#!/usr/bin/python3

import shutil
import re
import threading
from subprocess import Popen, run, DEVNULL, PIPE

USBGUARD_EXEC_NAME = shutil.which('usbguard')
DUNSTIFY_EXEC_NAME = shutil.which('dunstify')
open_notifications = {}


def parse_event_type_and_id(stream):
    line = stream.readline()
    if not line.startswith('[device] '):
        return None
    event_type = re.findall('(?<=\\[device\\] )[a-zA-Z]+', line)
    if len(event_type) == 0:
        return None
    event_id = re.findall('(?<=id=)[0-9]+', line)
    if len(event_id) == 0:
        return None
    return event_type[0], int(event_id[0])


def parse_event_properties(stream, count):
    props = {}
    for _ in range(count):
        line = stream.readline()
        try:
            sep_ind = line.index('=')
            prop_name = line[1:sep_ind]
            props[prop_name] = line[sep_ind + 1:-1]
            if prop_name == 'device_rule':
                break
        except ValueError:
            continue
    return props


def get_name_and_id_from_rule(rule):
    name = re.findall('(?<=name ")[^"]+(?=")', rule)
    if len(name) == 0:
        name = ''
    else:
        name = name[0]
    id = re.findall('(?<=id )[a-z0-9]{4}:[a-z0-9]{4}', rule)
    if len(id) == 0:
        id = ''
    else:
        id = id[0]
    return name, id


def prompt_device_action(dev_id, name, long_id):
    proc = Popen([DUNSTIFY_EXEC_NAME, '-p',
                  '-A', 'block,Block',
                  '-A', 'allow,Allow',
                  '-A', 'reject,Reject',
                  f'{name} ({long_id})',
                  'New Device'],
                 stdout=PIPE, text=True, bufsize=0)
    open_notifications[dev_id] = int(proc.stdout.readline())
    option = proc.communicate()[0][:-1]
    try:
        open_notifications.pop(dev_id)
    except KeyError:
        pass
    match option:
        case 'reject':
            run([USBGUARD_EXEC_NAME, 'reject-device', long_id])

        case 'allow':
            run([USBGUARD_EXEC_NAME, 'allow-device', long_id])

        case _:
            run([USBGUARD_EXEC_NAME, 'block-device', long_id])


def close_notification(dev_id):
    if dev_id in open_notifications:
        notif_id = open_notifications.pop(dev_id)
        run([DUNSTIFY_EXEC_NAME, '-C', str(notif_id)])


with Popen([USBGUARD_EXEC_NAME, 'watch'],
           stdin=DEVNULL, stdout=PIPE, text=True, bufsize=0) as usbguard_proc:
    new_devices = set()
    usbguard_proc.stdout.readline()  # get rid of initial connection message
    while True:
        event_type_result = parse_event_type_and_id(usbguard_proc.stdout)
        if event_type_result is None:
            continue
        event_type, dev_id = event_type_result
        if event_type not in ['PresenceChanged', 'PolicyApplied']:
            continue
        props = parse_event_properties(usbguard_proc.stdout, 3)
        name, long_id = get_name_and_id_from_rule(props['device_rule'])
        match event_type:
            case 'PresenceChanged':
                if props['event'] == 'Insert':
                    new_devices.add(dev_id)
                else:
                    close_notification(dev_id)
                    new_devices.discard(dev_id)
            case 'PolicyApplied':
                if props['target_new'] == 'block':
                    threading.Thread(target=prompt_device_action,
                                     args=(dev_id, name, long_id)).start()
                    new_devices.discard(dev_id)