From 2caf1b3b91f6d56f420cec8bf752f9af26aa51af Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@meta.com>
Date: Sun, 21 Jan 2024 07:56:56 -0800
Subject: [PATCH] scan more

---
 test/scan.h | 47 +++++++++++++++++++++++++++++------------------
 1 file changed, 29 insertions(+), 18 deletions(-)

diff --git a/test/scan.h b/test/scan.h
index 19e9572d..59f41f77 100644
--- a/test/scan.h
+++ b/test/scan.h
@@ -8,6 +8,7 @@
 #include <array>
 #include <cassert>
 #include <climits>
+#include <tuple>
 
 #include "fmt/format.h"
 
@@ -549,6 +550,11 @@ struct scan_handler {
 
   void on_error(const char* message) { report_error(message); }
 };
+
+void vscan(detail::scan_buffer& buf, string_view fmt, scan_args args) {
+  auto h = detail::scan_handler(fmt, buf, args);
+  detail::parse_format_string<false>(fmt, h);
+}
 }  // namespace detail
 
 template <typename... T>
@@ -556,18 +562,22 @@ auto make_scan_args(T&... args) -> std::array<scan_arg, sizeof...(T)> {
   return {{args...}};
 }
 
-template <typename T> class scan_value {
+template <typename... T> class scan_data {
  private:
-  T value_;
+  std::tuple<T...> values_;
 
  public:
-  scan_value(T value) : value_(std::move(value)) {}
+  scan_data(T... values) : values_(std::move(values)...) {}
 
-  auto value() const -> const T& { return value_; }
+  auto value() const -> decltype(std::get<0>(values_)) {
+    return std::get<0>(values_);
+  }
 };
 
+class scan_error {};
+
 // A rudimentary version of std::expected for testing the API shape.
-template <typename T> class expected {
+template <typename T, typename E> class expected {
  private:
   T value_;
 
@@ -577,20 +587,21 @@ template <typename T> class expected {
   auto operator->() const -> const T* { return &value_; }
 };
 
-template <typename T> using scan_result = expected<scan_value<T>>;
+template <typename... T>
+using scan_result = expected<scan_data<T...>, scan_error>;
 
-void vscan(detail::scan_buffer& buf, string_view fmt, scan_args args) {
-  auto h = detail::scan_handler(fmt, buf, args);
-  detail::parse_format_string<false>(fmt, h);
+auto vscan(string_view input, string_view fmt, scan_args args)
+    -> string_view::iterator {
+  auto&& buf = detail::string_scan_buffer(input);
+  detail::vscan(buf, fmt, args);
+  return input.begin() + (buf.begin().base() - input.data());
 }
 
 // Scans the input and stores the results (in)to args.
 template <typename... T>
 auto scan_to(string_view input, string_view fmt, T&... args)
     -> string_view::iterator {
-  auto&& buf = detail::string_scan_buffer(input);
-  vscan(buf, fmt, make_scan_args(args...));
-  return input.begin() + (buf.begin().base() - input.data());
+  return vscan(input, fmt, make_scan_args(args...));
 }
 
 template <typename T>
@@ -598,22 +609,22 @@ auto scan(string_view input, string_view fmt) -> scan_result<T> {
   static_assert(std::is_same<remove_cvref_t<T>, T>::value, "");
   auto value = T();
   scan_to(input, fmt, value);
-  return scan_value<T>(std::move(value));
+  return scan_data<T>(std::move(value));
 }
 
-template <typename InputRange, typename... T,
-          FMT_ENABLE_IF(!std::is_convertible<InputRange, string_view>::value)>
-auto scan_to(InputRange&& input, string_view fmt, T&... args)
+template <typename Range, typename... T,
+          FMT_ENABLE_IF(!std::is_convertible<Range, string_view>::value)>
+auto scan_to(Range&& input, string_view fmt, T&... args)
     -> decltype(std::begin(input)) {
   auto it = std::begin(input);
-  vscan(get_buffer(it), fmt, make_scan_args(args...));
+  detail::vscan(get_buffer(it), fmt, make_scan_args(args...));
   return it;
 }
 
 template <typename... T>
 auto scan_to(FILE* f, string_view fmt, T&... args) -> bool {
   auto&& buf = detail::file_scan_buffer(f);
-  vscan(buf, fmt, make_scan_args(args...));
+  detail::vscan(buf, fmt, make_scan_args(args...));
   return buf.begin() != buf.end();
 }