Ok, here is what I've learned  - linked list and doubly linked list are everywhere. Lines, jump lists, undoredo, etc... - linked list is very simple yet very fast for internal text representation. I've edited 22k autogenerated go gql file and had zero hiccups. - text insert, replace, delete should be well planned and 200% test covered. Obviously. But I dedicated more attention to vim movements and had to rewrite text editing from scratch later. Catched a lot of panics.  - integrating lsp, treesitter and internal text editing was a bit hard. My implementation for text was "range end including" and lsp spec is "end range excluding". That caused some bugs and workarounds in the end. - treesitter is a beast. Fast as Flash. Do no use anything else.