import cv2
import time
import logging
import dbus


session_bus = dbus.SessionBus()


def tryLock():
    DBUS_DEST = "org.mate.ScreenSaver"
    DBUS_PATH = "/org/mate/ScreenSaver"
    DBUS_IFACE = "org.mate.ScreenSaver"
    proxy = session_bus.get_object(DBUS_DEST, DBUS_PATH)
    screensaver = dbus.Interface(proxy, DBUS_IFACE)

    if screensaver.Hello() == DBUS_DEST:
        if not screensaver.GetActive():
            logging.info("call Lock()")
            screensaver.Lock()
        else:
            logging.debug("Is locked already")
    else:
        logging.error("Mate-Screensaver doesn't answer our call")


def detect(show_window=False):
    face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
    capture = cv2.VideoCapture(0)
    last_seen = time.time()
    try:
        while True:
            ret, frame = capture.read()
            gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

            faces = face_cascade.detectMultiScale(gray, 1.3, 5)
            if len(faces) == 1:
                last_seen = time.time()
            elif time.time() - last_seen > 10:  # sec
                tryLock()

            for (x, y, w, h) in faces:
                cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
                roi_gray = gray[y:y+h, x:x+w]
                roi_color = frame[y:y+h, x:x+w]

            if show_window:
                cv2.imshow("img", frame)
                if cv2.waitKey(500) >= 0:
                    break
            else:
                time.sleep(0.3)
    except KeyboardInterrupt:
        pass

    capture.release()
    if show_window:
        cv2.destroyAllWindows()

if __name__ == "__main__":
    detect(True)