module ecs.manager;

import std.experimental.allocator.mallocator : Mallocator;
import std.experimental.allocator;
import std.traits;

import ecs.system;
import ecs.entity;

alias gEM = EntityManager.instance;

class EntityManager
{

    static void initialize()
    {
        instance = Mallocator.instance.make!EntityManager;
    }

    void registerSystem(Sys)(int priority)
    {
        static void callUpdate(ref CallData data, void* entity)
        {
            static if(hasMember!(Sys,"update"))
            {
                Sys* s = cast(Sys*)data.system.system_pointer;
                s.update();
            }
        }
    
        System system;
        static if(hasMember!(Sys,"update"))
        {
            system.update = &callUpdate;
        }
        system.system_pointer = cast(void*)Mallocator.instance.make!Sys;

        if(systems is null)
        {
            systems = Mallocator.instance.makeArray!System(1);
            systems[0] = system;
        }
        else
        {
            Mallocator.instance.expandArray(systems,1);
            systems[$-1] = system;
        }
    }

    void registerComponent(Comp)()
    {
        uint size = Comp.sizeof;
        ComponentInfo info;
        info.size = size;
        info.aligment = 8;

        if(components is null)
        {
            components = Mallocator.instance.makeArray!ComponentInfo(1);
            components[0] = info;
        }
        else
        {
            Mallocator.instance.expandArray(components,1);
            components[$-1] = info;
        }
    }

    void update()
    {
        foreach(ref system;systems)
        {
            if(system.update is null)continue;
            CallData call_data = CallData(&system,null);
            system.update(call_data,null);
        }
    }

    EntityTemplate* allocateTemplate(uint[] components_ids)
    {
        uint size = 0;
        foreach(id;components_ids)
        {
            size += components[id].size;
        }

        size += EntityID.sizeof;

        ubyte[] entity_data = Mallocator.instance.makeArray!ubyte(size);
        EntityTemplate* temp = Mallocator.instance.make!EntityTemplate;
        temp.components = components_ids;
        temp.entity = cast(Entity*)entity_data.ptr;
        return temp;
    }

    struct CallData
    {
        System* system;
        uint[] deltas;
    }

    struct ComponentInfo 
    {
        int size;
	    int aligment;
    }

    System[] systems;
    ComponentInfo[] components;
    __gshared EntityManager instance;

}