from typing import Generator, Type

from ..core.config import config
from ..core.exceptions import ProjectorException
from ..core.models import Projector
from ..utils.collection import CollectionElement
from ..utils.projector import ProjectorElement
from .models import Item


class ItemListSlide(ProjectorElement):
    """
    Slide definitions for Item model.

    This is only for item list slides.

    Set 'id' to None to get a list slide of all root items. Set 'id' to an
    integer to get a list slide of the children of the metioned item.

    Additionally set 'tree' to True to get also children of children.
    """
    name = 'agenda/item-list'

    def check_data(self):
        pk = self.config_entry.get('id')
        if pk is not None:
            # Children slide.
            if not Item.objects.filter(pk=pk).exists():
                raise ProjectorException('Item does not exist.')

    def get_requirements(self, config_entry):
        yield from Item.objects.all()


class ListOfSpeakersSlide(ProjectorElement):
    """
    Slide definitions for Item model.
    This is only for list of speakers slide. You have to set 'id'.
    """
    name = 'agenda/list-of-speakers'

    def check_data(self):
        if not Item.objects.filter(pk=self.config_entry.get('id')).exists():
            raise ProjectorException('Item does not exist.')

    def get_requirements(self, config_entry):
        pk = config_entry.get('id')
        if pk is not None:
            # List of speakers slide.
            try:
                item = Item.objects.get(pk=pk)
            except Item.DoesNotExist:
                # Item does not exist. Just do nothing.
                pass
            else:
                yield item
                for speaker in item.speakers.filter(end_time=None):
                    # Yield current speaker and next speakers
                    yield speaker.user
                query = (item.speakers.exclude(end_time=None)
                         .order_by('-end_time')[:config['agenda_show_last_speakers']])
                for speaker in query:
                    # Yield last speakers
                    yield speaker.user

    def get_collection_elements_required_for_this(self, collection_element, config_entry):
        output = super().get_collection_elements_required_for_this(collection_element, config_entry)
        # Full update if item changes because then we may have new
        # candidates and therefor need new users.
        if collection_element.collection_string == Item.get_collection_string() and collection_element.id == config_entry.get('id'):
            output.extend(self.get_requirements_as_collection_elements(config_entry))
        return output

    def update_data(self):
        return {'agenda_item_id': self.config_entry.get('id')}


class CurrentListOfSpeakersSlide(ProjectorElement):
    """
    Slide for the current list of speakers.
    """
    name = 'agenda/current-list-of-speakers'

    def get_requirements(self, config_entry):
        # The query mechanism on client needs the referenced projector.
        try:
            reference_projector = Projector.objects.get(
                pk=config['projector_currentListOfSpeakers_reference'])
        except Projector.DoesNotExist:
            # Reference projector was deleted so this projector element is empty.
            # Skip yielding more requirements (items and speakers).
            pass
        else:
            yield reference_projector

            items = self.get_agenda_items(reference_projector)
            for item in items:
                yield item
                for speaker in item.speakers.filter(end_time=None):
                    yield speaker.user
                query = (item.speakers.exclude(end_time=None)
                         .order_by('-end_time')[:config['agenda_show_last_speakers']])
                for speaker in query:
                    # Yield last speakers
                    yield speaker.user

    def get_agenda_items(self, projector):
        for element in projector.elements.values():
            agenda_item_id = element.get('agenda_item_id')
            if agenda_item_id is not None:
                yield Item.objects.get(pk=agenda_item_id)

    def get_collection_elements_required_for_this(self, collection_element, config_entry):
        output = super().get_collection_elements_required_for_this(collection_element, config_entry)
        # Full update if agenda_item or referenced projector changes because
        # then we may have new candidates and therefor need new users.
        try:
            reference_projector = Projector.objects.get(
                pk=config['projector_currentListOfSpeakers_reference'])
        except Projector.DoesNotExist:
            # Reference projector was deleted so this projector element is empty.
            # Skip appending more stuff to output.
            pass
        else:
            is_reference_projector = collection_element == CollectionElement.from_values(
                    reference_projector.get_collection_string(),
                    reference_projector.pk)
            is_config = (
                collection_element.collection_string == 'core/config' and
                collection_element.information.get('changed_config') == 'projector_currentListOfSpeakers_reference')

            if is_reference_projector or is_config:
                output.extend(self.get_requirements_as_collection_elements(config_entry))
            else:
                items = self.get_agenda_items(reference_projector)
                for item in items:
                    if collection_element == CollectionElement.from_values(item.get_collection_string(), item.pk):
                        output.extend(self.get_requirements_as_collection_elements(config_entry))
                        break
        return output


def get_projector_elements() -> Generator[Type[ProjectorElement], None, None]:
    yield ItemListSlide
    yield ListOfSpeakersSlide
    yield CurrentListOfSpeakersSlide