Renderive/Kernel/tests/renderive/inheritance/Inheritance_Test.cpp

#include <gtest/gtest.h>

#include "renderive/inheritance/Inheritance.hpp"

#include <type_traits>
#include <vector>

namespace {

namespace inheritance = renderive::inheritance;

struct Object_Chain {};
struct Implementation_Chain {};

enum class Registration_Position : std::size_t {
    root,
    reserved,
    implementation_parent,
    object_branch
};

constexpr auto position(Registration_Position value) noexcept {
    return static_cast<std::size_t>(value);
}

enum class Trace_Step {
    parent,
    child,
    object_branch
};

enum class Test_Payload {
    ready
};

struct Test_Event {
    Test_Payload payload{Test_Payload::ready};
};

struct Trace {
    std::vector<Trace_Step> order;
};

struct Test_Root : inheritance::Type_Root {
    explicit Test_Root(Trace& trace) : trace(&trace) {}
    Trace* trace;
};

struct Parent_Impl
    : inheritance::Dispatch_Root<
          Parent_Impl, Test_Root, Implementation_Chain, Test_Event,
          position(Registration_Position::implementation_parent)> {
    using Dispatch_Root::Dispatch_Root;

    struct Event_Handler {
        using Owner = Parent_Impl;
        static void handle(Parent_Impl& impl, const Test_Event&) {
            impl.trace->order.push_back(Trace_Step::parent);
        }
    };
    using Handler = Event_Handler;
};

struct Child_Impl
    : inheritance::Dispatch_Node<Child_Impl, Parent_Impl,
                                 Implementation_Chain, Test_Event> {
    using Dispatch_Node::Dispatch_Node;

    struct Event_Handler : Parent_Impl::Event_Handler {
        using Owner = Child_Impl;
        static void handle(Child_Impl& impl, const Test_Event&) {
            impl.trace->order.push_back(Trace_Step::child);
        }
    };
    using Handler = Event_Handler;
};

struct Object_Node
    : inheritance::Type_Node<
          Object_Node, Test_Root, Object_Chain,
          position(Registration_Position::object_branch)> {
    using Type_Node::Type_Node;
};

struct Impl_With_Object_Branch
    : inheritance::Dispatch_Node<
          Impl_With_Object_Branch, Child_Impl, Object_Chain, Test_Event,
          position(Registration_Position::object_branch)> {
    using Dispatch_Node::Dispatch_Node;

    struct Event_Handler : Child_Impl::Event_Handler {
        using Owner = Impl_With_Object_Branch;
        static void handle(Impl_With_Object_Branch& impl,
                           const Test_Event&) {
            impl.trace->order.push_back(Trace_Step::object_branch);
        }
    };
    using Handler = Event_Handler;
};

struct Reverse_Declared_Registry {
    using Inheritance_Registry = inheritance::Registry<
        inheritance::Registration<
            Implementation_Chain,
            position(Registration_Position::object_branch), Child_Impl>,
        inheritance::Registration<
            Implementation_Chain,
            position(Registration_Position::implementation_parent),
            Parent_Impl>>;

    Trace* trace;
};

using Implementation_View = inheritance::Chain_View<
    typename Child_Impl::Inheritance_Registry, Implementation_Chain>;
using Combined_Registry = inheritance::Merge_Registries_T<
    typename Child_Impl::Inheritance_Registry,
    typename Object_Node::Inheritance_Registry>;

inline constexpr std::size_t Implementation_Layer_Count =
    position(Registration_Position::object_branch) -
    position(Registration_Position::reserved);
inline constexpr std::size_t Object_Layer_Count =
    position(Registration_Position::reserved) -
    position(Registration_Position::root);

static_assert(Implementation_View::count == Implementation_Layer_Count);
static_assert(Implementation_View::next_position ==
              position(Registration_Position::object_branch) +
                  Object_Layer_Count);
static_assert(std::same_as<
              Implementation_View::Type<position(
                  Registration_Position::implementation_parent)>,
              Parent_Impl>);
static_assert(std::same_as<
              Implementation_View::Type<position(
                  Registration_Position::object_branch)>,
              Child_Impl>);
static_assert(inheritance::Chain_Registration_Count_V<
                  Combined_Registry, Implementation_Chain> ==
              Implementation_Layer_Count);
static_assert(inheritance::Chain_Registration_Count_V<Combined_Registry,
                                                      Object_Chain> ==
              Object_Layer_Count);
static_assert(std::same_as<
              inheritance::Type_At_Position_T<
                  Combined_Registry, Object_Chain,
                  position(Registration_Position::object_branch)>,
              Object_Node>);

TEST(inheritance_test, dispatches_parent_before_child) {
    Trace trace;
    Child_Impl child(trace);

    child.dispatch(Test_Event{});

    EXPECT_EQ(trace.order,
              (std::vector{Trace_Step::parent, Trace_Step::child}));
}

TEST(inheritance_test, exposes_named_registration_positions) {
    EXPECT_EQ(Parent_Impl::Inheritance_Position,
              position(Registration_Position::implementation_parent));
    EXPECT_EQ(Child_Impl::Inheritance_Position,
              position(Registration_Position::object_branch));
}

TEST(inheritance_test, dispatches_only_the_selected_chain) {
    Trace trace;
    Impl_With_Object_Branch value(trace);
    const Test_Event event{};

    value.dispatch(event);
    EXPECT_EQ(trace.order, (std::vector{Trace_Step::object_branch}));

    trace.order.clear();
    value.dispatch_for<Implementation_Chain>(event);
    EXPECT_EQ(trace.order,
              (std::vector{Trace_Step::parent, Trace_Step::child}));
}

TEST(inheritance_test, initializes_registered_layers_by_position) {
    Trace trace;
    Reverse_Declared_Registry registered{&trace};

    inheritance::initialize<Implementation_Chain>(
        registered,
        [&]<class Layer>(std::type_identity<Layer>,
                         Reverse_Declared_Registry& value) {
            if constexpr (std::same_as<Layer, Parent_Impl>)
                value.trace->order.push_back(Trace_Step::parent);
            else if constexpr (std::same_as<Layer, Child_Impl>)
                value.trace->order.push_back(Trace_Step::child);
        });

    EXPECT_EQ(trace.order,
              (std::vector{Trace_Step::parent, Trace_Step::child}));
}

TEST(inheritance_test, initializes_final_value_with_ordered_steps) {
    auto initialized = inheritance::initialize(
        Trace{},
        [](Trace& value) { value.order.push_back(Trace_Step::parent); },
        [](Trace& value) { value.order.push_back(Trace_Step::child); });

    EXPECT_EQ(initialized.order,
              (std::vector{Trace_Step::parent, Trace_Step::child}));
}

} // namespace