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

src/autocompletion.cpp

@@ -0,0 +1,66 @@
+/*
+ * 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.cpp Generic auto-completion engine. */
+
+#include "stdafx.h"
+
+#include "autocompletion.h"
+
+#include "console_internal.h"
+#include "town.h"
+#include "network/network_base.h"
+
+#include "safeguards.h"
+
+bool AutoCompletion::AutoComplete()
+{
+	// We are pressing TAB for the first time after reset.
+	if (this->suggestions.empty()) {
+		this->InitSuggestions(this->textbuf->buf);
+		if (this->suggestions.empty()) {
+			return false;
+		}
+		this->ApplySuggestion(prefix, suggestions[0]);
+		return true;
+	}
+
+	// We are pressing TAB again on the same text.
+	if (this->current_suggestion_index + 1 < this->suggestions.size()) {
+		this->ApplySuggestion(prefix, this->suggestions[++this->current_suggestion_index]);
+	} else {
+		// We are out of options, restore original text.
+		this->textbuf->Assign(initial_buf);
+		this->Reset();
+	}
+	return true;
+}
+
+void AutoCompletion::Reset()
+{
+	this->prefix = "";
+	this->query = "";
+	this->initial_buf.clear();
+	this->suggestions.clear();
+	this->current_suggestion_index = 0;
+}
+
+void AutoCompletion::InitSuggestions(std::string_view text)
+{
+	this->initial_buf = text;
+	size_t space_pos = this->initial_buf.find_last_of(' ');
+	this->query = this->initial_buf;
+	if (space_pos == std::string::npos) {
+		this->prefix = "";
+	} else {
+		this->prefix = this->query.substr(0, space_pos + 1);
+		this->query.remove_prefix(space_pos + 1);
+	}
+
+	this->suggestions = this->GetSuggestions(prefix, query);
+	this->current_suggestion_index = 0;
+}