Add: Basic autocompletion on tab for console commands (#12163)

src/autocompletion.h

@@ -0,0 +1,46 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD 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, version 2.
+ * OpenTTD 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 OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file autocompletion.h Generic auto-completion engine. */
+
+#ifndef AUTOCOMPLETION_H
+#define AUTOCOMPLETION_H
+
+#include "textbuf_type.h"
+
+class AutoCompletion {
+protected:
+	Textbuf *textbuf;
+
+private:
+	std::string              initial_buf; ///< Value of text buffer when we started current suggestion session.
+
+	std::string_view         prefix;      ///< Prefix of the text before the last space.
+	std::string_view         query;       ///< Last token of the text. This is used to based the suggestions on.
+
+	std::vector<std::string> suggestions;
+	size_t                   current_suggestion_index;
+
+public:
+	AutoCompletion(Textbuf *textbuf) : textbuf(textbuf)
+	{
+		this->Reset();
+	}
+	virtual ~AutoCompletion() = default;
+
+	// Returns true the textbuf was updated.
+	bool AutoComplete();
+	void Reset();
+
+private:
+	void InitSuggestions(std::string_view text);
+
+	virtual std::vector<std::string> GetSuggestions(std::string_view prefix, std::string_view query) = 0;
+	virtual void ApplySuggestion(std::string_view prefix, std::string_view suggestion) = 0;
+};
+
+#endif /* AUTOCOMPLETION_H */