From 38d7045685d4904d013ea4990a3aa7f5e78309cf Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 22 Oct 2022 17:57:47 +0100
Subject: Add magic support to printing/parsing/validating enumerations

---
 lib/enumDetails.hpp | 133 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 133 insertions(+)
 create mode 100644 lib/enumDetails.hpp

(limited to 'lib/enumDetails.hpp')

diff --git a/lib/enumDetails.hpp b/lib/enumDetails.hpp
new file mode 100644
index 0000000..ace6252
--- /dev/null
+++ b/lib/enumDetails.hpp
@@ -0,0 +1,133 @@
+#pragma once
+
+#include <algorithm>
+#include <array>
+#include <limits>
+#include <optional>
+#include <string_view>
+
+/// EnumTypeDetails
+// Extracts the fully qualified name of the enumeration
+template<typename E> struct EnumTypeDetails {
+#ifndef ENUM_PROBE
+protected:
+#endif
+	constexpr static std::string_view SEARCH_TYPE {"E = "};
+	constexpr static auto
+	typeraw()
+	{
+		return std::string_view {__PRETTY_FUNCTION__};
+	};
+	constexpr static auto typeNameStart {typeraw().find(SEARCH_TYPE) + SEARCH_TYPE.length()};
+	constexpr static auto typeNameEnd {typeraw().find_first_of("];", typeNameStart)};
+	constexpr static auto typeNameLen {typeNameEnd - typeNameStart};
+	constexpr static auto typeNameArr {[]() {
+		std::array<char, typeNameLen> out;
+		typeraw().copy(out.begin(), typeNameEnd - typeNameStart, typeNameStart);
+		return out;
+	}()};
+
+public:
+	constexpr static std::string_view typeName {typeNameArr.data(), typeNameArr.size()};
+};
+
+/// EnumValueDetails
+// Extracts the value name and constructs string_views of the parts
+template<auto value> struct EnumValueDetails : public EnumTypeDetails<decltype(value)> {
+#ifndef ENUM_PROBE
+private:
+#endif
+	using T = EnumTypeDetails<decltype(value)>;
+	constexpr static auto
+	raw()
+	{
+		return std::string_view {__PRETTY_FUNCTION__};
+	};
+	constexpr static auto nameStart {raw().find_last_of(": ") + 1};
+	constexpr static auto nameEnd {raw().find_first_of("];", nameStart)};
+	constexpr static auto nameLen {nameEnd - nameStart};
+	constexpr static auto nameArr {[]() {
+		std::array<char, nameLen> out;
+		raw().copy(out.begin(), nameLen, nameStart);
+		return out;
+	}()};
+
+public:
+	constexpr static std::string_view valueName {nameArr.data(), nameArr.size()};
+	constexpr static auto valid {valueName.back() < '0' || valueName.back() > '9'};
+	constexpr static auto raw_value {value};
+};
+
+template<typename E> struct EnumValueCollection {
+	using Vs = std::make_integer_sequence<int, 256>;
+};
+
+template<typename E> struct EnumDetails {
+public:
+	using EVC = EnumValueCollection<E>;
+
+#ifndef ENUM_PROBE
+private:
+#endif
+	template<auto... n>
+	constexpr static auto
+	get_valids(std::integer_sequence<int, n...>)
+	{
+		return std::array {EnumValueDetails<static_cast<E>(n)>::valid...};
+	}
+	template<auto... n>
+	constexpr static auto
+	get_values(std::integer_sequence<int, n...>)
+	{
+		return std::array {EnumValueDetails<static_cast<E>(n)>::raw_value...};
+	}
+	template<auto... n>
+	constexpr static auto
+	get_valueNames(std::integer_sequence<int, n...>)
+	{
+		return std::array {EnumValueDetails<values[n]>::valueName...};
+	}
+
+	constexpr static auto valid_flags {get_valids(typename EVC::Vs {})};
+	constexpr static auto valid_count {std::count_if(valid_flags.begin(), valid_flags.end(), std::identity {})};
+
+public:
+	constexpr static auto values {[]() {
+		constexpr auto values {get_values(typename EVC::Vs {})};
+		static_assert(std::is_sorted(values.begin(), values.end()), "Candidate values must be sorted");
+		std::array<E, valid_count> out;
+		auto write = out.begin();
+		for (auto v = values.begin(); const bool & valid : valid_flags) {
+			if (valid) {
+				*write++ = static_cast<E>(*v);
+			}
+			++v;
+		}
+		return out;
+	}()};
+	constexpr static auto names {get_valueNames(std::make_integer_sequence<int, valid_count> {})};
+
+	constexpr static bool
+	is_valid(E value) noexcept
+	{
+		return std::binary_search(values.begin(), values.end(), value);
+	}
+
+	constexpr static std::optional<E>
+	parse(std::string_view name) noexcept
+	{
+		if (const auto itr = std::find(names.begin(), names.end(), name); itr != names.end()) {
+			return values[std::distance(names.begin(), itr)];
+		}
+		return std::nullopt;
+	}
+
+	constexpr static std::optional<std::string_view>
+	to_string(E value) noexcept
+	{
+		if (const auto itr = std::find(values.begin(), values.end(), value); itr != values.end()) {
+			return names[std::distance(values.begin(), itr)];
+		}
+		return std::nullopt;
+	}
+};
-- 
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