Line data    Source code

       1              : #pragma once
       2              : 
       3              : #include <functional>
       4              : 
       5              : namespace Amplitron {
       6              : 
       7              : /**
       8              :  * @brief Sentinel type for components that have no local render state.
       9              :  *
      10              :  * Used as the default State parameter in UIComponent so that components
      11              :  * without internal state don't carry a useless `int state_` member.
      12              :  */
      13              : struct EmptyState {};
      14              : 
      15              : /**
      16              :  * @brief Base template class for all reactive UI components.
      17              :  *
      18              :  * Enforces a React-like component structure:
      19              :  * - Props: Immutable configuration/data passed from the parent GuiManager
      20              :  *          every frame before render() is called.
      21              :  * - State: Local, mutable state owned by the component (e.g., animation
      22              :  *          timers, transient open/close flags). Defaults to EmptyState for
      23              :  *          components that need no persistent local state.
      24              :  *
      25              :  * Contract:
      26              :  *   1. Parent calls set_props(p) to push new data into the component.
      27              :  *   2. Parent calls render() — the component only reads props_ and state_.
      28              :  *   3. Mutations are communicated back through callbacks stored in Props,
      29              :  *      NOT by letting the component reach into the engine directly.
      30              :  */
      31              : template <typename Props, typename State = EmptyState>
      32           29 : class UIComponent {
      33              : public:
      34          107 :     virtual ~UIComponent() = default;
      35              : 
      36              :     /** @brief Push new props (inputs) into the component before render(). */
      37           30 :     virtual void set_props(const Props& new_props) {
      38           30 :         props_ = new_props;
      39           30 :     }
      40              : 
      41              :     /**
      42              :      * @brief Render the component using current props_ and state_.
      43              :      * Must be implemented by every concrete component.
      44              :      */
      45              :     virtual void render() = 0;
      46              : 
      47              :     /** @brief Read the current local state. */
      48              :     const State& get_state() const { return state_; }
      49              : 
      50              :     /**
      51              :      * @brief React-style setState: replace local state and trigger the
      52              :      * optional on_state_change() hook.
      53              :      */
      54            6 :     void set_state(const State& new_state) {
      55            6 :         state_ = new_state;
      56            6 :         on_state_change();
      57            6 :     }
      58              : 
      59              :     /**
      60              :      * @brief Functional setState: apply an updater lambda to a copy of the
      61              :      * current state, then commit and notify.
      62              :      */
      63            6 :     void set_state(std::function<void(State&)> updater) {
      64            6 :         State next = state_;
      65            6 :         updater(next);
      66            6 :         set_state(next);
      67            6 :     }
      68              : 
      69              : protected:
      70              :     Props props_;
      71              :     State state_;
      72              : 
      73              :     /** @brief Optional hook called after state has been updated. */
      74            6 :     virtual void on_state_change() {}
      75              : };
      76              : 
      77              : } // namespace Amplitron