babashka autocomplete (semi-working) idea

autocomplete.clj

#!/usr/bin/env bash

;; From https://github.com/remkop/picocli/blob/master/src/test/resources/picocompletion-demo-help_completion.bash#L45
;; Copy following in terminal (bash / zsh)
;
; if [ -n "$BASH_VERSION" ]; then
;   # Enable programmable completion facilities when using bash (see [3])
;   shopt -s progcomp
; elif [ -n "$ZSH_VERSION" ]; then
;   # Make alias a distinct command for completion purposes when using zsh (see [4])
;   setopt COMPLETE_ALIASES
;   alias compopt=complete
;
;   # Enable bash completion in zsh (see [7])
;   autoload -U +X compinit && compinit
;   autoload -U +X bashcompinit && bashcompinit
; fi
;
; complete -C "bb $PWD/complete.bb" -o default bb-complete


(require '[babashka.tasks :refer [shell]])

;; Following could be generated based on tasks in bb.edn or could be part of it
(def tree
  '{:opts #{--a --c}
    :cmds {aa {:cmd (println "a")
               :opts #{--foo}}
           aaa {:cmd (println "a")
                :opts #{--foo}}
           bb {:opts #{--bar}
               :cmds
               {sub1
                {:opts #{a}}}}
           }})


(if-let [args (or (some-> (System/getenv "COMP_LINE")
                          (clojure.string/split #" ")
                          rest) ;; FIXME Poor man cmd parsing here
                  (and (= (first *command-line-args*) "--autocomplete")
                       (rest *command-line-args*)))]
  (do
    (loop [[arg & left-args] (map symbol args)
           branch (:cmds tree)
           left-opts (:opts tree)]
      (or (and left-args
               (do
                 (if-let [next-branch (get branch arg)]
                   (recur left-args (:cmds next-branch) (:opts next-branch))
                   (if (get left-opts arg)
                     (recur left-args branch (disj left-opts arg))
                     nil ;; cannot autocomplete
                     )
                   )))
          ;; No need to look further present all options and leave it to complete
          (let [arg (str arg)
                current-opts (-> (into #{} (map str (concat (keys branch) left-opts)))
                                 (disj arg))]
            (println (clojure.string/join "\n" current-opts))))))

  (println "Normal execution"))