The project uses xmake (https://xmake.io/), see https://xmake.io/#/getting_started on how to set it up.
It also depends on ANTLR, which is included in the repo.
ANTLR has to be built using CMake and installed into the antlr4-cpp-runtime-4.9.2-source/install directory by invoking the INSTALL CMake target.
The proejct can then be built by simply invoking xmake and can be run using the current directory as working directory by running xmake run -w ..
All of the code is in src/ and the ANTLR grammar file is Toc.g4.
The C++ code generated from the grammar is in gen/ and is up-to-date, but can be regenerated by running java -jar antlr-4.9.2-complete.jar -Dlanguage=Cpp -no-listener -o gen Toc.g4.