python: recursive command line completion

completion.py

#! /usr/bin/env python3
# -*- coding: utf-8 -*-

"""

  USE UNDER YOUR OWN RESPONSIBILITY!!
  
  IMPORTANT: options with sub-levels MUST end with spaces!!!

"""

import logging
import readline


def completer(text, state):
    """ Adapted from here: https://pymotw.com/2/readline/ """
    global current_candidates

    places = [ 'a', 'aa', 'ab', 'b', 'z', ]
    stores = { 'a ': [], 'aa ': [], 'ab ': places, 'ac ': places, 'v ': [], 'e ': places, }
    options = {
        '#go ':
            stores,
        '#goto ':
            places,
        '#other ':
            [ 'a', 'b', 'bo', 'ca', 'co', 'ee', 'eep', 'r', 'g', 'c', 'l', ]
    }

    if state == 0:
        # This is the first time for this text, so build a match list.

        origline = readline.get_line_buffer()
        begin = readline.get_begidx()
        end = readline.get_endidx()
        being_completed = origline[begin:end]
        words = origline.split()

        if not words:
            current_candidates = sorted(options.keys())
        else:
            try:
                if begin == 0:
                    # first word
                    candidates = options.keys()
                else:
                    candidates = options
                    # later word
                    for prev in words:
                        if prev in candidates and not origline.endswith(prev):
                            candidates = candidates[prev]
                            break
                        elif prev + ' ' in candidates and prev + ' ' in origline:
                            candidates = candidates[prev + ' ']

                if type(candidates) == dict:
                    candidates = list(candidates.keys())

                if being_completed:
                    # match options with portion of input
                    # being completed
                    current_candidates = [w for w in candidates if w.startswith(being_completed)]
                else:
                    # matching empty string so use all candidates
                    current_candidates = candidates

            except (KeyError, IndexError):
                current_candidates = []

    try:
        response = current_candidates[state]
    except IndexError:
        response = None
    return response


if __name__ == '__main__':

    # Prepare logger
    logging.getLogger(None).setLevel(logging.DEBUG)
    logging.basicConfig()

    # Setup command completion
    # Register our completer function
    current_candidates = []
    readline.set_completer_delims(' ')
    readline.set_completer(completer)
    readline.parse_and_bind('tab: complete')

    # Console reading loop
    while True:

        # Check for Ctrl-C; clean up and exit if found
        try:
            line = input('>> ').strip()
        except KeyboardInterrupt:
            break

        # Pass inputo to handler function (only if not empy)
        if line:
            print("-----> " + line)