from html import escape

from django.contrib.auth import get_user_model
from django.db import transaction
from django.utils.translation import ugettext as _
from django.utils.translation import ugettext_lazy
from reportlab.platypus import Paragraph

from openslides.core.config import config
from openslides.utils.exceptions import OpenSlidesError
from openslides.utils.pdf import stylesheet
from openslides.utils.rest_api import (
    GenericViewSet,
    ListModelMixin,
    Response,
    RetrieveModelMixin,
    UpdateModelMixin,
    ValidationError,
    detail_route,
    list_route,
)
from openslides.utils.views import PDFView

from .models import Item, Speaker
from .serializers import ItemSerializer


# Viewsets for the REST API

class ItemViewSet(ListModelMixin, RetrieveModelMixin, UpdateModelMixin, GenericViewSet):
    """
    API endpoint for agenda items.

    There are the following views: metadata, list, retrieve, create,
    partial_update, update, destroy, manage_speaker, speak and tree.
    """
    queryset = Item.objects.all()
    serializer_class = ItemSerializer

    def check_view_permissions(self):
        """
        Returns True if the user has required permissions.
        """
        if self.action in ('metadata', 'list', 'retrieve', 'manage_speaker', 'tree'):
            result = self.request.user.has_perm('agenda.can_see')
            # For manage_speaker and tree requests the rest of the check is
            # done in the specific method. See below.
        elif self.action in ('partial_update', 'update'):
            result = (self.request.user.has_perm('agenda.can_see') and
                      self.request.user.has_perm('agenda.can_see_hidden_items') and
                      self.request.user.has_perm('agenda.can_manage'))
        elif self.action in ('speak', 'sort_speakers', 'numbering'):
            result = (self.request.user.has_perm('agenda.can_see') and
                      self.request.user.has_perm('agenda.can_manage'))
        else:
            result = False
        return result

    def check_object_permissions(self, request, obj):
        """
        Checks if the requesting user has permission to see also an
        organizational item if it is one.
        """
        if obj.is_hidden() and not request.user.has_perm('agenda.can_see_hidden_items'):
            self.permission_denied(request)

    def get_queryset(self):
        """
        Filters organizational items if the user has no permission to see them.
        """
        queryset = super().get_queryset()
        if self.request.user.has_perm('agenda.can_see_hidden_items'):
            return queryset
        else:
            return Item.objects.get_only_agenda_items(queryset)

    @detail_route(methods=['POST', 'DELETE'])
    def manage_speaker(self, request, pk=None):
        """
        Special view endpoint to add users to the list of speakers or remove
        them. Send POST {'user': <user_id>} to add a new speaker. Omit
        data to add yourself. Send DELETE {'speaker': <speaker_id>} to remove
        someone from the list of speakers. Omit data to remove yourself.

        Checks also whether the requesting user can do this. He needs at
        least the permissions 'agenda.can_see' (see
        self.check_view_permissions()). In case of adding himself the
        permission 'agenda.can_be_speaker' is required. In case of adding
        someone else the permission 'agenda.can_manage' is required. In
        case of removing someone else 'agenda.can_manage' is required. In
        case of removing himself no other permission is required.
        """
        # Retrieve item.
        item = self.get_object()

        if request.method == 'POST':
            # Retrieve user_id
            user_id = request.data.get('user')

            # Check permissions and other conditions. Get user instance.
            if user_id is None:
                # Add oneself
                if not self.request.user.has_perm('agenda.can_be_speaker'):
                    self.permission_denied(request)
                if item.speaker_list_closed:
                    raise ValidationError({'detail': _('The list of speakers is closed.')})
                user = self.request.user
            else:
                # Add someone else.
                if not self.request.user.has_perm('agenda.can_manage'):
                    self.permission_denied(request)
                try:
                    user = get_user_model().objects.get(pk=int(user_id))
                except (ValueError, get_user_model().DoesNotExist):
                    raise ValidationError({'detail': _('User does not exist.')})

            # Try to add the user. This ensurse that a user is not twice in the
            # list of coming speakers.
            try:
                Speaker.objects.add(user, item)
            except OpenSlidesError as e:
                raise ValidationError({'detail': str(e)})
            message = _('User %s was successfully added to the list of speakers.') % user

        else:
            # request.method == 'DELETE'
            # Retrieve speaker_id
            speaker_id = request.data.get('speaker')

            # Check permissions and other conditions. Get speaker instance.
            if speaker_id is None:
                # Remove oneself
                queryset = Speaker.objects.filter(
                    item=item, user=self.request.user).exclude(weight=None)
                try:
                    # We assume that there aren't multiple entries because this
                    # is forbidden by the Manager's add method. We assume that
                    # there is only one speaker instance or none.
                    speaker = queryset.get()
                except Speaker.DoesNotExist:
                    raise ValidationError({'detail': _('You are not on the list of speakers.')})
            else:
                # Remove someone else.
                if not self.request.user.has_perm('agenda.can_manage'):
                    self.permission_denied(request)
                try:
                    speaker = Speaker.objects.get(pk=int(speaker_id))
                except (ValueError, Speaker.DoesNotExist):
                    raise ValidationError({'detail': _('Speaker does not exist.')})

            # Delete the speaker.
            speaker.delete()
            message = _('Speaker %s was successfully removed from the list of speakers.') % speaker

        # Initiate response.
        return Response({'detail': message})

    @detail_route(methods=['PUT', 'DELETE'])
    def speak(self, request, pk=None):
        """
        Special view endpoint to begin and end speech of speakers. Send PUT
        {'speaker': <speaker_id>} to begin speech. Omit data to begin speech of
        the next speaker. Send DELETE to end speech of current speaker.
        """
        # Retrieve item.
        item = self.get_object()

        if request.method == 'PUT':
            # Retrieve speaker_id
            speaker_id = request.data.get('speaker')
            if speaker_id is None:
                speaker = item.get_next_speaker()
                if speaker is None:
                    raise ValidationError({'detail': _('The list of speakers is empty.')})
            else:
                try:
                    speaker = Speaker.objects.get(pk=int(speaker_id))
                except (ValueError, Speaker.DoesNotExist):
                    raise ValidationError({'detail': _('Speaker does not exist.')})
            speaker.begin_speech()
            message = _('User is now speaking.')

        else:
            # request.method == 'DELETE'
            try:
                # We assume that there aren't multiple entries because this
                # is forbidden by the Model's begin_speech method. We assume that
                # there is only one speaker instance or none.
                current_speaker = Speaker.objects.filter(item=item, end_time=None).exclude(begin_time=None).get()
            except Speaker.DoesNotExist:
                raise ValidationError(
                    {'detail': _('There is no one speaking at the moment according to %(item)s.') % {'item': item}})
            current_speaker.end_speech()
            message = _('The speech is finished now.')

        # Initiate response.
        return Response({'detail': message})

    @detail_route(methods=['POST'])
    def sort_speakers(self, request, pk=None):
        """
        Special view endpoint to sort the list of speakers.

        Expects a list of IDs of the speakers.
        """
        # Retrieve item.
        item = self.get_object()

        # Check data
        speaker_ids = request.data.get('speakers')
        if not isinstance(speaker_ids, list):
            raise ValidationError(
                {'detail': _('Invalid data.')})

        # Get all speakers
        speakers = {}
        for speaker in item.speakers.filter(begin_time=None):
            speakers[speaker.pk] = speaker

        # Check and sort speakers
        valid_speakers = []
        for speaker_id in speaker_ids:
            if not isinstance(speaker_id, int) or speakers.get(speaker_id) is None:
                raise ValidationError(
                    {'detail': _('Invalid data.')})
            valid_speakers.append(speakers[speaker_id])
        weight = 0
        with transaction.atomic():
            for speaker in valid_speakers:
                speaker.weight = weight
                speaker.save()
                weight += 1

        # Initiate response.
        return Response({'detail': _('List of speakers successfully sorted.')})

    @list_route(methods=['get', 'put'])
    def tree(self, request):
        """
        Returns or sets the agenda tree.
        """
        if request.method == 'PUT':
            if not (request.user.has_perm('agenda.can_manage') and
                    request.user.has_perm('agenda.can_see_hidden_items')):
                self.permission_denied(request)
            try:
                tree = request.data['tree']
            except KeyError as error:
                response = Response({'detail': 'Agenda tree is missing.'}, status=400)
            else:
                try:
                    Item.objects.set_tree(tree)
                except ValueError as error:
                    response = Response({'detail': str(error)}, status=400)
                else:
                    response = Response({'detail': 'Agenda tree successfully updated.'})
        else:
            # request.method == 'GET'
            response = Response(Item.objects.get_tree())
        return response

    @list_route(methods=['post'])
    def numbering(self, request):
        """
        Auto numbering of the agenda according to the config. Manually added
        item numbers will be overwritten.
        """
        Item.objects.number_all(numeral_system=config['agenda_numeral_system'])
        return Response({'detail': _('The agenda has been numbered.')})


# Views to generate PDFs

class AgendaPDF(PDFView):
    """
    Create a full agenda-PDF.
    """
    required_permission = 'agenda.can_see'
    filename = ugettext_lazy('Agenda')
    document_title = ugettext_lazy('Agenda')

    def append_to_pdf(self, story):
        tree = Item.objects.get_tree(only_agenda_items=True, include_content=True)

        def walk_tree(tree, ancestors=0):
            """
            Generator that yields a two-element-tuple. The first element is an
            agenda-item and the second a number for steps to the root element.
            """
            for element in tree:
                yield element['item'], ancestors
                yield from walk_tree(element['children'], ancestors + 1)

        for item, ancestors in walk_tree(tree):
            if ancestors:
                space = "&nbsp;" * 6 * ancestors
                story.append(Paragraph(
                    "%s%s" % (space, escape(item.title)),
                    stylesheet['Subitem']))
            else:
                story.append(Paragraph(escape(item.title), stylesheet['Item']))