Source code for pisak.text_tools

"""
Text operations-related tools.
"""
import threading

from gi.repository import GObject, Clutter

from pisak import properties, configurator


class Predictor(Clutter.Actor, properties.PropertyAdapter,
                 configurator.Configurable):
    """
    Base class for objects that follow changes in the given target
    text and supply suggestions based on the text context. Searching
    through a predictor database happens in another thread.

    Properties:

    * :attr:`target`
    """
    __gsignals__ = {
        "content_update": (
            GObject.SIGNAL_RUN_FIRST, None, ()),
        "processing_on": (
            GObject.SIGNAL_RUN_FIRST, None, ())
    }
    __gproperties__ = {
        "target": (
            Clutter.Actor.__gtype__,
            "target to follow",
            "id of text box to follow",
            GObject.PARAM_READWRITE)
    }

    def __init__(self):
        super().__init__()
        self.target = None
        self.content = []

    def get_suggestion(self, accuracy_level):
        """
        Get single suggestion from the list of all generated by the predictor.

        :param accuracy_level: what level of prediction accuracy is required for the
        requested suggestion item.

        :return: single item from the predictor content list.
        """
        if accuracy_level < len(self.content):
            return self.content[accuracy_level]

    def notify_content_update(self):
        """
        Notify that the predictor content has been updated.
        """
        Clutter.threads_add_idle(0, self.emit, "content-update")

    def do_prediction(self, text, position):
        """
        Method that performs the proper action of prediction, based on the given
        text feed. When all the processing is done and content has been updated
        successfully, then it should call the 'notify_content_update' method.
        Method to be overwritten by child.

        :param text: text being the base for prediction.
        :param position: current position in the text.
        """
        raise NotImplementedError

    def _update_content(self, *args):
        self.emit("processing-on")
        text = self.target.get_text()
        position = self.target.get_cursor_position()
        worker = threading.Thread(
            target=self.do_prediction, args=(text, position), daemon=True)
        worker.start()

    def _follow_target(self):
        if self.target is not None:
            text_field = self.target.clutter_text
            text_field.connect("text-changed", self._update_content)

    def _stop_following_target(self):
        try:
            if self.target is not None:
                text_field = self.target.clutter_text
                text_field.disconnect_by_func("text-changed", self._update_content)
        except AttributeError:
            return None

    @property
    def target(self):
        """
        Target object containing text to be watched by the predictor.
        """
        return self._target

    @target.setter
    def target(self, value):
        self._stop_following_target()
        self._target = value
        self._follow_target()