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

#pragma once
#include "asset/Asset.hpp"
#include "display/shader/ShaderManager.hpp"
#include "scene/debug/SceneDebugLine.hpp"
#include "physics/ScenePhysicsManager.hpp"
#include "state/StateEvent.hpp"
#include "state/StateOwner.hpp"

namespace Dawn {
  class DawnGame;
  class RenderPipeline;
  class SceneItem;
  class SceneItemComponent;

  typedef int32_t sceneitemid_t;

  template<class T>
  std::shared_ptr<T> _sceneForwardGetComponent(std::shared_ptr<SceneItem> item);

  template<class T>
  std::vector<std::shared_ptr<T>> _sceneForwardGetComponents(
    std::shared_ptr<SceneItem> item
  );

  class Scene : public StateOwner, public std::enable_shared_from_this<Scene> {
    private:
      sceneitemid_t nextId;
      std::map<sceneitemid_t, std::shared_ptr<SceneItem>> items;
      std::map<sceneitemid_t, std::shared_ptr<SceneItem>> itemsNotInitialized;
    
    public:
      std::weak_ptr<DawnGame> game;
      ScenePhysicsManager *physics;
      StateEvent<float_t> eventSceneUpdate;
      StateEvent<float_t> eventSceneUnpausedUpdate;

      /**
       * Construct a new Scene instance.
       * 
       * @param game Reference to the game that this scene belongs to.
       */
      Scene(std::weak_ptr<DawnGame> game);

      /**
       * Perform a one frame synchronous tick on the current scene. This may
       * change in future to be more event-like.
       */
      void update();

      /**
       * Create a Scene Item object and add to the current scene.
       * 
       * @return A shared pointer to the created SceneItem.
       */
      template<class T>
      std::shared_ptr<T> createSceneItemOfType() {
        sceneitemid_t id = this->nextId++;
        auto item = std::make_shared<T>(weak_from_this(), id);
        assertNotNull(item, "Failed to create SceneItem (Memory Filled?)");
        this->itemsNotInitialized[id] = item;
        return item;
      }

      /**
       * Create a Scene Item object and add to the current scene.
       * 
       * @return A shared pointer to the created SceneItem.
       */
      std::shared_ptr<SceneItem> createSceneItem();

      /**
       * Returns the required assets for this scene. Assets required are meant
       * to be referenced back to the loader so that special loading actions can
       * be performed against them.
       * 
       * @return List of assets required by this scene.
       */
      virtual std::vector<std::shared_ptr<Asset>> getRequiredAssets() = 0;

      /**
       * Method to begin the actual staging of the scene, typically called after
       * the scene has finished loading.
       */
      virtual void stage() = 0;

      /**
       * Finds an existing component on the scene (Root Level Only) that has a
       * component matching the given component type. Returns nullptr if no item
       * with the specified component could be found.
       * 
       * @tparam Component type to look for.
       * @return Pointer to the found component (and by extension the item).
       */
      template<class T>
      std::shared_ptr<T> findComponent() {
        auto it = this->itemsNotInitialized.begin();
        while(it != this->itemsNotInitialized.end()) {
          auto component = _sceneForwardGetComponent<T>(it->second);
          if(component != nullptr) return component;
          ++it;
        }
        auto it2 = this->items.begin();
        while(it2 != this->items.end()) {
          auto component = _sceneForwardGetComponent<T>(it2->second);
          if(component != nullptr) return component;
          ++it2;
        }
        return nullptr;
      }

      /**
       * Finds all exisitng components on the scene (Root Level Only) that has a
       * matching component of the given component type.
       * 
       * @tparam Component type to look for.
       * @return List of matching compnoents.
       */
      template<class T>
      std::vector<std::shared_ptr<T>> findComponents() {
        std::vector<std::shared_ptr<T>> components;

        auto it = this->itemsNotInitialized.begin();
        while(it != this->itemsNotInitialized.end()) {
          auto component = _sceneForwardGetComponent<T>(it->second);
          if(component != nullptr) components.push_back(component);
          ++it;
        }

        auto it2 = this->items.begin();
        while(it2 != this->items.end()) {
          auto component = _sceneForwardGetComponent<T>(it2->second);
          if(component != nullptr) components.push_back(component);
          ++it2;
        }
        return components;
      }
      /**
       * Destroys a previously initialized Scene.
       */
      ~Scene();

      friend class RenderPipeline;
  };
}