SimpleEngine/include/simpleengine/scripting/ecs_bindings.h

#pragma once

#include "entt_meta_helper.h"

#include <entt/entity/fwd.hpp>
#include <entt/entity/registry.hpp>
#include <entt/entity/runtime_view.hpp>

#include <set>

#include <sol/sol.hpp>

template <typename Component> auto is_valid(const entt::registry *registry, entt::entity entity) {
    assert(registry);
    return registry->valid(entity);
}
template <typename Component>
auto emplace_component(entt::registry *registry, entt::entity entity, const sol::table& instance, sol::this_state s) {
    assert(registry);
    auto& comp =
        registry->emplace_or_replace<Component>(entity, instance.valid() ? instance.as<Component>() : Component{});
    return sol::make_reference(s, std::ref(comp));
}
template <typename Component> auto get_component(entt::registry *registry, entt::entity entity, sol::this_state s) {
    assert(registry);
    auto& comp = registry->get_or_emplace<Component>(entity);
    return sol::make_reference(s, std::ref(comp));
}
template <typename Component> bool has_component(entt::registry *registry, entt::entity entity) {
    assert(registry);
    return registry->any_of<Component>(entity);
}
template <typename Component> auto remove_component(entt::registry *registry, entt::entity entity) {
    assert(registry);
    return registry->remove<Component>(entity);
}
template <typename Component> void clear_component(entt::registry *registry) {
    assert(registry);
    registry->clear<Component>();
}

template <typename Component> void register_meta_component() {
    using namespace entt::literals;

    entt::meta<Component>()
        .type()
        .template func<&is_valid<Component>>("valid"_hs)
        .template func<&emplace_component<Component>>("emplace"_hs)
        .template func<&get_component<Component>>("get"_hs)
        .template func<&has_component<Component>>("has"_hs)
        .template func<&clear_component<Component>>("clear"_hs)
        .template func<&remove_component<Component>>("remove"_hs);
}

auto collect_types(const sol::variadic_args& va) {
    std::set<entt::id_type> types;
    std::transform(va.cbegin(), va.cend(), std::inserter(types, types.begin()),
                   [](const auto& obj) { return deduce_type(obj); });
    return types;
}

sol::table open_registry(sol::this_state s) {
    // To create a registry inside a script: entt.registry.new()

    sol::state_view lua{s};
    auto entt_module = lua["entt"].get_or_create<sol::table>();

    entt_module.new_usertype<entt::runtime_view>("runtime_view", sol::no_constructor,
        "size_hint", &entt::runtime_view::size_hint, "contains",
        &entt::runtime_view::contains, "each",
        [](const entt::runtime_view& self, const sol::function& callback) {
            if (!callback.valid()) {
                return;   
            }
            for (auto entity : self) {
                callback(entity);
            }
        });

    using namespace entt::literals;

    entt_module.new_usertype<entt::registry>(
        "registry", sol::meta_function::construct, sol::factories([] { return entt::registry{}; }),

        "size", &entt::registry::size,

        "alive", &entt::registry::alive,

        "valid", &entt::registry::valid, "current", &entt::registry::current,

        "create", [](entt::registry& self) { return self.create(); },
        "destroy", [](entt::registry& self, entt::entity entity) { return self.destroy(entity); },

        "emplace",
        [](entt::registry& self, entt::entity entity, const sol::table& comp, sol::this_state s) -> sol::object {
            if (!comp.valid())
                return sol::lua_nil_t{};

            const auto maybe_any = invoke_meta_func(get_type_id(comp), "emplace"_hs, &self, entity, comp, s);
            return maybe_any ? maybe_any.cast<sol::reference>() : sol::lua_nil_t{};
        },
 
        "remove",
        [](entt::registry& self, entt::entity entity, const sol::object& type_or_id) {
            const auto maybe_any = invoke_meta_func(deduce_type(type_or_id), "remove"_hs, &self, entity);
            return maybe_any ? maybe_any.cast<size_t>() : 0;
        },

        "has",
        [](entt::registry& self, entt::entity entity, const sol::object& type_or_id) {
            const auto maybe_any = invoke_meta_func(deduce_type(type_or_id), "has"_hs, &self, entity);
            return maybe_any ? maybe_any.cast<bool>() : false;
        },

        "any_of",
        [](const sol::table& self, entt::entity entity, const sol::variadic_args& va) {
            const auto types = collect_types(va);
            const auto has = self["has"].get<sol::function>();
            return std::any_of(types.cbegin(), types.cend(),
                [&](auto type_id) { return has(self, entity, type_id).template get<bool>(); });
        },

        "get",
        [](entt::registry& self, entt::entity entity, const sol::object& type_or_id, sol::this_state s) {
            const auto maybe_any = invoke_meta_func(deduce_type(type_or_id), "get"_hs, &self, entity, s);
            return maybe_any ? maybe_any.cast<sol::reference>() : sol::lua_nil_t{};
        },
        
        "clear",
        sol::overload(&entt::registry::clear<>, [](entt::registry& self, sol::object type_or_id) {
            invoke_meta_func(deduce_type(type_or_id), "clear"_hs, &self);
        }),

        "orphan", &entt::registry::orphan,

        "runtime_view",
        [](entt::registry& self, const sol::variadic_args& va) {
            const std::set<uint32_t> types = collect_types(va);

            entt::runtime_view view{};
            for (const auto& type : types) {
                entt::sparse_set& storage = self.storage(type)->second;
                view.iterate(storage);
            }

            return view;
        }
    );

    return entt_module;
}