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

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from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler
from collections import deque
from os.path import dirname
class CallbackEventHandler(FileSystemEventHandler):
def __init__(self, *callbacks):
super().__init__()
self.callbacks = callbacks
def on_modified(self, event):
for callback in self.callbacks:
callback()
class HistoryMonitor:
def __init__(self, histfile):
self.histfile = histfile
self._history = deque()
self.observer = Observer()
self.observer.schedule(CallbackEventHandler(self._fetch_history), dirname(self.histfile))
@property
def history(self):
return self._history
def _fetch_history(self):
with open(self.histfile, 'r') as ifile:
self._history = deque(ifile.readlines())
def watch(self):
self.observer.start()
def stop(self):
self.observer.stop()
self.observer.join()