Initial import

main.cpp

@@ -0,0 +1,114 @@
+#include <iostream>
+#include <string>
+#include <list>
+#include <functional>
+#include <tuple>
+#include <variant>
+#include <thread>
+#include <sstream>
+
+using namespace std::chrono_literals;
+
+template <typename Message> struct ConsoleIO {
+  static auto ReadlineS(std::istream& is, std::function<Message(std::string)> f) {
+    return [=,&is] {
+      std::string line;
+      std::getline(is, line);
+      return f(line);
+    };
+  }
+
+  static std::function<Message()>
+  Readline(std::function<Message(std::string)> f) {
+    return ReadlineS (std::ref(std::cin), f);
+  }
+
+  static std::function<Message()>
+  Prompt(std::string prompt, std::function<Message(std::string)> f) {
+    return [=] {
+      std::cout << prompt << std::flush;
+      return Readline (f)();
+    };
+  }
+};
+
+template <typename ModelT, typename MessageT> struct AppT {
+  using Model = ModelT;
+  using Message = MessageT;
+  using Command = std::function<Message()>;
+  using InitResult = std::tuple<Model, std::list<Command>>;
+  using UpdateResult = InitResult;
+  using ViewResult = std::string;
+  using ReadLine = std::function<Message (std::string)>;
+  using Console = ConsoleIO<Message>;
+
+  using Init = std::function<InitResult ()>;
+  using Update = std::function<UpdateResult (Model, const Message&)>;
+  using View = std::function<ViewResult (const Model&)>;
+  using Done = std::function<bool (const Model&)>;
+
+  struct Config {
+    Init init;
+    Update update;
+    View view;
+    Done done;
+  };
+
+  int run (const Config & cfg) {
+    auto const& [init, update, view, done] = cfg;
+    auto [state, cmds] = init();
+
+    while (! done (state)) {
+      std::cout << view(state) << "\n";
+
+      if (!cmds.empty()) {
+        auto [newstate, newcmds] = update (state, cmds.front()());
+        cmds.erase (cmds.begin());
+        cmds.insert (cmds.end(), std::begin(newcmds), std::end (newcmds));
+
+        state = newstate;
+      }
+      std::this_thread::sleep_for (100ms);
+    }
+
+    std::cout << "app finished with " << cmds.size() << " pending commands and final state: \n" << view(state) << '\n';
+
+    return 0;
+  }
+};
+
+// user defined
+
+using Model = int;
+
+struct SetState {
+  Model s;
+};
+
+using Message = std::variant<SetState>;
+
+auto strToState (const std::string& s) -> Message {
+  std::stringstream sstr(s);
+  int r;
+  sstr >> r;
+  return SetState { r };
+ }
+
+int main() {
+  using App = AppT<int, Message>;
+  App app;
+  return app.run(App::Config{
+      []() -> App::InitResult {
+        return {23, {App::Console::Prompt("> ", strToState)}};
+      }, // init
+      [](const App::Model &state,
+         const App::Message &msg) -> App::UpdateResult {
+        return {std::get<SetState>(msg).s,
+                {App::Console::Prompt("> ", strToState)}};
+      }, // update
+      [](const App::Model &state) -> App::ViewResult {
+        return "Model " + std::to_string(state);
+      },                                                          // view
+      [](const App::Model &state) -> bool { return state == 42; } // done
+  });
+}