add Chapter18

Chapter18/cib/libs/log/level.hpp

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+#pragma once
+
+#include <log/env.hpp>
+
+#include <stdx/type_traits.hpp>
+
+#include <array>
+#include <cstdint>
+#include <string_view>
+#include <type_traits>
+#include <utility>
+
+namespace logging {
+// enum assignment is according to Mipi_Sys-T Severity definition
+enum struct level : std::uint8_t {
+    MAX = 0,
+    FATAL = 1,
+    ERROR = 2,
+    WARN = 3,
+    INFO = 4,
+    USER1 = 5,
+    USER2 = 6,
+    TRACE = 7
+};
+
+template <level L>
+[[nodiscard]] constexpr auto to_text() -> std::string_view
+    requires(L <= level::TRACE)
+{
+    using namespace std::string_view_literals;
+    constexpr std::array level_text{"MAX"sv,  "FATAL"sv, "ERROR"sv, "WARN"sv,
+                                    "INFO"sv, "USER1"sv, "USER2"sv, "TRACE"sv};
+    return level_text[stdx::to_underlying(L)];
+}
+
+[[maybe_unused]] constexpr inline struct get_level_t {
+    template <typename T>
+    CONSTEVAL auto operator()(T &&t) const noexcept(
+        noexcept(std::forward<T>(t).query(std::declval<get_level_t>())))
+        -> decltype(std::forward<T>(t).query(*this)) {
+        return std::forward<T>(t).query(*this);
+    }
+} get_level;
+} // namespace logging