// Copyright (c) 2022 Dominic Masters
// 
// This software is released under the MIT License.
// https://opensource.org/licenses/MIT

#pragma once
#include "scene/SceneItemComponent.hpp"
#include "display/RenderTarget.hpp"
#include "scene/components/display/Camera.hpp"

namespace Dawn {
  enum UIDrawType {
    UI_DRAW_TYPE_WORLD_ABSOLUTE,
    UI_DRAW_TYPE_WORLD_CAMERA_RELATIVE,
    UI_DRAW_TYPE_CAMERA_OVERLAY
  };

  class UIComponent;
  struct UIMenu;

  class UICanvas : public SceneItemComponent {
    protected:
      Camera *camera = nullptr;
      struct UIMenu *currentMenu = nullptr;

      void onRenderTargetResize(float_t w, float_t h);
      void onSceneUpdate();

    public:
      /**
       * Creates a UI Canvas Scene Item Element, and attaches it to the provided
       * scene.
       * 
       * @param scene Scene to create the UI Canvas for.
       * @return Created UI Canvas.
       */
      static UICanvas * create(Scene *scene);

      //======================================================================//
      std::vector<UIComponent*> children;
      UIDrawType drawType = UI_DRAW_TYPE_WORLD_CAMERA_RELATIVE;

      /**
       * Constructs the UI Canvas Scene Item Component.
       * 
       * @param item Item that this canvas item belongs to.
       */
      UICanvas(SceneItem *item);

      /**
       * Sets the camera used by the UI canvas.
       * 
       * @param camera Camera to set for the UI canvas.
       */
      void setCamera(Camera *camera);

      /**
       * Construct and append a UI item to this UI Canvas.
       * 
       * @tparam Type of the UI Item.
       * @return Pointer to the created UI Item.
       */
      template<class T>
      T * addElement() {
        auto item = new T(this);
        this->children.push_back(item);
        return item;
      }

      /**
       * Find a UI Element attached to this canvas.
       * 
       * @tparam Type of the UI item to find.
       * @return Pointer to first matching element of type T.
       */
      template<class T>
      T * findElement() {
        auto it = this->children.begin();
        while(it != this->children.end()) {
          auto castedAs = dynamic_cast<T*>(*it);
          if(castedAs != nullptr) return castedAs;
          ++it;
        }
        return nullptr;
      }
      
      /**
       * Returns the width of the root UI Canvas size. In future I may allow 
       * this to be dynamic, right now it uses the render canvas however.
       * 
       * @return Width of the UI Canvas.
       */
      float_t getWidth();

      /**
       * Returns the height of this UI Canvas element.
       * 
       * @return Height of the UI Canvas.
       */
      float_t getHeight();

      /**
       * Returns the currently active menu for this UI Canvas.
       * 
       * @return The currently active menu, or nullptr if there is none.
       */
      struct UIMenu * getCurrentMenu();

      /**
       * Sets the currently active menu, and ticks it appropriately.
       * 
       * @param menu Menu to set as the current active menu.
       */
      void setCurrentMenu(struct UIMenu *menu);

      void onStart() override;
      void onDispose() override;
  };
}