From 66e8acfd5b6d65770bfdb1ccb26a4cd08f14136a Mon Sep 17 00:00:00 2001
From: ADAM David Alan Martin <adam@recursive.engineer>
Date: Wed, 3 Apr 2024 15:53:43 -0400
Subject: [PATCH] List delimiting primitive for output streams.

---
 CMakeLists.txt                     |  2 +
 delimited_list.cc                  | 79 ++++++++++++++++++++++++++++++
 delimited_list.h                   | 42 ++++++++++++++++
 delimited_list.test/0.cc           | 35 +++++++++++++
 delimited_list.test/CMakeLists.txt |  1 +
 5 files changed, 159 insertions(+)
 create mode 100644 delimited_list.cc
 create mode 100644 delimited_list.h
 create mode 100644 delimited_list.test/0.cc
 create mode 100644 delimited_list.test/CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 77b9477..83127ec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -14,6 +14,7 @@ add_library( alepha SHARED
 	string_algorithms.cc
 	word_wrap.cc
 	Thread.cc
+	delimited_list.cc
 )
 # Everything else depends upon it
 link_libraries( alepha )
@@ -40,6 +41,7 @@ add_subdirectory( assertion.test )
 add_subdirectory( Constness.test )
 add_subdirectory( Blob.test )
 add_subdirectory( Capabilities.test )
+add_subdirectory( delimited_list.test )
 
 # Sample applications
 add_executable( example example.cc )
diff --git a/delimited_list.cc b/delimited_list.cc
new file mode 100644
index 0000000..a4ebf9b
--- /dev/null
+++ b/delimited_list.cc
@@ -0,0 +1,79 @@
+static_assert( __cplusplus > 2020'99 );
+
+#include "delimited_list.h"
+
+#include <Alepha/error.h>
+
+#include <Alepha/IOStreams/StreamState.h>
+
+namespace Alepha::Hydrogen  ::detail::  delimited_list_m
+{
+
+	namespace
+	{
+		namespace C
+		{
+			const bool debug= false;
+		}
+
+		namespace impl_cc
+		{
+			struct DelimitedListStreambuf;
+		}
+
+		IOStreams::StreamState< impl_cc::DelimitedListStreambuf * > tracker{ [] { return nullptr; } };
+	}
+
+	struct impl_cc::DelimitedListStreambuf
+		: virtual public IOStreams::StackableStreambuf, virtual public std::streambuf
+	{
+		private:
+			std::string delim;
+			bool first= true;
+
+		public:
+			explicit
+			DelimitedListStreambuf( std::ios &is, const std::string delim )
+				: StackableStreambuf( is ), delim( delim )
+			{
+				tracker.get( is )= this;
+				if( C::debug ) error() << "Streambuf adapted." << std::endl;
+			}
+
+			void
+			doNext()
+			{
+				if( C::debug ) error() << "Do Next called" << std::endl;
+				if( not first ) out() << delim;
+				first= false;
+			}
+
+		private:
+			void writeChar( char ) override { throw "Unimpl"; }
+			void drain() override { throw "Unimpl"; }
+
+			int
+			overflow( const int ch ) override
+			{
+				if( C::debug ) error() << "Overflow called" << std::endl;
+				return forwardOverflow( ch );
+			}
+	};
+
+
+	std::ostream &
+	impl::operator << ( std::ostream &os, MarkItem_t )
+	{
+		if( C::debug ) error() << "Marker called" << std::endl;
+		auto thisTracker= tracker.get( os );
+		if( thisTracker != nullptr ) thisTracker->doNext();
+
+		return os;
+	}
+
+	void
+	impl::build_streambuf( std::ostream &os, StartDelimitedList &&params )
+	{
+		new impl_cc::DelimitedListStreambuf( os, params.delimiter );
+	}
+}
diff --git a/delimited_list.h b/delimited_list.h
new file mode 100644
index 0000000..27239f9
--- /dev/null
+++ b/delimited_list.h
@@ -0,0 +1,42 @@
+static_assert( __cplusplus > 2020'99 );
+
+#pragma once
+
+#include <Alepha/Alepha.h>
+
+#include <ostream>
+
+#include <Alepha/IOStreams/StackableStreambuf.h>
+
+namespace Alepha::Hydrogen  ::detail::  delimited_list_m
+{
+	inline namespace exports {}
+
+	struct DelimitedList_params
+	{
+		const std::string delimiter;
+
+		explicit DelimitedList_params( const std::string delimiter ) : delimiter( delimiter ) {}
+	};
+
+	struct MarkItem_t {};
+
+	namespace exports
+	{
+		constexpr MarkItem_t NextItem;;
+
+		using StartDelimitedList= IOStreams::PushStack< DelimitedList_params >;
+		constexpr IOStreams::PopStack EndDelimitedList;
+	}
+
+	inline namespace impl
+	{
+		void build_streambuf( std::ostream &, StartDelimitedList && );
+		std::ostream &operator << ( std::ostream &os, MarkItem_t ); 
+	}
+}
+
+namespace Alepha::Hydrogen::inline exports::inline delimited_list_m
+{
+	using namespace detail::delimited_list_m::exports;
+}
diff --git a/delimited_list.test/0.cc b/delimited_list.test/0.cc
new file mode 100644
index 0000000..a671af8
--- /dev/null
+++ b/delimited_list.test/0.cc
@@ -0,0 +1,35 @@
+static_assert( __cplusplus > 2020'99 );
+
+#include "../delimited_list.h"
+
+#include <Alepha/Testing/test.h>
+#include <Alepha/Testing/TableTest.h>
+
+#include <Alepha/Utility/evaluation_helpers.h>
+
+static auto init= Alepha::Utility::enroll <=[]
+{
+	using namespace Alepha::Testing::literals;
+	using namespace std::literals::string_literals;
+
+	using namespace Alepha::Testing::exports;
+
+	"Simple Comma Testing"_test <=TableTest
+	<
+		[]( std::vector< std::string > names )
+		{
+			std::ostringstream oss;
+			oss << Alepha::StartDelimitedList{ ", "s };
+			for( const auto &name: names )
+			{
+				oss << Alepha::NextItem << name;
+			}
+
+			return oss.str();
+		}
+	>
+	::Cases
+	{
+		{ "Simple", { { "Alpha", "Bravo", "Charlie", "Delta", "Echo" } }, "Alpha, Bravo, Charlie, Delta, Echo" },
+	};
+};
diff --git a/delimited_list.test/CMakeLists.txt b/delimited_list.test/CMakeLists.txt
new file mode 100644
index 0000000..b099603
--- /dev/null
+++ b/delimited_list.test/CMakeLists.txt
@@ -0,0 +1 @@
+unit_test( 0 )