ECS.h

#pragma once

#include <vector>
#include <string>

#include "Components.h"

#define MAX_ENTITIES 1024

template <typename ComponentType>
struct ComponentList
{
    std::vector<ComponentType> List;
    std::vector<int> Unused;
    std::vector<int> Map;
    COMP_MASKS Mask;
    int Count;

    ComponentList()
    {
        for (int i = 0; i < MAX_ENTITIES; i++)
            Map.push_back(0);
    }
};

class ECS
{
    public:
        ECS();
        ~ECS();

        //-- Entity Handling Methods --//
        int EntityCreate();
        void EntityDestroy(int EntityId);

        //-- Component handling methods --//
        template <typename CompType>
        CompType* EntityAddComponent(int EntityId, ComponentList<CompType> &Component);

        template <typename CompType>
        void EntityRemoveComponent(int EntityId, ComponentList<CompType> &Component);

        template <typename CompType>
        bool EntityHasComponent(int EntityId, ComponentList<CompType> Component);

        //-- Entity Masks --//
        std::vector<int64_t> Entities;
        std::vector<int> FreeEntitiesList;
        int EntitiesCount;

        //-- List of Component Lists --//
        std::vector<ComponentList<CompGeneric>*> ComponentLists;

        //-- Component Lists --//
        ComponentList<CompInfo>     InfoComps;     // Information Components
        ComponentList<CompPosition> PositionComps; // Position Components
        ComponentList<CompSpeed>    SpeedComps;    // Speed Components
        ComponentList<CompSprite>   SpriteComps;   // Sprite Components
};

//----------------------------------------------------
//----- Attach a component to an entity --------------
//----------------------------------------------------
template <typename CompType>
CompType* ECS::EntityAddComponent(int EntityId, ComponentList<CompType> &Component)
{
    Entities[EntityId] |= Component.Mask;

    if (Component.Unused.size() == 0)
    {
        CompType newComponent;
        Component.Map[EntityId] = Component.Count;
        Component.Count++;
        Component.List.push_back(newComponent);
        return &Component.List.back();            // Return pointer to added component for editing.
    }
    else
    {
        Component.Map[EntityId] = Component.Unused[Component.Unused.back()];
        Component.Unused.pop_back();
        return &Component.List[Component.Map[EntityId]]; // Return pointer to added component for editing.
    }
};

//----------------------------------------------------
//----- Remove a component from an entity ------------
//----------------------------------------------------
template <typename CompType>
void ECS::EntityRemoveComponent(int EntityId, ComponentList<CompType> &Component)
{
    Entities[EntityId] ^= Component.Mask;

    Component.Unused.push_back(Component.Map[EntityId]);
};

//----------------------------------------------------
//----- Check if an entity has a component -----------
//----------------------------------------------------
template <typename CompType>
bool ECS::EntityHasComponent(int EntityId, ComponentList<CompType> Component)
{
    return ((Entities[EntityId] & Component.Mask) == Component.Mask);
};