input_utils.py

   1 #!/usr/bin/env python3
   2
   3 # © Copyright 2021-2022, Scott Gasch
   4
   5 """Utilities related to user input."""
   6
   7 import logging
   8 import signal
   9 import sys
  10 from typing import List
  11
  12 import readchar  # type: ignore
  13
  14 import exceptions
  15
  16 logger = logging.getLogger(__file__)
  17
  18
  19 def single_keystroke_response(
  20     valid_responses: List[str],
  21     *,
  22     prompt: str = None,
  23     default_response: str = None,
  24     timeout_seconds: int = None,
  25 ) -> str:
  26     """Get a single keystroke response to a prompt."""
  27
  28     def _handle_timeout(signum, frame) -> None:
  29         raise exceptions.TimeoutError()
  30
  31     def _single_keystroke_response_internal(
  32         valid_responses: List[str], timeout_seconds=None
  33     ) -> str:
  34         os_special_keystrokes = [3, 26]  # ^C, ^Z
  35         if timeout_seconds is not None:
  36             signal.signal(signal.SIGALRM, _handle_timeout)
  37             signal.alarm(timeout_seconds)
  38
  39         try:
  40             while True:
  41                 response = readchar.readchar()
  42                 logger.debug('Keystroke: 0x%x', ord(response))
  43                 if response in valid_responses:
  44                     break
  45                 if ord(response) in os_special_keystrokes:
  46                     break
  47             return response
  48         finally:
  49             if timeout_seconds is not None:
  50                 signal.alarm(0)
  51
  52     if prompt is not None:
  53         print(prompt, end="")
  54         sys.stdout.flush()
  55     try:
  56         response = _single_keystroke_response_internal(valid_responses, timeout_seconds)
  57         if ord(response) == 3:
  58             raise KeyboardInterrupt('User pressed ^C in input_utils.')
  59
  60     except exceptions.TimeoutError:
  61         if default_response is not None:
  62             response = default_response
  63     if prompt is not None:
  64         print(response)
  65     return response
  66
  67
  68 def yn_response(prompt: str = None, *, timeout_seconds=None) -> str:
  69     """Get a Y/N response to a prompt."""
  70
  71     return single_keystroke_response(
  72         ["y", "n", "Y", "N"], prompt=prompt, timeout_seconds=timeout_seconds
  73     ).lower()
  74
  75
  76 def keystroke_helper() -> None:
  77     """Misc util to watch keystrokes and report what they were."""
  78
  79     print("Watching for keystrokes; ^C to quit.")
  80     while True:
  81         key = readchar.readkey()
  82         if len(key) == 1:
  83             print(f'That was "{key}" ({ord(key)}).')
  84             if ord(key) == 3:
  85                 return
  86         else:
  87             print(f'That was sequence "{key}" (', end="")
  88             for _ in key:
  89                 print(f" {ord(_)} ", end="")
  90             print(")")