"""Input activity watcher used for the 'turn lighting off when idle' feature."""

import glob
import os
import select
import threading
import time


class IdleWatcher(threading.Thread):
    """Tracks the time of the last keyboard/touchpad/mouse event on any input device."""

    RESCAN = 30  # seconds between scans for new devices (hotplug, resume)

    def __init__(self, on_activity=None):
        super().__init__(daemon=True)
        self.last_input = time.monotonic()
        self.on_activity = on_activity

    def idle_seconds(self):
        return time.monotonic() - self.last_input

    def _open_all(self, fds):
        for path in glob.glob("/dev/input/event*"):
            if path in fds.values():
                continue
            try:
                fds[os.open(path, os.O_RDONLY | os.O_NONBLOCK)] = path
            except OSError:
                pass

    def run(self):
        fds = {}
        next_scan = 0.0
        while True:
            if time.monotonic() >= next_scan:
                self._open_all(fds)
                next_scan = time.monotonic() + self.RESCAN
            if not fds:
                time.sleep(5)
                continue
            ready, _, _ = select.select(list(fds), [], [], 5)
            active = False
            for fd in ready:
                try:
                    if os.read(fd, 4096):
                        active = True
                except BlockingIOError:
                    pass
                except OSError:
                    os.close(fd)
                    fds.pop(fd, None)
            if active:
                self.last_input = time.monotonic()
                if self.on_activity:
                    self.on_activity()