Pretty sure LuaTeX or ConTeXt LMTX (an experimental LuaTeX fork) is a better choice for programmability. LuaTeX is the most recent TeX engine, and it is very pr

Pretty sure LuaTeX or ConTeXt LMTX (an experimental LuaTeX fork) is a better choice for programmability. LuaTeX is the most recent TeX engine, and it is very programmable using Lua (as in no TeX code required). I know, Lua sucks very much, but nonetheless the power that LuaTeX (and/or ConTeXt) offers is probably currently unmatched. (And don't forget that Lua has a C API, so it is possible to drive the TeX engine with C++ or Go or Rust or whatever.)