entity_system.h

/*
 * Copyright 2016 Ophidian
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
 */

#ifndef OPHIDIAN_SRC_ENTITY_SYSTEM_ENTITY_SYSTEM_H
#define OPHIDIAN_SRC_ENTITY_SYSTEM_ENTITY_SYSTEM_H

#include "entity.h"
#include <vector>
#include <unordered_set>
#include <assert.h>

namespace ophidian{
namespace entity_system{

using entities_storage = typename std::vector<entity>;
using entities_index_storage = typename std::vector<entity_index>;
class property;

/*
 * This class describes an entity system, which stores all its entities and pointers to the properties associated to them.
 */
class entity_system{
    entities_storage m_entities;
    entities_index_storage m_id_to_index;

    std::unordered_set<property *> m_associated_properties;

    entity m_next;
    std::size_t m_last_prealloc_qnt;

    inline void m_live_entity_check(entity_index e_index) const {
        if(e_index == invalid_entity_index)
            throw std::out_of_range("lookup::_invalid_entity");
    }

public:


    entity_system() : m_next(0), m_last_prealloc_qnt(0){

    }


    entity_system(std::size_t qnt) : m_entities(qnt), m_id_to_index(qnt), m_next(0), m_last_prealloc_qnt(0){

    }

    ~entity_system(){

    }


    std::size_t size() const { return m_entities.size(); }


    bool empty() const { return m_entities.empty(); }


    entities_storage::const_iterator begin() const { return m_entities.begin(); }


    entities_storage::const_iterator end() const { return m_entities.end(); }


    const entities_storage & entities() const { return m_entities; }


    void destroy( entity e );


    entity create();


    void preallocate(std::size_t qnt);


    void register_property(property * property);


    inline entity_index lookup(entity e) const {
        entity_index e_index = m_id_to_index.at(e);
        m_live_entity_check(e_index);
        return e_index;
    }
};

} /* namespace entity system */
} /* namespace ophidian */

#endif //OPHIDIAN_SRC_ENTITY_SYSTEM_ENTITY_SYSTEM_H