Simplify runtime implementation

1 files changed, 66 insertions, 54 deletions

diff --git a/include/cxxformat/runtime.hpp b/include/cxxformat/runtime.hpp
index 23f2b96..3bfe7fe 100644
--- a/include/cxxformat/runtime.hpp
+++ b/include/cxxformat/runtime.hpp
@@ -15,15 +15,43 @@ namespace format {
 			std::vector<std::variant<std::string, format_specifier>> parts;
 			std::size_t argCount;
 
+			template<typename Out>
+			struct argument_formatter {
+				virtual void format(const Out& out, format_specifier spec, optional_int<std::size_t> minWidth, optional_int<std::size_t> precision) = 0;
+				virtual void conversionSupported(format_specifier spec) = 0;
+				virtual ~argument_formatter() = default;
+			};
+
+			template<typename Out, typename Arg>
+			class argument_formatter_for : public argument_formatter<Out> {
+				Arg&& arg;
+
+				using formatter = formatter_with_fallback<std::decay_t<Arg>>;
+
+			public:
+				argument_formatter_for(Arg&& arg) : arg{std::forward<Arg>(arg)} {}
+
+				void format(const Out& out, format_specifier spec, optional_int<std::size_t> minWidth, optional_int<std::size_t> precision) override
+				{
+					formatter::format(out, arg, spec, minWidth, precision);
+				}
+
+				void conversionSupported(format_specifier spec) override
+				{
+					formatter::conversionSupported(spec);
+				}
+			};
+
 		public:
 			format_template(std::vector<std::variant<std::string, format_specifier>>&& parts, std::size_t argCount) noexcept : parts{std::move(parts)}, argCount{argCount} {}
 
 			template<format_output_compatible Output, typename... Args> requires (has_some_formatter<std::decay_t<Args>> && ...)
 			void operator()(Output&& output, Args&&... args) const
 			{
-				checkArgCount(sizeof...(Args));
+				constexpr auto passedArgCount = sizeof...(Args);
+				checkArgCount(passedArgCount);
 
-				std::array<optional_int<std::size_t>, sizeof...(Args)> indexArgs{[]<typename Arg>(Arg&& arg) constexpr -> optional_int<std::size_t> {
+				std::array<optional_int<std::size_t>, passedArgCount> indexArgs{[]<typename Arg>(Arg&& arg) constexpr -> optional_int<std::size_t> {
 					if constexpr (std::unsigned_integral<Arg> && sizeof(Arg) <= sizeof(std::size_t))
 					{
 						return static_cast<std::size_t>(arg);
@@ -34,69 +62,53 @@ namespace format {
 					}
 				}(std::forward<Args>(args))...};
 
-				const auto checkPart = [&args..., &indexArgs]<std::size_t... indices>(std::index_sequence<indices...>)
-				{
-					return [&args..., &indexArgs](format_specifier spec)
-					{
-						([spec, &indexArgs]<typename Arg>(Arg&&, std::size_t index)
-						{
-							if (index == spec.argIndex)
-							{
-								if (spec.flags.widthAsArg)
-								{
-									if (!indexArgs[*spec.minWidth])
-									{
-										throw std::invalid_argument{"Width argument must be an unsigned integral at most as big as std::size_t"};
-									}
-								}
-								if (spec.flags.precisionAsArg)
-								{
-									if (!indexArgs[*spec.precision])
-									{
-										throw std::invalid_argument{"Precision argument must be an unsigned integral at most as big as std::size_t"};
-									}
-								}
-								formatter_with_fallback<std::decay_t<Arg>>::conversionSupported(spec);
-							}
-						}(std::forward<Args>(args), indices), ...);
-					};
-				}(std::make_index_sequence<sizeof...(Args)>());
+				const auto out = make_output(std::forward<Output>(output));
+				using Out = decltype(out);
+
+				std::array<std::unique_ptr<argument_formatter<Out>>, passedArgCount> argFormatters{[]<typename Arg>(Arg&& arg) {
+					return std::unique_ptr<argument_formatter<Out>>{new argument_formatter_for<Out, Arg>{std::forward<Arg>(arg)}};
+				}(std::forward<Args>(args))...};
 
 				for (const auto& part : parts)
 				{
 					if (std::holds_alternative<format_specifier>(part))
 					{
-						checkPart(std::get<format_specifier>(part));
+						const auto spec = std::get<format_specifier>(part);
+						if (spec.flags.widthAsArg)
+						{
+							if (!indexArgs[*spec.minWidth])
+							{
+								throw std::invalid_argument{"Width argument must be an unsigned integral at most as big as std::size_t"};
+							}
+						}
+						if (spec.flags.precisionAsArg)
+						{
+							if (!indexArgs[*spec.precision])
+							{
+								throw std::invalid_argument{"Precision argument must be an unsigned integral at most as big as std::size_t"};
+							}
+						}
+						argFormatters[spec.argIndex]->conversionSupported(spec);
 					}
 				}
 
-				const auto out = make_output(std::forward<Output>(output));
 				const overloaded_callable visitor{
-					[&args..., &out, &indexArgs]<std::size_t... indices>(std::index_sequence<indices...>)
+					[&out, &indexArgs, &argFormatters](format_specifier spec)
 					{
-						return [&args..., &out, &indexArgs](format_specifier spec)
+						optional_int<std::size_t> minWidth = spec.minWidth;
+						if (spec.flags.widthAsArg)
 						{
-							([&out, spec, &indexArgs]<typename Arg>(Arg&& arg, std::size_t index)
-							{
-								if (index == spec.argIndex)
-								{
-									optional_int<std::size_t> minWidth = spec.minWidth;
-									if (spec.flags.widthAsArg)
-									{
-										minWidth = indexArgs[*minWidth];
-										assert(minWidth);
-									}
-									optional_int<std::size_t> precision = spec.precision;
-									if (spec.flags.precisionAsArg)
-									{
-										precision = indexArgs[*precision];
-										assert(precision);
-									}
-									return formatter_with_fallback<std::decay_t<Arg>>::format(out, std::forward<Arg>(arg), spec, minWidth, precision);
-								}
-							}(std::forward<Args>(args), indices), ...);
-						};
-					}(std::make_index_sequence<sizeof...(Args)>()),
+							minWidth = indexArgs[*minWidth];
+							assert(minWidth);
+						}
+						optional_int<std::size_t> precision = spec.precision;
+						if (spec.flags.precisionAsArg)
+						{
+							precision = indexArgs[*precision];
+							assert(precision);
+						}
+						return argFormatters[spec.argIndex]->format(out, spec, minWidth, precision);
+					},
 					[&out](std::string text) { out(text); }
 				};
 				for (const auto& part : parts)