extract parser driver

lib/CMakeLists.txt

@@ -1,2 +1,3 @@
 add_library(aocpp src/Startup.cpp src/Coord.cpp src/Parsing.cpp)
-target_include_directories(aocpp PUBLIC include)
+target_include_directories(aocpp PUBLIC include)
+target_link_libraries(aocpp Boost::headers)

lib/include/aocpp/Parsing.hpp

@@ -2,12 +2,34 @@
 #define AOCPP_PARSING_HPP_
 
 #include <string>
+#include <iostream>
+#include <iterator>
 #include <vector>
 
+#include <boost/spirit/home/qi.hpp>
+
 namespace aocpp {
 
 auto SplitOn(std::string const& stuff, std::string const& sep) -> std::vector<std::string>;
 
+/// Parse the complete input stream according to the rules defined in 'Grammar'.
+/// Throws: std::runtime_error on failed parse
+template <typename G>
+auto ParseGrammar(G const& grammar, std::istream & in) -> typename G::start_type::attr_type
+{
+  namespace qi = boost::spirit::qi;
+  auto result = typename G::start_type::attr_type {};
+  auto const content = std::string{std::istreambuf_iterator{in}, {}};
+  auto b = content.begin(); // updated on successful parse
+  auto const e = content.end();
+
+  if (!qi::parse(b, e, grammar, result) || b != e) {
+    throw std::runtime_error{"Bad input file: " + content};
+  }
+
+  return result;
+}
+
 }
 
 #endif