testbed: bare minimal input system

testbed/system/input_system.cpp

@@ -1,9 +1,20 @@
 #include <application/context.h>
+#include <component/input_listener_component.h>
 #include <entt/entity/registry.hpp>
 #include <system/input_system.h>
 
 namespace testbed {
 
+namespace internal {
+
+static void update_listeners(entt::registry &registry, input_listener_component::type command) {
+    for([[maybe_unused]] auto [entt, elem]: registry.view<input_listener_component>().each()) {
+        elem.command = command;
+    }
+}
+
+} // namespace internal
+
 void input_system(entt::registry &registry, const SDL_Event &event, bool &quit) {
     switch(event.type) {
     case SDL_EVENT_QUIT:
@@ -14,6 +25,18 @@ void input_system(entt::registry &registry, const SDL_Event &event, bool &quit)
         case SDLK_ESCAPE:
             quit = true;
             break;
+        case SDLK_UP:
+            internal::update_listeners(registry, input_listener_component::type::UP);
+            break;
+        case SDLK_DOWN:
+            internal::update_listeners(registry, input_listener_component::type::DOWN);
+            break;
+        case SDLK_LEFT:
+            internal::update_listeners(registry, input_listener_component::type::LEFT);
+            break;
+        case SDLK_RIGHT:
+            internal::update_listeners(registry, input_listener_component::type::RIGHT);
+            break;
         }
         break;
     }