From 79ee48e0f68a3c2db2e75615cf26d4c7a239744a Mon Sep 17 00:00:00 2001
From: Stanislaw Halik <sthalik@misaki.pl>
Date: Tue, 15 Nov 2022 09:19:04 +0100
Subject: entity: add visit_tuple

---
 src/entity.hpp  | 27 ++++++++++++++++++++++++++-
 test/entity.cpp |  9 +++++++--
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/src/entity.hpp b/src/entity.hpp
index 32ab759f..31a13632 100644
--- a/src/entity.hpp
+++ b/src/entity.hpp
@@ -131,11 +131,12 @@ struct Entity final {
 };
 
 namespace detail {
+
 template<typename F, typename Tuple, std::size_t N>
 requires std::invocable<F, decltype(std::get<N>(std::declval<Tuple>()))>
 constexpr CORRADE_ALWAYS_INLINE void visit_tuple(F&& fun, Tuple&& tuple)
 {
-    using Size = std::tuple_size<std::decay_t<Tuple>>;
+    using Size = std::tuple_size<std::remove_cvref_t<Tuple>>;
     static_assert(N < Size());
 
     fun(std::get<N>(tuple));
@@ -143,6 +144,20 @@ constexpr CORRADE_ALWAYS_INLINE void visit_tuple(F&& fun, Tuple&& tuple)
         visit_tuple<F, Tuple, N+1>(std::forward<F>(fun), std::forward<Tuple>(tuple));
 }
 
+template<typename F, typename Tuple, std::size_t N>
+requires std::is_invocable_r_v<bool, F, decltype(std::get<N>(std::declval<Tuple>()))>
+constexpr CORRADE_ALWAYS_INLINE bool find_in_tuple(F&& fun, Tuple&& tuple)
+{
+    using Size = std::tuple_size<std::remove_cvref_t<Tuple>>;
+    static_assert(N < Size());
+
+    if (fun(std::get<N>(tuple)))
+        return true;
+    if constexpr(N+1 < Size())
+        return find_in_tuple<F, Tuple, N+1>(std::forward<F>(fun), std::forward<Tuple>(tuple));
+    return false;
+}
+
 } // namespace detail
 
 template<typename F, typename Tuple>
@@ -153,6 +168,16 @@ constexpr void visit_tuple(F&& fun, Tuple&& tuple)
         detail::visit_tuple<F, Tuple, 0>(std::forward<F>(fun), std::forward<Tuple>(tuple));
 }
 
+template<typename F, typename Tuple>
+constexpr bool find_in_tuple(F&& fun, Tuple&& tuple)
+{
+    using Size = std::tuple_size<std::decay_t<Tuple>>;
+    if constexpr(Size() > 0)
+        return detail::find_in_tuple<F, Tuple, 0>(std::forward<F>(fun), std::forward<Tuple>(tuple));
+    else
+        return false;
+}
+
 enum class erased_field_type : std::uint32_t {
     none,
     string,
diff --git a/test/entity.cpp b/test/entity.cpp
index 312fb18a..8266ec47 100644
--- a/test/entity.cpp
+++ b/test/entity.cpp
@@ -45,9 +45,9 @@ static constexpr bool test_accessors()
 static constexpr bool test_visitor()
 {
     {
+        constexpr auto tuple = std::make_tuple((unsigned char)1, (unsigned short)2, (int)3, (long)4);
         long ret = 0;
-        visit_tuple([&](auto x) { ret += (long)x; },
-                    std::make_tuple((unsigned char)1, (unsigned short)2, (int)3, (long)4));
+        visit_tuple([&](auto x) { ret += (long)x; }, tuple);
         fm_assert(ret == 1 + 2 + 3 + 4);
     }
     {
@@ -55,6 +55,11 @@ static constexpr bool test_visitor()
         visit_tuple([&] { ret++; }, std::tuple<>{});
         fm_assert(ret == 0);
     }
+    {
+        constexpr auto tuple = std::make_tuple((char)1, (short)2, (long)3);
+        static_assert(find_in_tuple([](auto x) { return x == 3; }, tuple));
+        static_assert(!find_in_tuple([](auto x) { return x == 5; }, tuple));
+    }
 
     return true;
 }
-- 
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