4 files changed, 75 insertions, 44 deletions
diff --git a/include/cru/common/Base.hpp b/include/cru/common/Base.hpp
index 409c2b0e..93d6f9a6 100644
--- a/include/cru/common/Base.hpp
+++ b/include/cru/common/Base.hpp
@@ -47,5 +47,5 @@ using Index = gsl::index;
 
 #define CRU_DEFINE_CLASS_LOG_TAG(tag) \
  private:                             \
-  constexpr static std::string_view log_tag = tag;
+  constexpr static std::u16string_view log_tag = tag;
 }  // namespace cru
diff --git a/include/cru/common/Logger.hpp b/include/cru/common/Logger.hpp
index f76e4626..f83ba8dc 100644
--- a/include/cru/common/Logger.hpp
+++ b/include/cru/common/Logger.hpp
@@ -15,30 +15,7 @@ enum class LogLevel { Debug, Info, Warn, Error };
 struct ILogSource : virtual Interface {
   // Write the string s. LogLevel is just a helper. It has no effect on the
   // content to write.
-  virtual void Write(LogLevel level, std::string_view s) = 0;
-};
-
-class StdioLogSource : public virtual ILogSource {
- public:
-  StdioLogSource() = default;
-
-  CRU_DELETE_COPY(StdioLogSource)
-  CRU_DELETE_MOVE(StdioLogSource)
-
-  ~StdioLogSource() override = default;
-
-  void Write(LogLevel level, std::string_view s) override {
-    // TODO: Emmm... Since it is buggy to use narrow char in UTF-8 on Windows. I
-    // think this implementation might be broken. (However, I didn't test it.)
-    // Maybe, I should detect Windows and use wide char (And I didn't test this
-    // either) or other more complicated implementation. Currently, I settled
-    // with this.
-    if (level == LogLevel::Error) {
-      std::cerr << s;
-    } else {
-      std::cout << s;
-    }
-  }
+  virtual void Write(LogLevel level, const std::u16string& s) = 0;
 };
 
 class Logger : public Object {
@@ -58,8 +35,8 @@ class Logger : public Object {
   void RemoveSource(ILogSource* source);
 
  public:
-  void Log(LogLevel level, std::string_view s);
-  void Log(LogLevel level, std::string_view tag, std::string_view s);
+  void Log(LogLevel level, std::u16string_view s);
+  void Log(LogLevel level, std::u16string_view tag, std::u16string_view s);
 
  public:
   std::list<std::unique_ptr<ILogSource>> sources_;
@@ -92,7 +69,7 @@ void Error(TArgs&&... args) {
 }
 
 template <typename... TArgs>
-void TagDebug([[maybe_unused]] std::string_view tag,
+void TagDebug([[maybe_unused]] std::u16string_view tag,
               [[maybe_unused]] TArgs&&... args) {
 #ifdef CRU_DEBUG
   Logger::GetInstance()->Log(LogLevel::Debug, tag,
@@ -101,19 +78,19 @@ void TagDebug([[maybe_unused]] std::string_view tag,
 }
 
 template <typename... TArgs>
-void TagInfo(std::string_view tag, TArgs&&... args) {
+void TagInfo(std::u16string_view tag, TArgs&&... args) {
   Logger::GetInstance()->Log(LogLevel::Info, tag,
                              fmt::format(std::forward<TArgs>(args)...));
 }
 
 template <typename... TArgs>
-void TagWarn(std::string_view tag, TArgs&&... args) {
+void TagWarn(std::u16string_view tag, TArgs&&... args) {
   Logger::GetInstance()->Log(LogLevel::Warn, tag,
                              fmt::format(std::forward<TArgs>(args)...));
 }
 
 template <typename... TArgs>
-void TagError(std::string_view tag, TArgs&&... args) {
+void TagError(std::u16string_view tag, TArgs&&... args) {
   Logger::GetInstance()->Log(LogLevel::Error, tag,
                              fmt::format(std::forward<TArgs>(args)...));
 }
diff --git a/include/cru/common/PreConfig.hpp b/include/cru/common/PreConfig.hpp
index 4bccef1d..802f17f8 100644
--- a/include/cru/common/PreConfig.hpp
+++ b/include/cru/common/PreConfig.hpp
@@ -6,3 +6,4 @@
 #endif
 
 #define _CRT_SECURE_NO_WARNINGS
+#define _SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING
diff --git a/include/cru/common/StringUtil.hpp b/include/cru/common/StringUtil.hpp
index a44ae6b4..714f1d49 100644
--- a/include/cru/common/StringUtil.hpp
+++ b/include/cru/common/StringUtil.hpp
@@ -3,37 +3,90 @@
 
 namespace cru {
 using CodePoint = std::int32_t;
-constexpr CodePoint k_code_point_end = -1;
+constexpr CodePoint k_invalid_code_point = -1;
 
 class TextEncodeException : public std::runtime_error {
  public:
   using runtime_error::runtime_error;
 };
 
-class Utf8Iterator : public Object {
+inline bool IsSurrogatePair(char16_t c) { return c >= 0xD800 && c <= 0xDFFF; }
+
+inline bool IsSurrogatePairLeading(char16_t c) {
+  return c >= 0xD800 && c <= 0xDBFF;
+}
+
+inline bool IsSurrogatePairTrailing(char16_t c) {
+  return c >= 0xDC00 && c <= 0xDFFF;
+}
+
+class Utf16Iterator : public Object {
  public:
-  explicit Utf8Iterator(const std::string_view& string) : string_(string) {}
-  Utf8Iterator(const std::string_view& string, Index position)
-      : string_(string), position_(position) {}
+  explicit Utf16Iterator(std::u16string_view string)
+      : string_(std::move(string)) {}
+  Utf16Iterator(std::u16string_view string, Index position)
+      : string_(std::move(string)), position_(position) {}
 
-  CRU_DEFAULT_COPY(Utf8Iterator)
-  CRU_DEFAULT_MOVE(Utf8Iterator)
+  CRU_DEFAULT_COPY(Utf16Iterator)
+  CRU_DEFAULT_MOVE(Utf16Iterator)
 
-  ~Utf8Iterator() = default;
+  ~Utf16Iterator() = default;
 
  public:
-  void SetToHead() { position_ = 0; }
+  void SetPositionToHead() { position_ = 0; }
   void SetPosition(Index position) { position_ = position; }
 
-  // Advance current position and get next code point. Return k_code_point_end
-  // if there is no next code unit(point). Throw TextEncodeException if decoding
-  // fails.
+  // Backward current position and get previous code point. Return
+  // k_invalid_code_point if reach head. Throw TextEncodeException if encounter
+  // encoding problem.
+  CodePoint Previous();
+
+  // Advance current position and get next code point. Return
+  // k_invalid_code_point if reach tail. Throw TextEncodeException if encounter
+  // encoding problem.
   CodePoint Next();
 
   Index CurrentPosition() const { return this->position_; }
 
  private:
-  std::string_view string_;
+  std::u16string_view string_;
   Index position_ = 0;
 };
+
+Index PreviousIndex(std::u16string_view string, Index current);
+Index NextIndex(std::u16string_view string, Index current);
+
+std::string ToUtf8(const std::u16string& s);
+inline std::string ToUtf8(std::u16string_view s) {
+  return ToUtf8(std::u16string{s});
+}
+
+// class Utf8Iterator : public Object {
+//  public:
+//   explicit Utf8Iterator(const std::string_view& string) : string_(string) {}
+//   Utf8Iterator(const std::string_view& string, Index position)
+//       : string_(string), position_(position) {}
+
+//   CRU_DEFAULT_COPY(Utf8Iterator)
+//   CRU_DEFAULT_MOVE(Utf8Iterator)
+
+//   ~Utf8Iterator() = default;
+
+//  public:
+//   void SetToHead() { position_ = 0; }
+//   void SetPosition(Index position) { position_ = position; }
+
+//   // Advance current position and get next code point. Return
+//   k_invalid_code_point
+//   // if there is no next code unit(point). Throw TextEncodeException if
+//   decoding
+//   // fails.
+//   CodePoint Next();
+
+//   Index CurrentPosition() const { return this->position_; }
+
+//  private:
+//   std::string_view string_;
+//   Index position_ = 0;
+// };
 }  // namespace cru