Compile type switch statement

libraries/application/tests/po/adapters/boost/log.tests.cpp

@@ -38,7 +38,7 @@ TEST_CASE_METHOD(BoostLogFixture, "Test parsing of boost log types as program op
 
     SECTION("Ensure valid value parse correctly")
     {
-        auto getLogLevel = [](std::string_view param)
+        auto const getLogLevel = [](std::string_view param)
         {
             Logging logging{};
             std::array cliOptions = { "dummyProgram.exe", "--log-level", param.data() };
@@ -68,7 +68,7 @@ TEST_CASE_METHOD(BoostLogFixture, "Test parsing of boost log types as program op
     }
     SECTION("Ensure invalid value parse correctly")
     {
-        std::array cliOptions = { "dummyProgram.exe", "--log-level", "invalid"};
+        std::array const cliOptions = { "dummyProgram.exe", "--log-level", "invalid"};
         Logging logging;
         auto const result = parseProgramOptions(static_cast<int>(cliOptions.size()), cliOptions.data(), HelpDocumentation{}, logging);
         REQUIRE(result);

libraries/core/src/morpheus/core/conformance/source_location.hpp

@@ -4,6 +4,10 @@
     #include <source_location>
 #endif
 
+/// \namespace morpheus::sl_ns
+///     Conformance namespace abstracting the underlying source_location while compilers do not offer uniform support.
+///     When support is missing falls back to boost::source_location.
+
 // clang-format off
 #if (__cpp_lib_source_location >= 201907L)
 

libraries/core/src/morpheus/core/functional/CMakeLists.txt

@@ -2,4 +2,5 @@ target_sources(MorpheusCore
     PUBLIC
         function_ref.hpp
         overload.hpp
+        switch.hpp
 )

libraries/core/src/morpheus/core/functional/switch.hpp

@@ -0,0 +1,115 @@
+#pragma once
+
+#include <morpheus/core/conformance/unreachable.hpp>
+
+#include <boost/hana/first.hpp>
+#include <boost/hana/pair.hpp>
+#include <boost/hana/second.hpp>
+#include <boost/mp11.hpp>
+#include <boost/preprocessor/repetition.hpp>
+#include <concepts>
+#include <tuple>
+#include <type_traits>
+
+namespace morpheus::functional
+{
+
+/// \struct CaseList
+///     Typelist to hold cases for the switch
+template<typename... Cases>
+struct CaseList
+{
+};
+
+constexpr auto switchCaseElement(auto case_, auto f) { return f(case_); }
+constexpr auto switchCondition(auto case_) { return switchCaseElement(case_, boost::hana::first); }
+constexpr auto switchTag(auto case_) { return switchCaseElement(case_, boost::hana::second); }
+
+#ifndef MORPHEUS_SWITCH_MAX
+    #define MORPHEUS_SWITCH_MAX 64
+#endif
+
+inline constexpr auto defaultCase = [](auto unhandledValue){};
+
+template<class CT, CT C, class T = std::integral_constant<CT, C>>
+using SwitchCase = boost::hana::pair<std::integral_constant<CT, C>, T>;
+
+namespace detail {
+
+#define MORPHEUS_SWITCH_CASE(Z, N, _)                                                                                                                          \
+    case decltype(switchCondition(boost::mp11::mp_at_c<CaseList, N>{}))::value:                                                                                \
+        return std::forward<CaseHandler>(caseHander)(decltype(switchTag(boost::mp11::mp_at_c<CaseList, N>{})){});
+
+template<class Result, class Condition, class DefaultHandler>
+Result invokeDefaultHandler(Condition condition, DefaultHandler defaultHandler)
+{
+    if constexpr (!std::is_void_v<Result> && std::is_void_v<std::invoke_result_t<DefaultHandler, Condition>>)
+    {
+        defaultHandler(condition);
+        unreachable();
+    }
+    else
+        return defaultHandler(condition);
+}
+
+#define MORPHEUS_SWITCH_OVERLOAD(Z, N, _)                                                                                                                      \
+    template <class Result, class Condition, class CaseList, class CaseHandler, class DefaultCase>                                                             \
+    constexpr Result switch_(std::integral_constant<std::size_t, N>, Condition const condition, CaseList const cases, CaseHandler&& caseHander,                \
+                             DefaultCase&& defaultCase)                                                                                                        \
+    {                                                                                                                                                          \
+        switch (condition) {                                                                                                                                   \
+            BOOST_PP_REPEAT_##Z(N, MORPHEUS_SWITCH_CASE, ~)                                                                                                    \
+        }                                                                                                                                                      \
+        return invokeDefaultHandler<Result, Condition, DefaultCase>(condition, defaultCase);                                                                   \
+    }
+
+BOOST_PP_REPEAT(MORPHEUS_SWITCH_MAX, MORPHEUS_SWITCH_OVERLOAD, ~)
+#undef MORPHEUS_SWITCH_CASE
+#undef MORPHEUS_SWITCH_OVERLOAD
+
+template<class... T> struct SwitchCommonReference {
+    using type = std::conditional_t<(std::is_rvalue_reference_v<T> && ...), std::add_rvalue_reference_t<std::common_type_t<T...>>,
+                 std::conditional_t<(std::is_reference_v<T> && ...), std::add_lvalue_reference_t<std::common_type_t<T...>>,
+                 std::common_type_t<T...>>>;
+};
+
+template<class Condition, class CaseList, class CaseHandler, class DefaultHandler>
+auto switchResult(CaseList caseList)
+{
+    constexpr std::size_t Size = boost::mp11::mp_size<CaseList>::value;
+    if constexpr (Size == 0u)
+        return std::invoke_result<DefaultHandler, Condition>{};
+    else
+        return [&]<std::size_t... I>(std::index_sequence<I...>)
+        {
+            return SwitchCommonReference<
+                std::invoke_result_t<CaseHandler, decltype(switchTag(boost::mp11::mp_at_c<CaseList, I>{}))>...>{};
+        }(std::make_index_sequence<Size>{});
+}
+
+template<class Condition, class CaseList, class CaseHandler, class DefaultHandler>
+using SwitchResult = typename decltype(switchResult<Condition, CaseList, CaseHandler, DefaultHandler>(std::declval<CaseList>()))::type;
+
+}
+
+/// Compile time generation of switch statements.  Maps a given list of values  This is
+///
+template<class Condition, class CaseList, class CaseHandler, class DefaultCase = decltype(defaultCase)>
+constexpr detail::SwitchResult<Condition, CaseList, CaseHandler, DefaultCase> switch_(
+    Condition const condition, /// The switch conditional value to be executed.
+    CaseList const caseList, /// List of case predicates.
+    CaseHandler&& caseHander, /// Handler for case statement bodies.
+    DefaultCase&& defaultCase = DefaultCase{} /// Handler for the default statement of the switch.
+)
+{
+    constexpr std::size_t Size = boost::mp11::mp_size<CaseList>::value;
+    static_assert(Size < MORPHEUS_SWITCH_MAX, "Increase MORPHEUS_SWITCH_MAX");
+    using Result = detail::SwitchResult<Condition, CaseList, CaseHandler, DefaultCase>;
+    return detail::switch_<Result, Condition, CaseList, CaseHandler, DefaultCase>
+        (std::integral_constant<std::size_t, Size>{}, condition, caseList,
+        std::forward<CaseHandler>(caseHander),
+        std::forward<DefaultCase>(defaultCase)
+    );
+}
+
+}

libraries/core/tests/functional/CMakeLists.txt

@@ -1,4 +1,5 @@
 target_sources(MorpheusCoreTests
     PRIVATE
         function_ref.tests.cpp
+        switch.tests.cpp
 )

libraries/core/tests/functional/switch.tests.cpp

@@ -0,0 +1,112 @@
+#include "morpheus/core/functional/switch.hpp"
+
+#include <boost/hana/size.hpp>
+#include <boost/hana/transform.hpp>
+#include <boost/hana/tuple.hpp>
+#include <boost/hana/zip.hpp>
+#include <boost/mp11.hpp>
+#include <catch2/catch_all.hpp>
+#include <magic_enum_format.hpp>
+
+#include <tuple>
+
+namespace hana = boost::hana;
+using namespace hana::literals;
+
+namespace morpheus::functional
+{
+
+/*
+// clang-format off
+struct ReturnLValueReference
+{
+    bool a;
+    char b;
+    int c;
+    float d;
+
+    bool& operator()(bool) { return a; }
+    char& operator()(char) { return b; }
+    int& operator()(int) { return c; }
+    float& operator()(float) { return d; }
+};
+
+// struct ReturnRValueReference
+// {
+//     std::tuple<bool, char, int, float> values;
+
+//     bool&& operator()(bool) { return std::get<0>(values); }
+//     char&& operator()(char) { return std::get<1>(values); }
+//     int&& operator()(int) { return std::get<2>(values); }
+//     float&& operator()(float) { return std::get<3>(values); }
+// };
+
+// clang-format on
+
+TEST_CASE("Verify switch cases returning a value", "[morpheus.functional.switch.value]")
+{
+    using Cases = CaseList<SwitchCase<int, 0>, SwitchCase<int, 1>, SwitchCase<int, 2>, SwitchCase<int, 3>>;
+    STATIC_REQUIRE(boost::mp11::mp_size<Cases>::value == 4);
+    for (int i = 0; i < boost::mp11::mp_size<Cases>::value; ++i) {
+        auto const result = switch_(i, Cases{},
+                                    [](auto const caseValue)
+                                    {
+                                        return caseValue;
+                                    });
+        REQUIRE(result == i);
+    }
+}
+
+TEST_CASE("Verify switch cases returning a lvalue-reference", "[morpheus.functional.switch.lvalue_reference]")
+{
+    // auto types = boost::hana::tuple_t<bool, char, int, float>;
+    // auto caseValues = []<std::size_t... Is>(std::index_sequence<Is...>)
+    // {
+    //     return boost::hana::tuple_c<std::size_t, Is...>;
+    // }(std::make_index_sequence<boost::hana::size(types)>());
+    // auto caseParams = boost::hana::zip(types, caseValues);
+    // auto cases = boost::hana::transform(caseParams,
+    //                                     [](auto const params)
+    //                                     {
+    //                                         return SwitchCase<decltype(+params[1_c]), +params[1_c], decltype(params[0_c])>;
+    //                                     });
+
+    // using CaseTypes = std::tuple<bool, char, int, float>;
+    // using CaseValues = boost::mp11::mp_iota_c<4>;
+    // using Case = boost::hana::transform
+    // using Cases = boost::mp11::mp_transform<
+
+    using Cases = CaseList<SwitchCase<int, 0, bool>, SwitchCase<int, 1, char>, SwitchCase<int, 2, int>, SwitchCase<int, 3, float>>;
+    STATIC_REQUIRE(boost::mp11::mp_size<Cases>::value == 4);
+
+    ReturnLValueReference expected;
+    auto const& result = switch_(3, Cases{}, std::ref(expected));
+    REQUIRE(&result == &expected.d);
+}
+
+TEST_CASE("Verify switch cases returning a rvalue-reference", "[morpheus.functional.switch.rvalue_reference]") {}
+*/
+
+TEST_CASE("Enumerate switch cases for each enum entry", "[morpheus.functional.switch.enum]")
+{
+    enum class Case
+    {
+        A,
+        B,
+        C,
+        D
+    };
+    using Cases = CaseList<SwitchCase<Case, Case::A>, SwitchCase<Case, Case::B>, SwitchCase<Case, Case::C>, SwitchCase<Case, Case::D>>;
+    STATIC_REQUIRE(boost::mp11::mp_size<Cases>::value == magic_enum::enum_count<Case>());
+    magic_enum::enum_for_each<Case>(
+        [](auto const caseToCall)
+        {
+            switch_(caseToCall, Cases{},
+                    [&](auto const executedCase)
+                    {
+                        REQUIRE(caseToCall == executedCase);
+                    });
+        });
+}
+
+} // namespace morpheus::functional