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#pragma once
#include "format_arg.h"
#include <util/generic/strbuf.h>
#include <algorithm>
#include <array>
#include <string_view>
namespace NYT::NDetail {
////////////////////////////////////////////////////////////////////////////////
struct TFormatAnalyser
{
public:
using TMarkerLocation = std::tuple<int, int>;
// NB(arkady-e1ppa): Location is considered invalid (e.g. not filled)
// if get<0> == get<1> == 0.
template <class... TArgs>
using TMarkerLocations = std::array<TMarkerLocation, sizeof...(TArgs)>;
// NB(arkady-e1ppa): We can't cover all of them since that would require
// dynamic storage for their coordinates and we do not have
// constexpr context large enough to deallocate dynamic memory at the
// correct time. Thus we store first 5 position and scanning afterwards
// is pessimized. |-1| is for no position at all.
// |-2| is used to imply runtime format.
using TEscapeLocations = std::array<int, 5>;
// TODO(arkady-e1ppa): Until clang-19 consteval functions
// defined out of line produce symbols in rare cases
// causing linker to crash.
template <class... TArgs>
static consteval auto AnalyzeFormat(std::string_view fmt)
{
return DoAnalyzeFormat<TArgs...>(fmt);
}
private:
static consteval bool Contains(std::string_view sv, char symbol)
{
return sv.find(symbol) != std::string_view::npos;
}
struct TSpecifiers
{
std::string_view Conversion;
std::string_view Flags;
};
template <class TArg>
static consteval auto GetSpecifiers()
{
return TSpecifiers{
.Conversion = std::string_view{
std::data(TFormatArg<TArg>::ConversionSpecifiers),
std::size(TFormatArg<TArg>::ConversionSpecifiers)},
.Flags = std::string_view{
std::data(TFormatArg<TArg>::FlagSpecifiers),
std::size(TFormatArg<TArg>::FlagSpecifiers)},
};
}
static constexpr char IntroductorySymbol = '%';
template <class... TArgs>
static consteval auto DoAnalyzeFormat(std::string_view format)
{
std::array<TSpecifiers, sizeof...(TArgs)> specifiers{GetSpecifiers<TArgs>()...};
TMarkerLocations<TArgs...> markerLocations = {};
TEscapeLocations escapeLocations = {};
std::ranges::fill(escapeLocations, -1);
int escapesCount = 0;
int markerCount = 0;
int currentMarkerStart = -1;
for (int index = 0; index < std::ssize(format); ++index) {
auto symbol = format[index];
// Parse verbatim text.
if (currentMarkerStart == -1) {
if (symbol == IntroductorySymbol) {
// Marker maybe begins.
currentMarkerStart = index;
}
continue;
}
// NB: We check for %% first since
// in order to verify if symbol is a specifier
// we need markerCount to be within range of our
// specifier array.
if (symbol == IntroductorySymbol) {
if (currentMarkerStart + 1 != index) {
// '%a% detected'
throw "You may not terminate flag sequence other than %% with \'%\' symbol";
}
// '%%' detected --- skip
if (escapesCount < std::ssize(escapeLocations)) {
escapeLocations[escapesCount] = currentMarkerStart;
++escapesCount;
}
currentMarkerStart = -1;
continue;
}
// We are inside of marker.
if (markerCount == std::ssize(markerLocations)) {
// Too many markers
throw "Number of arguments supplied to format is smaller than the number of flag sequences";
}
if (Contains(specifiers[markerCount].Conversion, symbol)) {
// Marker has finished.
markerLocations[markerCount]
= std::tuple{currentMarkerStart, index + 1};
currentMarkerStart = -1;
++markerCount;
continue;
}
if (!Contains(specifiers[markerCount].Flags, symbol)) {
throw "Symbol is not a valid flag specifier; See FlagSpecifiers";
}
}
if (currentMarkerStart != -1) {
// Runaway marker.
throw "Unterminated flag sequence detected; Use \'%%\' to type plain %";
}
if (markerCount < std::ssize(markerLocations)) {
// Missing markers.
throw "Number of arguments supplied to format is greater than the number of flag sequences";
}
// TODO(arkady-e1ppa): Consider per-type verification
// of markers.
return std::tuple(markerLocations, escapeLocations);
}
};
////////////////////////////////////////////////////////////////////////////////
} // namespace NYT::NDetail
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