Know issues
We would like to introduce an incremental parsing phase (see tree-sitter).
Because, when you have tokens (which may be as simple as words) or an AST,
completion / suggestion / highlting / validation become easy.
So we need to send events to a lexer/parser, update Document accordingly.
And fix Completer / Hinter / Highlighter API such as they have access to Document.
See lex_document.
Currently, performance is poor because, most of the time, we refresh the whole line (and prompt). We would like to transform events on prompt/line/hint into partial repaint.
See termwiz design (Surface).
We would like to support user defined actions that interact nicely with undo manager and kill-ring. To do so, we need to refactor current key event dispatch.
See replxx design (ACTION_RESULT, action_trait_t).