Stop the application on EOF

main.cpp

@@ -6,25 +6,28 @@
 #include <variant>
 #include <thread>
 #include <sstream>
+#include <optional>
 
 using namespace std::chrono_literals;
 
 template <typename Message> struct ConsoleIO {
-  static auto ReadlineS(std::istream& is, std::function<Message(std::string)> f) {
+  static auto ReadlineS(std::istream& is, std::function<Message(std::optional<std::string>)> f) {
     return [=,&is] {
-      std::string line;
-      std::getline(is, line);
-      return f(line);
+      if (std::string line; std::getline(is, line)) {
+        return f(std::make_optional(line));
+      } else {
+        return f(std::nullopt);
+      }
     };
   }
 
   static std::function<Message()>
-  Readline(std::function<Message(std::string)> f) {
+  Readline(std::function<Message(std::optional<std::string>)> f) {
     return ReadlineS (std::ref(std::cin), f);
   }
 
   static std::function<Message()>
-  Prompt(std::string prompt, std::function<Message(std::string)> f) {
+  Prompt(std::string prompt, std::function<Message(std::optional<std::string>)> f) {
     return [=] {
       std::cout << prompt << std::flush;
       return Readline (f)();
@@ -79,36 +82,53 @@ template <typename ModelT, typename MessageT> struct AppT {
 
 // user defined
 
-using Model = int;
-
-struct SetState {
-  Model s;
+struct Model {
+bool done{false};
+  int value{0};
 };
 
-using Message = std::variant<SetState>;
+struct SetValue {
+  int s;
+};
 
-auto strToState (const std::string& s) -> Message {
-  std::stringstream sstr(s);
+struct Stop {
+};
+
+using Message = std::variant<SetValue, Stop>;
+
+auto userInputToMsg(const std::optional<std::string>& s) -> Message {
+
+  if (s) {
+    std::stringstream sstr(*s);
     int r;
     sstr >> r;
-  return SetState { r };
+    return SetValue { r };
+  } else {
+    return Stop{};
+  }
+
  }
 
 int main() {
-  using App = AppT<int, Message>;
+  using App = AppT<Model, Message>;
   App app;
   return app.run(App::Config{
       []() -> App::InitResult {
-        return {23, {App::Console::Prompt("> ", strToState)}};
+        return {{false, 23}, {App::Console::Prompt("> ", userInputToMsg)}};
       }, // init
-      [](const App::Model &state,
+      [](App::Model state,
          const App::Message &msg) -> App::UpdateResult {
-        return {std::get<SetState>(msg).s,
-                {App::Console::Prompt("> ", strToState)}};
+        if (auto stop = std::get_if<Stop>(&msg); stop) {
+          state.done = true;
+          return {state, {}};
+        } else {
+          state.value = std::get<SetValue>(msg).s;
+          return {state, {App::Console::Prompt("> ", userInputToMsg)}};
+        }
       }, // update
       [](const App::Model &state) -> App::ViewResult {
-        return "Model " + std::to_string(state);
+        return "Model " + std::to_string(state.value);
       },                                                          // view
-      [](const App::Model &state) -> bool { return state == 42; } // done
+      [](const App::Model &state) -> bool { return state.done; } // done
   });
 }