utils: implement language-detector

A thing wrapper around CLD2 with which we can detect the language of an
e-mail message.

lib/utils/mu-lang-detector.hh

@@ -0,0 +1,46 @@
+/*
+** Copyright (C) 2023 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+**
+** This program is free software; you can redistribute it and/or modify it
+** under the terms of the GNU General Public License as published by the
+** Free Software Foundation; either version 3, or (at your option) any
+** later version.
+**
+** This program is distributed in the hope that it will be useful,
+** but WITHOUT ANY WARRANTY; without even the implied warranty of
+** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+** GNU General Public License for more details.
+**
+** You should have received a copy of the GNU General Public License
+** along with this program; if not, write to the Free Software Foundation,
+** Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+**
+*/
+
+#ifndef MU_LANG_DETECTOR_HH__
+#define MU_LANG_DETECTOR_HH__
+
+#include <string>
+#include "mu-option.hh"
+
+namespace Mu {
+
+struct Language {
+	const char *name;	/**< Language name, e.g. "Dutch" */
+	const char *code;	/**< Language code, e.g. "nl" */
+};
+
+/**
+ * Detect the language of text
+ *
+ * @param txt some text (UTF-8)
+ *
+ * @return either a Language or nothing; the latter
+ * also if we cannot not reliably determine a single language
+ */
+Option<Language> detect_language(const std::string& txt);
+
+} // namespace Mu
+
+
+#endif /* MU_LANG_DETECTOR_HH__ */