1 files changed, 108 insertions, 0 deletions
diff --git a/archived/projt-launcher/launcher/launch/LaunchVariableExpander.cpp b/archived/projt-launcher/launcher/launch/LaunchVariableExpander.cpp
new file mode 100644
index 0000000000..175b003115
--- /dev/null
+++ b/archived/projt-launcher/launcher/launch/LaunchVariableExpander.cpp
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-3.0-only
+// SPDX-FileCopyrightText: 2026 Project Tick
+// SPDX-FileContributor: Project Tick Team
+/*
+ *  ProjT Launcher - Minecraft Launcher
+ *  Copyright (C) 2026 Project Tick
+ *
+ *  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, version 3.
+ *
+ *  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.
+ */
+
+#include "LaunchVariableExpander.hpp"
+
+namespace projt::launch
+{
+	QString LaunchVariableExpander::expand(const QString& input, const QProcessEnvironment& env) const
+	{
+		QString output = input;
+
+		enum class Mode
+		{
+			Idle,
+			Sigil,
+			Name,
+			Brace
+		};
+
+		Mode mode	   = Mode::Idle;
+		int tokenStart = -1;
+
+		for (int idx = 0; idx < output.length();)
+		{
+			const QChar c = output.at(idx++);
+			switch (mode)
+			{
+				case Mode::Idle:
+					if (c == '$')
+					{
+						mode = Mode::Sigil;
+					}
+					break;
+				case Mode::Sigil:
+					if (c == '{')
+					{
+						mode	   = Mode::Brace;
+						tokenStart = idx;
+					}
+					else if (c.isLetterOrNumber() || c == '_')
+					{
+						mode	   = Mode::Name;
+						tokenStart = idx - 1;
+					}
+					else
+					{
+						mode = Mode::Idle;
+					}
+					break;
+				case Mode::Brace:
+					if (c == '}')
+					{
+						const auto key	 = output.mid(tokenStart, idx - 1 - tokenStart);
+						const auto value = env.value(key, "");
+						if (!value.isEmpty())
+						{
+							output.replace(tokenStart - 2, idx - tokenStart + 2, value);
+							idx = tokenStart - 2 + value.length();
+						}
+						mode = Mode::Idle;
+					}
+					break;
+				case Mode::Name:
+					if (!c.isLetterOrNumber() && c != '_')
+					{
+						const auto key	 = output.mid(tokenStart, idx - tokenStart - 1);
+						const auto value = env.value(key, "");
+						if (!value.isEmpty())
+						{
+							output.replace(tokenStart - 1, idx - tokenStart, value);
+							idx = tokenStart - 1 + value.length();
+						}
+						mode = Mode::Idle;
+					}
+					break;
+			}
+		}
+
+		if (mode == Mode::Name)
+		{
+			const auto value = env.value(output.mid(tokenStart), "");
+			if (!value.isEmpty())
+			{
+				output.replace(tokenStart - 1, output.length() - tokenStart + 1, value);
+			}
+		}
+
+		return output;
+	}
+} // namespace projt::launch