Add compile time checked variant (needs C++20)

3 files changed, 266 insertions, 10 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5f75a25..49b8ecc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.0)
 
-set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 project(cxxformat)
diff --git a/cxxformat.hpp b/cxxformat.hpp
index b02fe4f..6a86e4c 100644
--- a/cxxformat.hpp
+++ b/cxxformat.hpp
@@ -52,7 +52,7 @@ template<typename From>
 struct FormatConvert<double, From, std::enable_if_t<std::is_convertible_v<From, double> && !std::is_integral_v<From>>> : ImplicitConversion<double, const From &> {};
 
 template<typename Pointer>
-struct FormatConvert<const void *, Pointer, std::enable_if_t<std::is_pointer_v<Pointer> && !std::is_array_v<std::remove_pointer_t<Pointer>> && !std::is_same_v<std::remove_pointer_t<Pointer>, char>>> : ImplicitConversion<const void *, const Pointer *> {};
+struct FormatConvert<const void *, Pointer, std::enable_if_t<std::is_pointer_v<Pointer> && !std::is_array_v<std::remove_pointer_t<Pointer>>>> : ImplicitConversion<const void *, const Pointer> {};
 
 template<typename Pointer>
 struct FormatConvert<const void *, Pointer, std::enable_if_t<std::is_pointer_v<Pointer> && std::is_array_v<std::remove_pointer_t<Pointer>>>> : ImplicitConversion<const void*, const Pointer> {};
@@ -60,7 +60,7 @@ struct FormatConvert<const void *, Pointer, std::enable_if_t<std::is_pointer_v<P
 template<typename From, typename Enable = void>
 struct AutoConversion
 {
-	static std::string conversion(const From &)
+	static bool conversion(const From &)
 	{
 		throw FormatException{""};
 	}
@@ -69,9 +69,9 @@ struct AutoConversion
 template<char Conversion, typename From>
 struct SimpleAutoConversion
 {
-	static std::string conversion(const From &)
+	static constexpr char conversion(const From &)
 	{
-		return std::string{Conversion};
+		return Conversion;
 	}
 };
 
@@ -201,11 +201,29 @@ namespace detail
 	template<typename From>
 	using string_or_string_view = typename StringOrStringViewHelper<From>::type;
 
-	template<bool allowPointer = false, typename From>
-	std::string autoConversionSpecifier(From &&from, std::size_t index = 0)
+	template<bool allowPointer = false, bool allowFallback = true, typename From>
+	constexpr char autoConversionSpecifier(From &&from, std::size_t index = 0)
 	{
 		try
 		{
+			if constexpr (!allowFallback)
+			{
+				if constexpr(!std::is_same_v<char, decltype(AutoConversion<remove_cvref_t<From>>::conversion(std::forward<From>(from)))>)
+				{
+					if constexpr (std::is_pointer_v<From>)
+					{
+						if constexpr (allowPointer)
+						{
+							return 'p';
+						}
+						else
+						{
+							if constexpr (!allowFallback) static_assert(allowPointer, "%v doesn't allow automatic conversions for pointers; use %V to alsow allow arbitrary pointers");
+							else throw FormatException{"Argument#" + std::to_string(index) + " is not applicable for auto conversion with %v, use %V to also allow arbitrary pointers"};
+						}
+					}
+				}
+			}
 			return AutoConversion<remove_cvref_t<From>>::conversion(std::forward<From>(from));
 		}
 		catch (const FormatException &)
@@ -214,10 +232,11 @@ namespace detail
 			{
 				if constexpr (allowPointer)
 				{
-					return "p";
+					return 'p';
 				}
 				else
 				{
+					if constexpr (!allowFallback) static_assert(allowPointer, "%v doesn't allow automatic conversions for pointers; use %V to alsow allow arbitrary pointers");
 					throw FormatException{"Argument#" + std::to_string(index) + " is not applicable for auto conversion with %v, use %V to also allow arbitrary pointers"};
 				}
 			}
@@ -378,4 +397,240 @@ std::string format(const String &fmt, Args &&... args)
 	}
 }
 
+template<size_t i>
+struct str_index { static constexpr size_t n = i; };
+
+template<size_t N>
+struct str
+{
+public:
+	const char s[N + 1];
+	static constexpr size_t size = N;
+
+private:
+	template<size_t... indices>
+	constexpr str<N + 1> appendCharHelper(const char c, std::index_sequence<indices...>) const
+	{
+		return str<N + 1>{s[indices]..., c, '\0'};
+	}
+
+	template<size_t... indices>
+	static constexpr str<N + 1> prependCharHelper(const char c, const str<N> &s, std::index_sequence<indices...>)
+	{
+		return str<N + 1>{c, s.s[indices]..., '\0'};
+	}
+
+	template<auto other, size_t... ownIndices, size_t... othersIndices>
+	constexpr str<N + sizeof...(othersIndices)> appendStrHelper(std::index_sequence<ownIndices...>, std::index_sequence<othersIndices...>) const
+	{
+		return str<N + sizeof...(othersIndices)>{s[ownIndices]..., other.s[othersIndices]..., '\0'};
+	}
+public:
+
+	template<size_t index>
+	constexpr char get(str_index<index>) const
+	{
+		static_assert(index < N, "str::get: index out of range");
+		return s[index];
+	}
+
+	template<size_t offset, size_t... indices>
+	constexpr str<sizeof...(indices)> extract(std::index_sequence<indices...>, str_index<offset> = str_index<0>{}) const
+	{
+		static_assert(((indices + offset < N) && ...), "str::extract: index out of range");
+		return str<sizeof...(indices)>{s[indices + offset]..., '\0'};
+	}
+
+	constexpr str<N + 1> operator+(const char c) const
+	{
+		return appendCharHelper(c, std::make_index_sequence<N>());
+	}
+
+	template<size_t otherN>
+	constexpr str<N + otherN> operator+(const str<otherN> &other) const
+	{
+		return appendStrHelper<other>(std::make_index_sequence<N>(), std::make_index_sequence<otherN>());
+	}
+
+	template<size_t _N>
+	friend constexpr str<_N + 1> operator+(const char c, const str<_N> &other);
+};
+
+template<size_t N>
+constexpr str<N + 1> operator+(const char c, const str<N> &other)
+{
+	return str<N>::prependCharHelper(c, other, std::make_index_sequence<N>());
+}
+
+template<size_t N>
+str(const char(&)[N]) -> str<N - 1>;
+
+namespace detail
+{
+	template<size_t i, size_t N>
+	constexpr char get(const str<N>& s)
+	{
+		return s.get(str_index<i>{});
+	}
+
+	template<size_t N, size_t offset, size_t... indices>
+	constexpr str<sizeof...(indices)> extractStr(const str<N> &source, std::index_sequence<indices...>)
+	{
+		return str<sizeof...(indices)>{get<indices + offset>(source)..., '\0'};
+	}
+
+	template<size_t start, size_t end = std::string::npos, bool endIsIndex = false, size_t N>
+	constexpr str<end == std::string::npos ? N - start : (endIsIndex ? end + 1 - start : end)> substr(const str<N> &s)
+	{
+		static_assert(!endIsIndex || end < N, "End index / substr-length is out of range");
+		if constexpr (end == std::string::npos) return substr<start, N - 1, true>(s);
+		else if constexpr (!endIsIndex) return substr<start, start + end - 1, true>(s);
+		else if constexpr (endIsIndex && end + 1 - start == 0) return str{""};
+		else return s.extract(std::make_index_sequence<end - start + 1>(), str_index<start>{});
+	}
+
+	template<typename T, auto s, size_t i = 0, bool allowSign = true, T parsedPart = 0>
+	constexpr T strToInt()
+	{
+		if constexpr (i == s.size) return parsedPart;
+		else
+		{
+			constexpr char c = get<i>(s);
+			if constexpr (c == '-')
+			{
+				static_assert(allowSign, "strToInt: invalid character found");
+				static_assert(std::is_signed_v<T>, "strToInt: negative sign found when converting to an unsigned type");
+				return -strToInt<T, s, i + 1, false>();
+			}
+			else if constexpr (c == '+')
+			{
+				static_assert(allowSign, "strToInt: invalid character found");
+				return strToInt<T, s, i + 1, false>();
+			}
+			else
+			{
+				static_assert(c >= '0' && c <= '9', "strToInt: invalid character found");
+				return strToInt<T, s, i + 1, false, parsedPart * T{10} + T{c - '0'}>();
+			}
+		}
+	}
+
+	template<typename T, T N>
+	constexpr size_t decimalLength()
+	{
+		if constexpr (N < 0) return 1 + decimalLength<T, -N>();
+		else if constexpr (N < 10) return 1;
+		else return 1 + decimalLength<T, N / 10>();
+	}
+
+	template<typename T, T N>
+	constexpr str<decimalLength<T, N>()> toStr()
+	{
+		if constexpr (N < 0) return '-' + toStr<T, -N>();
+		else if constexpr (N < 10)
+		{
+			return str<1>{'0' + N};
+		}
+		else return toStr<T, N / 10>() + char(N % 10 + '0');
+	};
+
+	template<auto fmt, size_t i, size_t argumentIndex>
+	std::string format_s()
+	{
+		if constexpr (i == fmt.size) return "";
+		else if constexpr (get<i>(fmt) == '%')
+		{
+			if constexpr (get<i + 1>(fmt) == '%') return substr<0, i, true>(fmt).s + format_s<substr<i + 2>(fmt), 0, argumentIndex>();
+			else
+			{
+				static_assert(get<i + 1>(fmt) == '%', "Not enough arguments passed");
+				throw FormatException{"Not enough arguments passed"};
+			}
+		}
+		else return format_s<fmt, i + 1, argumentIndex>();
+	}
+
+	template<auto fmt, size_t i>
+	constexpr std::pair<char, size_t> getFlag()
+	{
+		constexpr char next = get<i>(fmt);
+		if constexpr (next == '#' || next == '0' || next == '-' || next == ' ' || next == '+') return {next, i + 1};
+		else return {0, i};
+	}
+
+	template<auto fmt, size_t i>
+	constexpr size_t getNumberEnd()
+	{
+		if constexpr (std::isdigit(get<i>(fmt))) return getNumberEnd<fmt, i + 1>();
+		else return i;
+	}
+
+	template<char conversion, size_t argumentIndex, typename Arg>
+	constexpr char checkReplaceAutoConversion(Arg &&arg)
+	{
+		if constexpr (conversion == 'v' || conversion == 'V') return autoConversionSpecifier<conversion == 'V', false>(std::forward<Arg>(arg), argumentIndex);
+		else return conversion;
+	}
+
+	template<bool havePrecision, auto fmt, size_t iAfterFieldWidth, size_t iAfterPrecision, typename String>
+	size_t determineStringPrecision(const String& string)
+	{
+		if constexpr (havePrecision) return std::min(strToInt<size_t, substr<iAfterFieldWidth + 1, iAfterPrecision - 1, true>(fmt)>(), string.size());
+		else return string.size();
+	}
+
+	template<auto fmt, char conversion, size_t i, size_t iAfterPrecision, char length>
+	constexpr auto makeDirective()
+	{
+		if constexpr (length) return substr<i, iAfterPrecision - 1, true>(fmt) + length + conversion;
+		else return substr<i, iAfterPrecision - 1, true>(fmt) + conversion;
+	}
+
+	template<auto fmt, size_t i, size_t argumentIndex, typename Arg, typename... Args>
+	std::string format_s(Arg &&arg, Args &&...args)
+	{
+		static_assert(i < fmt.size, "Too many arguments passed");
+		if constexpr (i == fmt.size)
+		{
+			throw FormatException{std::to_string(argumentIndex - 1) + " placeholders found, but " + std::to_string(argumentIndex + sizeof...(args)) + " arguments passed"};
+		}
+		else if constexpr (get<i>(fmt) == '%')
+		{
+			if constexpr (get<i + 1>(fmt) == '%') return substr<0, i, true>(fmt).s + format_s<substr<i + 2>(fmt), 0, argumentIndex>(std::forward<Arg>(arg), std::forward<Args>(args)...);
+
+			constexpr auto flagData = getFlag<fmt, i + 1>();
+			constexpr char flag = flagData.first;
+			constexpr char iAfterFlag = flagData.second;
+			constexpr size_t iAfterFieldWidth = getNumberEnd<fmt, iAfterFlag>();
+
+			constexpr auto havePrecision = get<iAfterFieldWidth>(fmt) == '.';
+			constexpr size_t iAfterPrecision = [havePrecision, iAfterFieldWidth]() -> size_t { if constexpr (havePrecision) return getNumberEnd<fmt, iAfterFieldWidth + 1>(); else return iAfterFieldWidth; }();
+
+			constexpr char conversion = checkReplaceAutoConversion<get<iAfterPrecision>(fmt), argumentIndex>(std::forward<Arg>(arg));
+
+			if constexpr (conversion == 'c') return substr<0, i - 1, true>(fmt).s + strprintf(makeDirective<fmt, conversion, i, iAfterPrecision, 0>().s, convert<char, false>(std::forward<Arg>(arg), "character", argumentIndex)) + format_s<substr<iAfterPrecision + 1>(fmt), 0, argumentIndex + 1>(std::forward<Args>(args)...);
+			else if constexpr (conversion == 'd' || conversion == 'i') return substr<0, i - 1, true>(fmt).s + strprintf(makeDirective<fmt, conversion, i, iAfterPrecision, 'j'>().s, convert<std::intmax_t, false>(std::forward<Arg>(arg), "signed integer", argumentIndex)) + format_s<substr<iAfterPrecision + 1>(fmt), 0, argumentIndex + 1>(std::forward<Args>(args)...);
+			else if constexpr (conversion == 'u' || conversion == 'o' || conversion == 'x' || conversion == 'X') return substr<0, i - 1, true>(fmt).s + strprintf(makeDirective<fmt, conversion, i, iAfterPrecision, 'j'>().s, convert<std::uintmax_t, false>(std::forward<Arg>(arg), "unsigned integer", argumentIndex)) + format_s<substr<iAfterPrecision + 1>(fmt), 0, argumentIndex + 1>(std::forward<Args>(args)...);
+			else if constexpr (conversion == 'e' || conversion == 'E' || conversion == 'f' || conversion == 'F' || conversion == 'g' || conversion == 'G' || conversion == 'a' || conversion == 'A') return substr<0, i - 1, true>(fmt).s + strprintf(makeDirective<fmt, conversion, i, iAfterPrecision, 0>().s, convert<double, false>(std::forward<Arg>(arg), "double", argumentIndex)) + format_s<substr<iAfterPrecision + 1>(fmt), 0, argumentIndex + 1>(std::forward<Args>(args)...);
+			else if constexpr (conversion == 'p') return substr<0, i - 1, true>(fmt).s + strprintf(makeDirective<fmt, conversion, i, iAfterPrecision, 0>().s, convert<const void *, false>(std::forward<Arg>(arg), "pointer", argumentIndex)) + format_s<substr<iAfterPrecision + 1>(fmt), 0, argumentIndex + 1>(std::forward<Args>(args)...);
+			else if constexpr (conversion == 's')
+			{
+				const auto& string = convert<string_or_string_view<remove_cvref_t<Arg>>, false>(std::forward<Arg>(arg), "string", argumentIndex);
+				return substr<0, i - 1, true>(fmt).s + strprintf((str{"%."}.s + std::to_string(determineStringPrecision<havePrecision, fmt, iAfterFieldWidth, iAfterPrecision>(string)) + 's').c_str(), string.data()) + format_s<substr<iAfterPrecision + 1>(fmt), 0, argumentIndex + 1>(std::forward<Args>(args)...);
+			}
+			else
+			{
+				static_assert(fmt.size == 0, "Unknown conversion specifier!");
+				throw FormatException{std::string{"Unknown conversion specifier: \""} + conversion + "\""};
+			}
+		}
+		else return format_s<fmt, i + 1, argumentIndex>(std::forward<Arg>(arg), std::forward<Args>(args)...);
+	}
+}
+
+template<auto fmt, typename... Args>
+std::string format_s(Args &&...args)
+{
+	return detail::format_s<fmt, 0, 1>(std::forward<Args>(args)...);
+}
 }
\ No newline at end of file
diff --git a/main.cpp b/main.cpp
index d7fb862..bea2436 100644
--- a/main.cpp
+++ b/main.cpp
@@ -1,8 +1,8 @@
 #include "cxxformat.hpp"
 #include <array>
+#include <utility>
 #include <iostream>
 
-
 template<size_t N, typename T>
 struct format::FormatConvert<std::string, T[N], std::enable_if_t<!std::is_same_v<format::detail::remove_cvref_t<T>, char>>>
 {
@@ -42,8 +42,9 @@ struct format::AutoConversion<T[N], std::enable_if_t<!std::is_same_v<format::det
 
 int main(int argc, char *argv[])
 {
-	std::cout << format::format("%v%v%v%v%v", 'H', 'a', 'l', 'l', 'o') << std::endl;
 	const std::array<int, 5> array[] = {std::array{1, 2, 3, 4, 5}, std::array{1, 2, 3, 4, 5}, std::array{1, 2, 3, 4, 5}, std::array{1, 2, 3, 4, 5}, std::array{1, 2, 3, 4, 5}};
+	std::cout << format::format_s<format::str{"Hello %s: %d %03.5f %V"}>("World", 7, 3.5, &array) << std::endl;
+	std::cout << format::format("%v%v%v%v%v", 'H', 'e', 'l', 'l', 'o') << std::endl;
 	std::cout << format::format("%V", &array) << std::endl;
 	std::cout << format::format("%s", std::array{1, 2, 3, 4, 5}) << std::endl;
 	std::cout << format::format("Hello %v: %-7v %v", "World", 3.5, 5) << std::endl;