baseimage-tutorial-framework/lib/tfw/components/terminal_commands.py

# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
# All Rights Reserved. See LICENSE file for details.

import logging
from abc import ABC
from re import match
from shlex import split

LOG = logging.getLogger(__name__)


class TerminalCommands(ABC):
    # pylint: disable=anomalous-backslash-in-string
    """
    A class you can use to define hooks for terminal commands. This means that you can
    have python code executed when the user enters a specific command to the terminal on
    our frontend.

    To receive events you need to subscribe TerminalCommand.callback to a HistoryMonitor
    instance.

    Inherit from this class and define methods which start with "command\_". When the user
    executes the command specified after the underscore, your method will be invoked. All
    such commands must expect the parameter \*args which will contain the arguments of the
    command.

    For example to define a method that runs when someone starts vim in the terminal
    you have to define a method like: "def command_vim(self, \*args)"

    You can also use this class to create new commands similarly.
    """
    def __init__(self, bashrc=None):
        self._command_method_regex = r'^command_(.+)$'
        self.command_implemetations = self._build_command_to_implementation_dict()
        if bashrc is not None:
            self._setup_bashrc_aliases(bashrc)

    def _build_command_to_implementation_dict(self):
        return {
            self._parse_command_name(fun): getattr(self, fun)
            for fun in dir(self)
            if callable(getattr(self, fun))
            and self._is_command_implementation(fun)
        }

    def _setup_bashrc_aliases(self, bashrc):
        with open(bashrc, 'a') as ofile:
            alias_template = 'type {0} &> /dev/null || alias {0}="{0} &> /dev/null"\n'
            for command in self.command_implemetations.keys():
                ofile.write(alias_template.format(command))

    def _is_command_implementation(self, method_name):
        return bool(self._match_command_regex(method_name))

    def _parse_command_name(self, method_name):
        try:
            return self._match_command_regex(method_name).groups()[0]
        except AttributeError:
            return ''

    def _match_command_regex(self, string):
        return match(self._command_method_regex, string)

    def callback(self, command):
        parts = split(command)
        command = parts[0]
        if command in self.command_implemetations.keys():
            try:
                self.command_implemetations[command](*parts[1:])
            except Exception: # pylint: disable=broad-except
                LOG.exception('Command "%s" failed:', command)