from json import dumps
from time import time

from django.template.loader import render_to_string

from openslides.config.api import config
from openslides.utils.exceptions import OpenSlidesError

from .signals import projector_overlays

slide_callback = {}
"""
A dictonary where the key is the name of a slide, and the value is a
callable object which returns the html code for a slide.
"""

slide_model = {}
"""
A dictonary for SlideMixin models to reference from the slide_callback_name to
the Model
"""
# TODO: Find a bether way to do this. Maybe by reimplementing slides with
#       metaclasses


class SlideError(OpenSlidesError):
    pass


def call_on_projector(calls):
    """
    Sends data to the projector.

    The argument call has to be a dictionary with the javascript function name
    as key and the argument for it as value.
    """
    # TODO: remove this function
    projector_js_cache = config['projector_js_cache']
    projector_js_cache.update(calls)
    config['projector_js_cache'] = projector_js_cache


def get_projector_content(slide_dict=None):
    """
    Returns the HTML-Content block for the projector.

    Slide_dict has to be an dictonary with the key 'callback'.

    If slide_dict is None, use the active slide from the database.
    """
    if slide_dict is None:
        slide_dict = config['projector_active_slide'].copy()
    callback = slide_dict.pop('callback', None)

    try:
        slide_content = slide_callback[callback](**slide_dict)
    except (KeyError, SlideError):
        slide_content = default_slide()
    return slide_content


def default_slide():
    """
    Returns the HTML Code for the default slide.
    """
    return render_to_string('projector/default_slide.html')


def get_overlays(only_active=False):
    """
    Returns all overlay objects.

    If only_active is True, returns only active overlays.

    The returned value is a dictonary with the name of the overlay as key, and
    the overlay object as value.
    """
    overlays = {}
    for receiver, overlay in projector_overlays.send(sender='get_overlays'):
        if not only_active or overlay.is_active():
            overlays[overlay.name] = overlay
    return overlays


def get_projector_overlays_js(as_json=False):
    """
    Returns JS-Code for the active overlays.

    The retuned value is a list of json objects.
    """
    javascript = []
    for overlay in get_overlays().values():
        if overlay.is_active():
            overlay_js = overlay.get_javascript()
            if overlay_js:
                if as_json:
                    overlay_js = dumps(overlay_js)
                javascript.append(overlay_js)
    return javascript


def register_slide(name, callback, model=None):
    """
    Registers a function as slide callback.

    The optional argument 'model' is used to register a SlideModelClass.
    """
    slide_callback[name] = callback
    if model is not None:
        slide_model[name] = model


def register_slide_model(SlideModel, template):
    """
    Shortcut for register_slide for a Model with the SlideMixin.

    The Argument 'SlideModel' has to be a Django-Model-Class, which is a subclass
    of SlideMixin. Template has to be a string to the path of a template.
    """

    def model_slide(**kwargs):
        """
        Return the html code for the model slide.
        """
        slide_pk = kwargs.get('pk', None)

        try:
            slide = SlideModel.objects.get(pk=slide_pk)
        except SlideModel.DoesNotExist:
            raise SlideError
        else:
            context = slide.get_slide_context()

        return render_to_string(template, context)

    register_slide(SlideModel.slide_callback_name, model_slide, SlideModel)


def set_active_slide(callback, **kwargs):
    """
    Set the active Slide.

    callback: The name of the slide callback.
    kwargs: Keyword arguments for the slide callback.
    """
    kwargs.update(callback=callback)
    config['projector_active_slide'] = kwargs


def get_active_slide():
    """
    Returns the dictonary, which defines the active slide.
    """
    return config['projector_active_slide']


def get_active_object():
    """
    Returns an object if the active slide is an instance of SlideMixin.
    In other case, returns None
    """
    active_slide_dict = get_active_slide()
    callback_name = active_slide_dict.get('callback', None)
    object_pk = active_slide_dict.get('pk', None)
    try:
        Model = slide_model[callback_name]
    except KeyError:
        value = None
    else:
        try:
            value = Model.objects.get(pk=object_pk)
        except Model.DoesNotExist:
            value = None
    return value


def start_countdown():
    """
    Starts the countdown
    """
    # if we had stopped the countdown resume were we left of
    if config['countdown_state'] == 'paused':
        start_stamp = config['countdown_start_stamp']
        pause_stamp = config['countdown_pause_stamp']
        now = time()
        config['countdown_start_stamp'] = now - \
            (pause_stamp - start_stamp)
    else:
        config['countdown_start_stamp'] = time()

    config['countdown_state'] = 'active'
    config['countdown_pause_stamp'] = 0


def stop_countdown():
    """
    Stops the countdown
    """
    if config['countdown_state'] == 'active':
        config['countdown_state'] = 'paused'
        config['countdown_pause_stamp'] = time()


def reset_countdown():
    """
    Resets the countdown
    """
    config['countdown_start_stamp'] = time()
    config['countdown_pause_stamp'] = 0
    config['countdown_state'] = 'inactive'