3 files changed, 66 insertions, 14 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 1056a763..e1642da2 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -30,5 +30,4 @@ else()
 endif()
 
 find_package(Microsoft.GSL CONFIG REQUIRED)
-find_package(fmt CONFIG REQUIRED)
-target_link_libraries(cru_base PUBLIC Microsoft.GSL::GSL fmt::fmt)
+target_link_libraries(cru_base PUBLIC Microsoft.GSL::GSL)
diff --git a/src/common/Logger.cpp b/src/common/Logger.cpp
index af1dd692..e77e8a85 100644
--- a/src/common/Logger.cpp
+++ b/src/common/Logger.cpp
@@ -30,7 +30,7 @@ void Logger::RemoveSource(ILogSource *source) {
 }
 
 namespace {
-std::u16string_view LogLevelToString(LogLevel level) {
+String LogLevelToString(LogLevel level) {
   switch (level) {
     case LogLevel::Debug:
       return u"DEBUG";
@@ -45,36 +45,35 @@ std::u16string_view LogLevelToString(LogLevel level) {
   }
 }
 
-std::u16string GetLogTime() {
+String GetLogTime() {
   auto time = std::time(nullptr);
   auto calendar = std::localtime(&time);
-  return fmt::format(u"{}:{}:{}", calendar->tm_hour, calendar->tm_min,
-                     calendar->tm_sec);
+  return Format(u"{}:{}:{}", calendar->tm_hour, calendar->tm_min,
+                calendar->tm_sec);
 }
 }  // namespace
 
-void Logger::Log(LogLevel level, std::u16string_view s) {
+void Logger::Log(LogLevel level, const String &message) {
 #ifndef CRU_DEBUG
   if (level == LogLevel::Debug) {
     return;
   }
 #endif
   for (const auto &source : sources_) {
-    source->Write(level, fmt::format(u"[{}] {}: {}\n", GetLogTime(),
-                                     LogLevelToString(level), s));
+    source->Write(level, Format(u"[{}] {}: {}\n", GetLogTime(),
+                                LogLevelToString(level), message));
   }
 }
 
-void Logger::Log(LogLevel level, std::u16string_view tag,
-                 std::u16string_view s) {
+void Logger::Log(LogLevel level, const String &tag, const String &message) {
 #ifndef CRU_DEBUG
   if (level == LogLevel::Debug) {
     return;
   }
 #endif
   for (const auto &source : sources_) {
-    source->Write(level, fmt::format(u"[{}] {} {}: {}\n", GetLogTime(),
-                                     LogLevelToString(level), tag, s));
+    source->Write(level, Format(u"[{}] {} {}: {}\n", GetLogTime(),
+                                LogLevelToString(level), tag, message));
   }
 }
 }  // namespace cru::log
diff --git a/src/common/String.cpp b/src/common/String.cpp
index e9acf984..94eb8f27 100644
--- a/src/common/String.cpp
+++ b/src/common/String.cpp
@@ -101,6 +101,10 @@ String::~String() {
   }
 }
 
+String::String(from_buffer_tag, std::uint16_t* buffer, Index size,
+               Index capacity)
+    : buffer_(buffer), size_(size), capacity_(capacity) {}
+
 void String::resize(Index new_size) {
   Expects(new_size >= 0);
 
@@ -137,7 +141,7 @@ void String::reserve(Index new_capacity) {
   }
 }
 
-String::iterator String::insert(const_iterator pos, std::uint16_t* str,
+String::iterator String::insert(const_iterator pos, const std::uint16_t* str,
                                 Index size) {
   Index new_size = size_ + size;
   if (new_size > capacity_) {
@@ -239,4 +243,54 @@ int String::Compare(const String& other) const {
   }
 }
 
+namespace details {
+std::vector<FormatToken> ParseToFormatTokenList(const String& str) {
+  std::vector<FormatToken> result;
+
+  auto push_char = [&result](std::uint16_t c) {
+    if (result.empty() || result.back().type == FormatTokenType::PlaceHolder) {
+      result.push_back(FormatToken{FormatTokenType::Text, String{}});
+    }
+    result.back().data.append(c);
+  };
+
+  bool last_is_left_bracket = false;
+  for (auto c : str) {
+    if (c == u'{') {
+      if (last_is_left_bracket) {
+        push_char(u'{');
+        last_is_left_bracket = false;
+      } else {
+        last_is_left_bracket = true;
+      }
+    } else if (c == u'}') {
+      if (last_is_left_bracket) {
+        result.push_back(FormatToken{FormatTokenType::PlaceHolder, String{}});
+      }
+      last_is_left_bracket = false;
+    } else {
+      if (last_is_left_bracket) {
+        push_char(u'{');
+      }
+      push_char(c);
+      last_is_left_bracket = false;
+    }
+  }
+  return result;
+}
+
+void FormatAppendFromFormatTokenList(
+    String& current, const std::vector<FormatToken>& format_token_list,
+    Index index) {
+  for (Index i = index; i < format_token_list.size(); i++) {
+    const auto& token = format_token_list[i];
+    if (token.type == FormatTokenType::PlaceHolder) {
+      current += u"{}";
+    } else {
+      current += token.data;
+    }
+  }
+}
+}  // namespace details
+
 }  // namespace cru