#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <iterator>
#include <cassert>
#include <random>
 
namespace ecs {
    namespace entity {
        using id = size_t;
        using entities = std::vector<id>;
    }
 
    namespace component {
        using name = std::string;
        using is_male = bool;
        using detail = std::pair<name, is_male>;
        using detail_component = std::pair<entity::id, detail>;
 
        enum class type { algue, Mérou, Thon, PoissonClown, Sole, Bar, Carpe };
        using type_component = std::pair<entity::id, type>;
    }
 
    namespace system {
        using details = std::vector<component::detail_component>;
        using types = std::vector<component::type_component>;
    }
 
    namespace internal {
        entity::entities _entities;
        system::details _details;
        system::types _types;
 
        std::random_device _random_device;
        std::default_random_engine _random_engine { _random_device() };
    }
 
    bool is_algue(component::type t) { return (t == component::type::algue); }
 
    bool is_poisson(component::type t) { return !is_algue(t); }
 
    bool is_carnivore(component::type t) { return (t == component::type::Mérou || 
        t == component::type::Thon || t == component::type::PoissonClown); }
 
    bool is_herbivore(component::type t) { return (t == component::type::Sole || 
        t == component::type::Bar || t == component::type::Carpe); }
 
    std::string to_string(component::type t) {
        static const std::string types[] = { "Algue", "Mérou", "Thon", "Poisson-clown", 
            "Sole", "Bar", "Carpe" };
        const auto i = static_cast<size_t>(t);
        return types[i];
    }
    
    template<typename Predicat>
    std::vector<entity::id> get_entities(Predicat&& predicat) {
        std::vector<entity::id> algues;
        std::for_each(begin(internal::_types), end(internal::_types),
            [&algues, predicat](auto p){ if (predicat(p.second)) { algues.push_back(p.first); } }
        );
        return algues;
    }
    
    template<typename Collection>
    typename Collection::value_type const& get_component(Collection const& components, entity::id id) {
        const auto it = find_if(begin(components), end(components), [id](auto p){ return (p.first == id); });
        assert(it != end(components));
        return (*it);
    }
 
    entity::id create_entity() {
        const auto id = internal::_entities.empty() ? 0 : internal::_entities.back() + 1;
        internal::_entities.push_back(id);
        return id;
    }
 
    entity::id add_algue() {
        const auto id = create_entity();
        internal::_types.push_back(std::make_pair(id, component::type::algue));
        return id;
    }
 
    entity::id add_poisson(component::type t, component::name n, component::is_male m) {
        assert(is_poisson(t));
        const auto id = create_entity();
        internal::_types.push_back(std::make_pair(id, t));
        internal::_details.push_back(std::make_pair(id, make_pair(n, m)));
        return id;
    }
 
    void remove_entity(entity::id id) {
        const auto entities_it = std::remove(internal::_entities.begin(), internal::_entities.end(), id);
        internal::_entities.erase(entities_it, internal::_entities.end());
 
        const auto details_it = std::remove_if(internal::_details.begin(), internal::_details.end(), 
            [id](auto p){ return (p.first == id); });
        internal::_details.erase(details_it, internal::_details.end());
 
        const auto types_it = std::remove_if(internal::_types.begin(), internal::_types.end(),
            [id](auto p){ return (p.first == id); });
        internal::_types.erase(types_it, internal::_types.end());
    }
    
    void remove_entities(std::vector<ecs::entity::id> const& ids) {
        for (auto id: ids) 
            remove_entity(id);
    }
 
    void print_algues() {
        const auto count = std::count_if(begin(internal::_types), end(internal::_types), 
            [](auto p){ return (p.second == component::type::algue); });
        std::cout << "algues: " << count;
    }
 
    void print_poissons() {
        if (internal::_details.empty()) {
            std::cout << "No poissons";
            return;
        }
        std::cout << internal::_details.size() << " poissons: ";
        auto print = [](auto p){ return (p.second.first + " [" + (p.second.second ? 'M' : 'F') + ']'); };
        std::transform(begin(internal::_details), end(internal::_details) - 1, 
            std::ostream_iterator<std::string>(std::cout, ", "), print);
        std::cout << print(internal::_details.back());
    }
 
    void print() {
        print_algues();
        std::cout << ". ";
        print_poissons();
        std::cout << '.' << std::endl;
    }
}
 
int main() {
    for (size_t i {}; i < 50; ++i)
        ecs::add_algue();
    for (size_t i {}; i < 10; ++i)
        ecs::add_poisson(ecs::component::type::Sole, "toto", false);
    for (size_t i {}; i < 5; ++i)
        ecs::add_poisson(ecs::component::type::Mérou, "titi", false);
    ecs::print();
 
    for (size_t tour {}; tour < 10; ++tour) {
        std::cout << "===== Tour " << tour << " ======" << std::endl;
        
        std::vector<ecs::entity::id> entities_to_remove;
        const auto poissons { ecs::get_entities(ecs::is_poisson) };
        const auto algues { ecs::get_entities(ecs::is_algue) };
        
        std::uniform_int_distribution<size_t> entities_distribution(0, ecs::internal::_entities.size() - 1);
        std::uniform_int_distribution<size_t> algue_distribution(0, algues.size() - 1);
        
        for (auto poisson: poissons) {
            auto const& poisson_type = ecs::get_component(ecs::internal::_types, poisson);
            
            if (ecs::is_herbivore(poisson_type.second) && !algues.empty()) {
                const auto index { algue_distribution(ecs::internal::_random_engine) };
                const auto target = algues[index];
                entities_to_remove.push_back(target);
            } else if (ecs::is_carnivore(poisson_type.second) && !ecs::internal::_entities.empty()) {
                const auto index { entities_distribution(ecs::internal::_random_engine) };
                const auto target = ecs::internal::_entities[index];
                entities_to_remove.push_back(target);
            }
        }
            
        ecs::remove_entities(entities_to_remove);
        ecs::print();
    }
 
    return 0;   
}