#!/usr/bin/env python3

import math
import functools
import threading
import pyinotify
import os
import time

# TODO Multiple providers for the same section


class Updater:
    @staticmethod
    def init():
        PeriodicUpdater.init()
        InotifyUpdater.init()

    def updateText(self, text):
        print(text)

    def fetcher(self):
        return "{} refreshed".format(self)

    def refreshData(self):
        data = self.fetcher()
        self.updateText(data)


class PeriodicUpdaterThread(threading.Thread):
    def run(self):
        counter = 0
        while True:
            if PeriodicUpdater.intervalsChanged \
                    .wait(timeout=PeriodicUpdater.intervalStep):
                # ↑ sleeps here
                PeriodicUpdater.intervalsChanged.clear()
                counter = 0
                for providerList in PeriodicUpdater.intervals.copy().values():
                    for provider in providerList.copy():
                        provider.refreshData()
            else:
                counter += PeriodicUpdater.intervalStep
                counter = counter % PeriodicUpdater.intervalLoop
                for interval in PeriodicUpdater.intervals.keys():
                    if counter % interval == 0:
                        for provider in PeriodicUpdater.intervals[interval]:
                            provider.refreshData()


class PeriodicUpdater(Updater):
    """
    Needs to call :func:`PeriodicUpdater.changeInterval` in `__init__`
    """

    intervals = dict()
    intervalStep = None
    intervalLoop = None
    updateThread = PeriodicUpdaterThread(daemon=True)
    intervalsChanged = threading.Event()

    @staticmethod
    def gcds(*args):
        return functools.reduce(math.gcd, args)

    @staticmethod
    def lcm(a, b):
        """Return lowest common multiple."""
        return a * b // math.gcd(a, b)

    @staticmethod
    def lcms(*args):
        """Return lowest common multiple."""
        return functools.reduce(PeriodicUpdater.lcm, args)

    @staticmethod
    def updateIntervals():
        intervalsList = list(PeriodicUpdater.intervals.keys())
        PeriodicUpdater.intervalStep = PeriodicUpdater.gcds(*intervalsList)
        PeriodicUpdater.intervalLoop = PeriodicUpdater.lcms(*intervalsList)
        PeriodicUpdater.intervalsChanged.set()

    @staticmethod
    def init():
        PeriodicUpdater.updateThread.start()

    def __init__(self):
        Updater.__init__(self)
        self.interval = None

    def changeInterval(self, interval):
        assert isinstance(interval, int)

        if self.interval is not None:
            PeriodicUpdater.intervals[self.interval].remove(self)

        self.interval = interval

        if interval not in PeriodicUpdater.intervals:
            PeriodicUpdater.intervals[interval] = set()
        PeriodicUpdater.intervals[interval].add(self)

        PeriodicUpdater.updateIntervals()


class InotifyUpdaterEventHandler(pyinotify.ProcessEvent):

    def process_default(self, event):
        # DEBUG
        # from pprint import pprint
        # pprint(event.__dict__)
        # return

        assert event.path in InotifyUpdater.paths

        if 0 in InotifyUpdater.paths[event.path]:
            for provider in InotifyUpdater.paths[event.path][0]:
                provider.refreshData()

        if event.name in InotifyUpdater.paths[event.path]:
            for provider in InotifyUpdater.paths[event.path][event.name]:
                provider.refreshData()


class InotifyUpdater(Updater):
    """
    Needs to call :func:`PeriodicUpdater.changeInterval` in `__init__`
    """

    wm = pyinotify.WatchManager()
    paths = dict()

    @staticmethod
    def init():
        notifier = pyinotify.ThreadedNotifier(InotifyUpdater.wm,
                                              InotifyUpdaterEventHandler())
        notifier.start()

    # TODO Mask for folders
    MASK = pyinotify.IN_CREATE | pyinotify.IN_MODIFY | pyinotify.IN_DELETE

    def addPath(self, path, refresh=True):
        path = os.path.realpath(os.path.expanduser(path))

        # Detect if file or folder
        if os.path.isdir(path):
            self.dirpath = path
            # 0: Directory watcher
            self.filename = 0
        elif os.path.isfile(path):
            self.dirpath = os.path.dirname(path)
            self.filename = os.path.basename(path)
        else:
            raise FileNotFoundError("No such file or directory: '{}'"
                                    .format(path))

        # Register watch action
        if self.dirpath not in InotifyUpdater.paths:
            InotifyUpdater.paths[self.dirpath] = dict()
        if self.filename not in InotifyUpdater.paths[self.dirpath]:
            InotifyUpdater.paths[self.dirpath][self.filename] = set()
        InotifyUpdater.paths[self.dirpath][self.filename].add(self)

        # Add watch
        InotifyUpdater.wm.add_watch(self.dirpath, InotifyUpdater.MASK)

        if refresh:
            self.refreshData()


class ThreadedUpdaterThread(threading.Thread):
    def __init__(self, updater, *args, **kwargs):
        self.updater = updater
        threading.Thread.__init__(self, *args, **kwargs)

    def run(self):
        while True:
            self.updater.loop()


class ThreadedUpdater(Updater):
    """
    Must implement loop(), and call start()
    """

    def __init__(self):
        self.thread = ThreadedUpdaterThread(self, daemon=True)

    def loop(self):
        self.refreshData()
        time.sleep(10)

    def start(self):
        self.thread.start()