refactor: use source_location, not region_base*

toml/source_location.hpp

@@ -61,6 +61,21 @@ struct source_location
         }
     }
 
+    explicit source_location(const detail::region& reg)
+        : line_num_(static_cast<std::uint_least32_t>(std::stoul(reg.line_num()))),
+          column_num_(static_cast<std::uint_least32_t>(reg.before() + 1)),
+          region_size_(static_cast<std::uint_least32_t>(reg.size())),
+          file_name_(reg.name()),
+          line_str_ (reg.line())
+    {}
+    explicit source_location(const detail::location& loc)
+        : line_num_(static_cast<std::uint_least32_t>(std::stoul(loc.line_num()))),
+          column_num_(static_cast<std::uint_least32_t>(loc.before() + 1)),
+          region_size_(static_cast<std::uint_least32_t>(loc.size())),
+          file_name_(loc.name()),
+          line_str_ (loc.line())
+    {}
+
     ~source_location() = default;
     source_location(source_location const&) = default;
     source_location(source_location &&)     = default;
@@ -83,5 +98,112 @@ struct source_location
     std::string         line_str_;
 };
 
+namespace detail
+{
+
+// internal error message generation.
+inline std::string format_underline(const std::string& message,
+        const std::vector<std::pair<source_location, std::string>>& loc_com,
+        const std::vector<std::string>& helps = {},
+        const bool colorize = TOML11_ERROR_MESSAGE_COLORIZED)
+{
+    assert(!loc_com.empty());
+
+    const auto line_num_width = static_cast<int>(std::to_string(std::max_element(
+        loc_com.begin(), loc_com.end(),
+        [](std::pair<source_location, std::string> const& lhs,
+           std::pair<source_location, std::string> const& rhs)
+        {
+            return std::to_string(lhs.first.line()).size() <
+                   std::to_string(rhs.first.line()).size();
+        }
+    )->first.line()).size());
+
+    std::ostringstream retval;
+
+    if(colorize)
+    {
+        retval << color::colorize; // turn on ANSI color
+    }
+
+    // XXX
+    // Here, before `colorize` support, it does not output `[error]` prefix
+    // automatically. So some user may output it manually and this change may
+    // duplicate the prefix. To avoid it, check the first 7 characters and
+    // if it is "[error]", it removes that part from the message shown.
+    if(message.size() > 7 && message.substr(0, 7) == "[error]")
+    {
+        retval << color::bold << color::red << "[error]" << color::reset
+               << color::bold << message.substr(7) << color::reset << '\n';
+    }
+    else
+    {
+        retval << color::bold << color::red << "[error] " << color::reset
+               << color::bold << message << color::reset << '\n';
+    }
+
+    for(auto iter = loc_com.begin(); iter != loc_com.end(); ++iter)
+    {
+        // if the filenames are the same, print "..."
+        if(iter != loc_com.begin() &&
+           std::prev(iter)->first.file_name() == iter->first.file_name())
+        {
+            retval << color::bold << color::blue << "\n ...\n" << color::reset;
+        }
+        else // if filename differs, print " --> filename.toml"
+        {
+            if(iter != loc_com.begin()) {retval << '\n';}
+
+            retval << color::bold << color::blue << " --> " << color::reset
+                   << iter->first.file_name() << '\n';
+            // add one almost-empty line for readability
+            retval << make_string(static_cast<std::size_t>(line_num_width + 1), ' ')
+                   << color::bold << color::blue << " | "  << color::reset << '\n';
+        }
+        const source_location& loc = iter->first;
+        const std::string& comment = iter->second;
+
+        retval << ' ' << color::bold << color::blue << std::setw(line_num_width)
+               << std::right << loc.line() << " | "  << color::reset
+               << loc.line_str() << '\n';
+
+        retval << make_string(static_cast<std::size_t>(line_num_width + 1), ' ')
+               << color::bold << color::blue << " | " << color::reset
+               << make_string(loc.column()-1 /*1-origin*/, ' ');
+
+        if(loc.region() == 1)
+        {
+            // invalid
+            // ^------
+            retval << color::bold << color::red << "^---" << color::reset;
+        }
+        else
+        {
+            // invalid
+            // ~~~~~~~
+            const auto underline_len = (std::min)(
+                static_cast<std::size_t>(loc.region()), loc.line_str().size());
+            retval << color::bold << color::red
+                   << make_string(underline_len, '~') << color::reset;
+        }
+        retval << ' ';
+        retval << comment;
+    }
+
+    if(!helps.empty())
+    {
+        retval << '\n';
+        retval << make_string(static_cast<std::size_t>(line_num_width + 1), ' ');
+        retval << color::bold << color::blue << " | " << color::reset;
+        for(const auto& help : helps)
+        {
+            retval << color::bold << "\nHint: " << color::reset;
+            retval << help;
+        }
+    }
+    return retval.str();
+}
+
+} // detail
 } // toml
 #endif// TOML11_SOURCE_LOCATION_HPP