#
# This file is part of gunicorn released under the MIT license.
# See the NOTICE for more information.
# pylint: disable=no-else-continue

import os
import os.path
import re
import sys
import time
import threading

COMPILED_EXT_RE = re.compile(r'py[co]$')


class ReloaderBase(threading.Thread):
    def __init__(self, extra_files=None, interval=1, callback=None):
        super().__init__()
        self.daemon = True
        self._extra_files = set(extra_files or ())
        self._interval = interval
        self._callback = callback

    def add_extra_file(self, filename):
        self._extra_files.add(filename)

    def get_files(self):
        fnames = [
            COMPILED_EXT_RE.sub('py', module.__file__)
            for module in tuple(sys.modules.values())
            if getattr(module, '__file__', None)
        ]

        fnames.extend(self._extra_files)

        return fnames


class Reloader(ReloaderBase):
    def run(self):
        mtimes = {}
        while True:
            for filename in self.get_files():
                try:
                    mtime = os.stat(filename).st_mtime
                except OSError:
                    continue
                old_time = mtimes.get(filename)
                if old_time is None:
                    mtimes[filename] = mtime
                    continue
                elif mtime > old_time:
                    if self._callback:
                        self._callback(filename)
            time.sleep(self._interval)


has_inotify = False
if sys.platform.startswith('linux'):
    try:
        from inotify.adapters import Inotify
        import inotify.constants
        has_inotify = True
    except ImportError:
        pass


if has_inotify:

    class InotifyReloader(ReloaderBase):
        event_mask = (inotify.constants.IN_CREATE | inotify.constants.IN_DELETE
                      | inotify.constants.IN_DELETE_SELF | inotify.constants.IN_MODIFY
                      | inotify.constants.IN_MOVE_SELF | inotify.constants.IN_MOVED_FROM
                      | inotify.constants.IN_MOVED_TO)

        def __init__(self, extra_files=None, callback=None):
            super().__init__(extra_files=extra_files, callback=callback)
            self._dirs = set()
            self._watcher = Inotify()

        def add_extra_file(self, filename):
            super().add_extra_file(filename)

            dirname = os.path.dirname(filename)
            if dirname in self._dirs:
                return

            self._watcher.add_watch(dirname, mask=self.event_mask)
            self._dirs.add(dirname)

        def get_dirs(self):
            dirnames = [os.path.dirname(os.path.abspath(fname)) for fname in self.get_files()]
            return set(dirnames)

        def refresh_dirs(self):
            new_dirs = self.get_dirs().difference(self._dirs)
            self._dirs.update(new_dirs)
            for new_dir in new_dirs:
                if os.path.isdir(new_dir):
                    self._watcher.add_watch(new_dir, mask=self.event_mask)

        def run(self):
            self.refresh_dirs()

            for event in self._watcher.event_gen():
                if event is None:
                    self.refresh_dirs()
                    continue

                filename = event[3]

                self._callback(filename)

else:

    class InotifyReloader:
        def __init__(self, extra_files=None, callback=None):
            raise ImportError('You must have the inotify module installed to '
                              'use the inotify reloader')


preferred_reloader = InotifyReloader if has_inotify else Reloader

reloader_engines = {
    'auto': preferred_reloader,
    'poll': Reloader,
    'inotify': InotifyReloader,
}