Add util/random, demo in app (#5)

Author: karnkaul

CMakeLists.txt

@@ -23,3 +23,5 @@ file(GLOB_RECURSE sources LIST_DIRECTORIES false "src/*.[hc]pp")
 target_sources(${PROJECT_NAME} PRIVATE
   ${sources}
 )
+
+target_precompile_headers(${PROJECT_NAME} REUSE_FROM le2d)

src/app.cpp

@@ -4,6 +4,7 @@
 #include <game.hpp>
 #include <klib/visitor.hpp>
 #include <log.hpp>
+#include <util/random.hpp>
 
 namespace miracle {
 namespace {
@@ -18,6 +19,7 @@ App::App() : m_context(context_ci), m_data_loader(le::FileDataLoader::upfind("as
 	// test code, remove later.
 	auto json = dj::Json{};
 	if (m_services.get<le::IDataLoader>().load_json(json, "test_file.json")) { log.info("loaded JSON: {}", json); }
+	log.debug("random_range(1, 100): {}", util::random_range(1, 100));
 }
 
 void App::run() {

src/util/random.hpp

@@ -0,0 +1,37 @@
+#pragma once
+#include <klib/assert.hpp>
+#include <klib/concepts.hpp>
+#include <random>
+
+namespace miracle::util {
+/// \brief Wrapper that reuses the same random engine for all calls.
+class Random {
+  public:
+	template <klib::NumberT Type>
+	[[nodiscard]] static auto in_range(Type const min, Type const max) -> Type {
+		if constexpr (std::integral<Type>) {
+			auto dist = std::uniform_int_distribution<Type>{min, max};
+			return dist(m_engine);
+		} else {
+			auto dist = std::uniform_real_distribution<Type>{min, max};
+			return dist(m_engine);
+		}
+	}
+
+  private:
+	inline static std::default_random_engine m_engine{std::random_device{}()};
+};
+
+/// \returns Random value in the range [min, max].
+template <klib::NumberT Type>
+[[nodiscard]] auto random_range(Type const min, Type const max) -> Type {
+	return Random::in_range(min, max);
+}
+
+/// \returns Random index in the range [0, size - 1].
+/// \pre size must be greater than 0.
+[[nodiscard]] inline auto random_index(std::size_t const size) -> std::size_t {
+	KLIB_ASSERT(size > 0);
+	return Random::in_range(0uz, size - 1);
+}
+} // namespace miracle::util