Add queries/systems support

tests/zecsy.cpp

@@ -1,4 +1,5 @@
 #include <catch2/catch_test_macros.hpp>
+#include <concepts>
 #include <string>
 #define CATCH_CONFIG_MAIN
 #include <catch2/catch_all.hpp>
@@ -202,4 +203,60 @@ TEST_CASE("Create a simple system that processes entities with a specific compon
 
     REQUIRE(e0.get<Component>().value == 0);
     REQUIRE(e1.get<Component>().value == 20);
+   
+    /*
+     * Really wanna deduce it to w.query([](Component&){}),
+     * but I have some troubles with it
+     */
+    w.query<Component>([](Component& c) 
+    {
+        c.value++;
+    });
+
+    REQUIRE(e0.get<Component>().value == 1);
+    REQUIRE(e1.get<Component>().value == 21);
+}
+
+TEST_CASE("Test a system’s ability to query and process only entities with a specific combination of components")
+{
+    struct C0 
+    {
+        int value = 0;
+    };
+
+    struct C1
+    {
+        int value = 10;
+    };
+
+    world w;
+
+    auto e0 = w.make_entity();
+    e0.set(C0{}, C1{});
+
+    auto e1 = w.make_entity();
+    e1.set(C0{});
+
+    auto e2 = w.make_entity();
+    e2.set(C1{});
+
+    int count = 0;
+
+    REQUIRE(e0.get<C0>().value == 0);
+    REQUIRE(e0.get<C1>().value == 10);
+
+    w.query<C0, C1>([&count](C0& c0, C1& c1)
+    {
+        c0.value++;
+        c1.value++;
+    });
+
+    REQUIRE(e0.get<C0>().value == 1);
+    REQUIRE(e0.get<C1>().value == 11);
+
+    REQUIRE(e1.get<C0>().value == 0);
+    REQUIRE(e2.get<C1>().value == 10);
+
+    REQUIRE_FALSE(e1.has<C1>());
+    REQUIRE_FALSE(e2.has<C0>());
 }

zecsy.hpp

@@ -2,6 +2,7 @@
 #include <catch2/internal/catch_console_colour.hpp>
 #include <cstdint>
 #include <format>
+#include <functional>
 #include <queue>
 #include <stdexcept>
 #include <typeindex>
@@ -121,6 +122,9 @@ namespace zecsy
 
         template<typename... T>
         void remove(entity_id e);
+
+        template<typename... T, typename Callable>
+        void query(Callable&& system);
     private:
         entities_set alive_entities;
         entity_id entity_counter = 0;
@@ -321,4 +325,16 @@ namespace zecsy
         remove<Second>(e);
         (remove<Rest>(e), ...);
     }
+
+    template<typename... T, typename Callable>
+    inline void world::query(Callable&& system)
+    {
+        for(auto e: alive_entities)
+        {
+            if((has<T...>(e)))
+            {
+                system(get<T>(e)...);
+            }
+        }
+    }
 };