriter= std::function< void ( std::ostream & ) >;
 	struct DelimitedList_params
 	{
-		const std::string delimiter;
+		DelimiterWriter writer;
 
-		explicit DelimitedList_params( const std::string delimiter ) : delimiter( delimiter ) {}
+		explicit
+		DelimitedList_params( const std::string delimiter )
+			: writer( [delimiter] ( std::ostream &os ) { os << delimiter; } )
+		{}
+
+		explicit
+		DelimitedList_params( DelimiterWriter writer )
+			: writer( writer )
+		{}
 	};
 
 	struct MarkItem_t {};
diff --git a/delimited_list.test/0.cc b/delimited_list.test/0.cc
index a671af8..5af3f47 100644
--- a/delimited_list.test/0.cc
+++ b/delimited_list.test/0.cc
@@ -7,6 +7,8 @@ static_assert( __cplusplus > 2020'99 );
 
 #include <Alepha/Utility/evaluation_helpers.h>
 
+#include <Alepha/IOStreams/delimiters.h>
+
 static auto init= Alepha::Utility::enroll <=[]
 {
 	using namespace Alepha::Testing::literals;
@@ -32,4 +34,32 @@ static auto init= Alepha::Utility::enroll <=[]
 	{
 		{ "Simple", { { "Alpha", "Bravo", "Charlie", "Delta", "Echo" } }, "Alpha, Bravo, Charlie, Delta, Echo" },
 	};
+
+	"Simple Comma Testing using delim function"_test <=TableTest
+	<
+		[]( std::vector< std::string > names )
+		{
+			std::ostringstream oss;
+			oss << setDelimiter( Alepha::IOStreams::fieldDelimiter, ", " );
+
+			oss << Alepha::StartDelimitedList
+			{
+				[]( std::ostream &os )
+				{
+					os << Alepha::IOStreams::fieldDelimiter;
+				}
+			};
+
+			for( const auto &name: names )
+			{
+				oss << Alepha::NextItem << name;
+			}
+
+			return oss.str();
+		}
+	>
+	::Cases
+	{
+		{ "Simple", { { "Alpha", "Bravo", "Charlie", "Delta", "Echo" } }, "Alpha, Bravo, Charlie, Delta, Echo" },
+	};
 };