/************************************************************************************//*!
\file           ECS.hxx
\author         Tng Kah Wei, kahwei.tng, 390009620
\par            email: kahwei.tng\@digipen.edu
\date           Oct 28, 2021
\brief          Contains the definitions of the GameObject managed class which define an
                abstraction for working with Entities in managed code.
                
                Note: This file is written in C++17/CLI.
 
Copyright (C) 2021 DigiPen Institute of Technology.
Reproduction or disclosure of this file or its contents without the prior written consent 
of DigiPen Institute of Technology is prohibited.
*//*************************************************************************************/
#pragma once

// External Dependencies
#include "Engine/ECS_Base/System/SHComponentManager.h"
// Project Includes
#include "Components/Component.hxx"

namespace SHADE
{
    /// <summary>
    /// Static class which contains functions that map Pls::ECS's Component manipulation
    /// functions to managed generic functions.
    /// </summary>
    private ref class ECS abstract sealed
    {
      public:
        /*-----------------------------------------------------------------------------*/
        /* Component Manipulation Functions                                            */
        /*-----------------------------------------------------------------------------*/
        /// <summary>
        /// Adds a Component to the specified Entity.
        /// </summary>
        /// <typeparam name="T">Type of the Component to add.</typeparam>
        /// <param name="entity">
        /// Entity object that should have the specified Component added to.
        /// </param>
        /// <returns>Reference to the Component that was added.</returns>
        generic<typename T> where T : BaseComponent
        static T AddComponent(EntityID entity);
        /// <summary>
        /// Gets a Component from the specified Entity.
        /// </summary>
        /// <typeparam name="T">Type of the Component to get.</typeparam>
        /// <param name="entity"> Entity object to get the Component from. </param>
        /// <returns>
        /// Reference to the Component or null if the Entity does not have the
        /// specified Component.
        /// </returns>
        generic<typename T> where T : BaseComponent
        static T GetComponent(EntityID entity);
        /// <summary>
        /// Retrieves the first Component from the specified GameObjectt's children that
        /// matches the specified type.
        /// </summary>
        /// <typeparam name="T">Type of the Component to get.</typeparam>
        /// <param name="entity"> Entity object to get the Component from. </param>
        /// <returns>
        /// Reference to the Component or null if the Entity does not have the
        /// specified Component.
        /// </returns>
        generic<typename T> where T : BaseComponent
        static T GetComponentInChildren(EntityID entity);
        /// <summary>
        /// Ensures a Component on the specified Entity.
        /// </summary>
        /// <typeparam name="T">Type of the Component to ensure.</typeparam>
        /// <param name="entity"> Entity object to ensure the Component on. </param>
        /// <returns>Reference to the Component.</returns>
        generic<typename T> where T : BaseComponent
        static T EnsureComponent(EntityID entity);
        /// <summary>
        /// Checks if the specified Entity has the specified Component.
        /// </summary>
        /// <typeparam name="T">Type of the Component to check for.</typeparam>
        /// <param name="entity">Entity object to check for the Component.</param>
        /// <returns>
        /// True if the specified Entity has the specified Component. False otherwise.
        /// </returns>
        generic<typename T> where T : BaseComponent
        static bool HasComponent(EntityID entity);
        /// <summary>
        /// Removes a Component from the specified Entity.
        /// </summary>
        /// <typeparam name="T">Type of the Component to remove.</typeparam>
        /// <param name="entity">
        /// Entity object that should have the specified Component removed from/
        /// </param>
        generic<typename T> where T : BaseComponent
        static void RemoveComponent(EntityID entity);

      internal:
        /*-----------------------------------------------------------------------------*/
        /* Type Definitions                                                            */
        /*-----------------------------------------------------------------------------*/
        /// <summary>
        /// Pointer to a function for Component manipulation operations.
        /// </summary>
        using ComponentFunc = void(*)(const EntityID&);
        using ComponentHasFunc = bool(*)(const EntityID&);
        /// <summary>
        /// Contains a set of Component related data used for resolving operations for
        /// each Component.
        /// </summary>
        value struct ComponentSet
        {
          public:
            System::Type^ Type;
            ComponentFunc    AddFunction;
            ComponentHasFunc HasFunction;
            ComponentFunc    RemoveFunction;

        };

        /*-----------------------------------------------------------------------------*/
        /* Static Functions                                                            */
        /*-----------------------------------------------------------------------------*/
        /// <summary>
        /// Retrieves a pointer to the native unmanaged component of the specified 
        /// Entity.
        /// </summary>
        /// <returns>
        /// Pointer to the native component. Will be nullptr if it does not exist.
        /// </returns>
        /// <exception cref="System.InvalidOperationException">
        /// Thrown if the Entity specified is invalid.
        /// </exception>
        /// <exception cref="System.NullReferenceException">
        /// Thrown if an attempt to retrieve the native component fails.
        /// </exception>
        template<typename NativeComponent>
        static NativeComponent* GetNativeComponent(Entity entity);

      private:
        /*-----------------------------------------------------------------------------*/
        /* Constructors                                                                */
        /*-----------------------------------------------------------------------------*/
        /// <summary>
        /// Static constructor to initialize static data
        /// </summary>
        static ECS();

        /*-----------------------------------------------------------------------------*/
        /* Static Data Members                                                         */
        /*-----------------------------------------------------------------------------*/
        static System::Collections::Generic::List<ComponentSet> componentMap;

        /*-----------------------------------------------------------------------------*/
        /* Helper Functions                                                            */
        /*-----------------------------------------------------------------------------*/
        /// <summary>
        /// Creates a ComponentSet for a pair of Native and Managed Components.
        /// </summary>
        /// <typeparam name="NativeType">Type of the Native Component.</typeparam>
        /// <typeparam name="ManagedType">Type of the Managed Component.</typeparam>
        /// <returns>ComponentSet for the parameters specified.</returns>
        template<typename NativeType, typename ManagedType>
        static ComponentSet createComponentSet();
        /// <summary>
        /// Creates an instance of the Managed representation of a Component with a
        /// native Entity.
        /// </summary>
        /// <typeparam name="T">Type of Component to create.</typeparam>
        /// <param name="entity">Native Entity that this Component is tied to.</param>
        /// <returns>The created Managed representation of the Component.</returns>
        generic<typename T> where T : BaseComponent
        static T createManagedComponent(EntityID entity);
    };
}

#include "ECS.h++"