OpenSlides/openslides/utils/views.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
    openslides.utils.views
    ~~~~~~~~~~~~~~~~~~~~~~

    Views for OpenSlides.

    :copyright: 2011–2013 by OpenSlides team, see AUTHORS.
    :license: GNU GPL, see LICENSE for more details.
"""

import json
from cStringIO import StringIO

from django.conf import settings
from django.contrib import messages
from django.contrib.auth.decorators import login_required
from django.core.context_processors import csrf
from django.core.exceptions import ImproperlyConfigured, PermissionDenied
from django.core.urlresolvers import reverse
from django.dispatch import receiver
from django.http import (HttpResponse, HttpResponseRedirect,
                         HttpResponseServerError)
from django.template import RequestContext
from django.template.loader import render_to_string
from django.utils.decorators import method_decorator
from django.utils.importlib import import_module
from django.utils.translation import ugettext as _
from django.utils.translation import ugettext_lazy
from django.views import generic as django_views
from django.views.generic.detail import SingleObjectMixin
from reportlab.lib.units import cm
from reportlab.platypus import SimpleDocTemplate, Spacer

from .pdf import firstPage, laterPages
from .signals import template_manipulation
from .utils import html_strong

NO_PERMISSION_REQUIRED = 'No permission required'

View = django_views.View


class LoginMixin(object):
    """
    Mixin for Views, that only can be viseted from users how are logedin.
    """

    @method_decorator(login_required)
    def dispatch(self, request, *args, **kwargs):
        """
        Check if the user is loged in.
        """
        return super(LoginMixin, self).dispatch(request, *args, **kwargs)


class PermissionMixin(object):
    """
    Mixin for views, that only can be visited from users with special rights.

    Set the attribute 'permission_required' to the required permission string.
    """
    permission_required = NO_PERMISSION_REQUIRED

    def has_permission(self, request, *args, **kwargs):
        """
        Checks if the user has the required permission.
        """
        if self.permission_required == NO_PERMISSION_REQUIRED:
            return True
        else:
            return request.user.has_perm(self.permission_required)

    def dispatch(self, request, *args, **kwargs):
        """
        Check if the user has the permission.

        If the user is not logged in, redirect the user to the login page.
        """
        if not self.has_permission(request, *args, **kwargs):
            if not request.user.is_authenticated():
                path = request.get_full_path()
                return HttpResponseRedirect(
                    "%s?next=%s" % (settings.LOGIN_URL, path))
            else:
                raise PermissionDenied
        return super(PermissionMixin, self).dispatch(request, *args, **kwargs)


class AjaxMixin(object):
    """
    Mixin to response to an ajax request with an json object.
    """

    def get_ajax_context(self, **kwargs):
        """
        Returns a dictonary with the context for the ajax response.
        """
        return kwargs

    def ajax_get(self, request, *args, **kwargs):
        """
        Returns the HttpResponse.
        """
        return HttpResponse(json.dumps(self.get_ajax_context()))


class ExtraContextMixin(object):
    """
    Mixin to send the signal 'template_manipulation' to add extra content to the
    context of the view.

    For example this is used to add the main menu of openslides.
    """

    def get_context_data(self, **kwargs):
        """
        Sends the signal.
        """
        context = super(ExtraContextMixin, self).get_context_data(**kwargs)
        template_manipulation.send(
            sender=self.__class__, request=self.request, context=context)
        return context


class UrlMixin(object):
    url_name_args = None

    def get_url(self, url_name=None, url=None, args=None, use_absolute_url_link=None):
        """
        Returns an url.

        Tries
        1. to use the reverse for the attribute 'url_name',
        2. to use the attribute 'url' or
        3. to use self.object.get_absolute_url().

        Uses the attribute 'use_absolute_url_link' as argument for
        get_absolute_url in the third step. If the attribute is 'None' then
        the default value of get_absolute_url is used.

        Raises ImproperlyConfigured if no url can be found.
        """
        if url_name:
            value = reverse(url_name, args=args or [])
        elif url:
            value = url
        else:
            try:
                if use_absolute_url_link is None:
                    value = self.object.get_absolute_url()
                else:
                    value = self.object.get_absolute_url(use_absolute_url_link)
            except AttributeError:
                raise ImproperlyConfigured(
                    'No url to redirect to. See openslides.utils.views.UrlMixin for more details.')
        return value

    def get_url_name_args(self):
        """
        Returns the arguments for the url name.

        Default is an empty list or [self.object.pk] if this exist.
        """
        if self.url_name_args is not None:
            value = self.url_name_args
        else:
            try:
                pk = self.object.pk
            except AttributeError:
                value = []
            else:
                if pk:
                    value = [pk]
                else:
                    value = []
        return value


class FormMixin(UrlMixin):
    """
    Mixin for views with forms.
    """

    use_apply = True
    success_url_name = None
    success_url = None
    success_message = None
    apply_url_name = None
    apply_url = None
    error_message = ugettext_lazy('Please check the form for errors.')

    def get_apply_url(self):
        """
        Returns the url when the user clicks on 'apply'.
        """
        return self.get_url(self.apply_url_name, self.apply_url,
                            args=self.get_url_name_args(),
                            use_absolute_url_link='update')

    def get_success_url(self):
        """
        Returns the url when the user submits a form.

        Redirects to get_apply_url if self.use_apply is True
        """
        if self.use_apply and 'apply' in self.request.POST:
            value = self.get_apply_url()
        else:
            value = self.get_url(self.success_url_name, self.success_url,
                                 args=self.get_url_name_args())
        return value

    def form_valid(self, form):
        value = super(FormMixin, self).form_valid(form)
        messages.success(self.request, self.get_success_message())
        return value

    def form_invalid(self, form):
        value = super(FormMixin, self).form_invalid(form)
        messages.error(self.request, self.get_error_message())
        return value

    def get_success_message(self):
        return self.success_message

    def get_error_message(self):
        return self.error_message


class ModelFormMixin(FormMixin):
    """
    Mixin for FormViews.
    """

    def form_valid(self, form):
        """
        Called if the form is valid.

        1. saves the form into the model,
        2. calls 'self.manipulate_object,
        3. saves the object in the database,
        4. calls self.post_save.
        """
        self.object = form.save(commit=False)
        self.manipulate_object(form)
        self.object.save()
        self.post_save(form)
        messages.success(self.request, self.get_success_message())
        return HttpResponseRedirect(self.get_success_url())

    def manipulate_object(self, form):
        """
        Called before the object is saved into the database.
        """
        pass

    def post_save(self, form):
        """
        Called after the object is saved into the database.
        """
        form.save_m2m()


class TemplateView(PermissionMixin, ExtraContextMixin, django_views.TemplateView):
    """
    View to return with an template.
    """
    pass


class ListView(PermissionMixin, ExtraContextMixin, django_views.ListView):
    """
    View to show a list of model objects.
    """
    pass


class AjaxView(PermissionMixin, AjaxMixin, View):
    """
    View for ajax requests.
    """
    def get(self, request, *args, **kwargs):
        return self.ajax_get(request, *args, **kwargs)


class RedirectView(PermissionMixin, AjaxMixin, UrlMixin, django_views.RedirectView):
    """
    View to redirect to another url.

    The initial value of url_name_args is None, but the default given by
    the used get_url_name_args method is [self.object.pk] if it exist, else
    an empty list. Set url_name_args to an empty list, if you use an url
    name which does not need any arguments.
    """
    permanent = False
    allow_ajax = False
    url_name = None

    def pre_redirect(self, request, *args, **kwargs):
        """
        Called before the redirect.
        """
        # TODO: Also call this method on post-request.
        #       Add pre_get_redirect for get requests.
        pass

    def pre_post_redirect(self, request, *args, **kwargs):
        """
        Called before the redirect, if it is a post request.
        """
        pass

    def get(self, request, *args, **kwargs):
        if request.method == 'GET':
            self.pre_redirect(request, *args, **kwargs)
        elif request.method == 'POST':
            self.pre_post_redirect(request, *args, **kwargs)

        if request.is_ajax() and self.allow_ajax:
            return self.ajax_get(request, *args, **kwargs)
        return super(RedirectView, self).get(request, *args, **kwargs)

    def get_redirect_url(self, **kwargs):
        """
        Returns the url to which the redirect should go.
        """
        return self.get_url(self.url_name, self.url,
                            args=self.get_url_name_args())


class QuestionView(RedirectView):
    """
    Mixin for questions to the requesting user.

    The BaseView has to be a RedirectView.
    """

    question_message = ugettext_lazy('Are you sure?')
    final_message = ugettext_lazy('Thank you for your answer.')
    answer_options = [('yes', ugettext_lazy("Yes")), ('no', ugettext_lazy("No"))]
    question_url_name = None
    question_url = None

    def get_redirect_url(self, **kwargs):
        """
        Returns the url to which the view should redirect.
        """
        if self.request.method == 'GET':
            url = self.get_url(self.question_url_name, self.question_url,
                               args=self.get_url_name_args())
        else:
            url = super(QuestionView, self).get_redirect_url()
        return url

    def pre_redirect(self, request, *args, **kwargs):
        """
        Prints the question in a GET request.
        """
        self.confirm_form()

    def get_question_message(self):
        """
        Returns the question.
        """
        return self.question_message

    def get_answer_options(self):
        """
        Returns the possible answers.

        This is a list of tubles. The first element of the tuble is the key,
        the second element is shown to the user.
        """
        return self.answer_options

    def confirm_form(self):
        """
        Returns the form to show in the message.
        """
        option_fields = "\n".join([
            '<button type="submit" class="btn btn-mini" name="%s">%s</button>'
            % (option[0], unicode(option[1]))
            for option in self.get_answer_options()])
        messages.warning(
            self.request,
            """
            %(message)s
            <form action="%(url)s" method="post">
                <input type="hidden" value="%(csrf)s" name="csrfmiddlewaretoken">
                %(option_fields)s
            </form>
            """ % {'message': self.get_question_message(),
                   'url': self.request.path,
                   'csrf': csrf(self.request)['csrf_token'],
                   'option_fields': option_fields})

    def pre_post_redirect(self, request, *args, **kwargs):
        """
        Calls the method for the answer the user clicked.

        The method name is on_clicked_ANSWER where ANSWER is the key from the
        clicked answer. See get_answer_options. If this method is not defined,
        raises a NotImplementedError.

        If the method returns True, then the success message is printed to the
        user.
        """
        method_name = 'on_clicked_%s' % self.get_answer()
        method = getattr(self, method_name, None)
        if method is None:
            pass
        else:
            method()
            self.create_final_message()

    def get_answer(self):
        """
        Returns the key of the clicked answer.

        Raises ImproperlyConfigured, if the answer is not one of
        get_answer_options.
        """
        for option_key, option_name in self.get_answer_options():
            if option_key in self.request.POST:
                return option_key
        raise ImproperlyConfigured('%s is not a valid answer' % self.request.POST)

    def get_final_message(self):
        """
        Returns the message to show after the action.

        Uses the attribute 'final_messsage' as default
        """
        return self.final_message

    def create_final_message(self):
        """
        Creates a message.
        """
        messages.success(self.request, self.get_final_message())


class FormView(PermissionMixin, ExtraContextMixin, FormMixin,
               django_views.FormView):
    """
    View for forms.
    """
    pass


class UpdateView(PermissionMixin, ExtraContextMixin,
                 ModelFormMixin, django_views.UpdateView):
    """
    View to update an model object.
    """

    def get_success_message(self):
        if self.success_message is None:
            message = _('%s was successfully modified.') % html_strong(self.object)
        else:
            message = self.success_message
        return message


class CreateView(PermissionMixin, ExtraContextMixin,
                 ModelFormMixin, django_views.CreateView):
    """
    View to create a model object.
    """

    def get_success_message(self):
        if self.success_message is None:
            message = _('%s was successfully created.') % html_strong(self.object)
        else:
            message = self.success_message
        return message


class DeleteView(SingleObjectMixin, QuestionView):
    """
    View to delete an model object.
    """

    success_url = None
    success_url_name = None

    def get(self, request, *args, **kwargs):
        self.object = self.get_object()
        return super(DeleteView, self).get(request, *args, **kwargs)

    def get_redirect_url(self, **kwargs):
        """
        Returns the url on which the delete dialog is shown and the url after
        the deleten.

        On GET-requests and on aborted POST-requests, redirect to the detail
        view as default. The attributes question_url_name or question_url can
        define other urls.
        """
        if self.request.method == 'GET' or self.get_answer() == 'no':
            url = self.get_url(self.question_url_name, self.question_url,
                               args=self.get_url_name_args())
        else:
            url = self.get_url(self.success_url_name, self.success_url,
                               args=self.get_url_name_args())
        return url

    def get_question_message(self):
        """
        Returns the question for the delete dialog.
        """
        return _('Do you really want to delete %s?') % html_strong(self.object)

    def on_clicked_yes(self):
        """
        Deletes the object.
        """
        self.object.delete()

    def get_final_message(self):
        """
        Prints the success message to the user.
        """
        return _('%s was successfully deleted.') % html_strong(self.object)


class DetailView(PermissionMixin, ExtraContextMixin, django_views.DetailView):
    """
    View to show an model object.
    """
    pass


class PDFView(PermissionMixin, View):
    """
    View to generate an PDF.
    """

    filename = _('undefined-filename')
    top_space = 3
    document_title = None

    def get_top_space(self):
        return self.top_space

    def get_document_title(self):
        if self.document_title:
            return unicode(self.document_title)
        else:
            return ''

    def get_filename(self):
        return self.filename

    def get_template(self, buffer):
        return SimpleDocTemplate(buffer)

    def build_document(self, pdf_document, story):
        pdf_document.build(
            story, onFirstPage=firstPage, onLaterPages=laterPages)

    def render_to_response(self, filename):
        response = HttpResponse(mimetype='application/pdf')
        filename = u'filename=%s.pdf;' % self.get_filename()
        response['Content-Disposition'] = filename.encode('utf-8')

        buffer = StringIO()
        pdf_document = self.get_template(buffer)
        pdf_document.title = self.get_document_title()
        story = [Spacer(1, self.get_top_space() * cm)]

        self.append_to_pdf(story)

        self.build_document(pdf_document, story)

        pdf = buffer.getvalue()
        buffer.close()
        response.write(pdf)
        return response

    def get(self, request, *args, **kwargs):
        return self.render_to_response(self.get_filename())


def server_error(request, template_name='500.html'):
    """
    500 error handler.

    Templates: `500.html`
    """
    return HttpResponseServerError(render_to_string(
        template_name, context_instance=RequestContext(request)))


@receiver(template_manipulation, dispatch_uid="send_register_tab")
def send_register_tab(sender, request, context, **kwargs):
    """
    Receiver to the template_manipulation signal. Collects from the file
    views.py in all apps the tabs setup by the function register_tab.
    Inserts the tab objects and also the extra_stylefiles to the context.
    """
    tabs = []
    if 'extra_stylefiles' in context:
        extra_stylefiles = context['extra_stylefiles']
    else:
        extra_stylefiles = []
    context.setdefault('extra_javascript', [])

    # TODO: Do not go over the filesystem by any request
    for app in settings.INSTALLED_APPS:
        try:
            mod = import_module(app + '.views')
            tab = mod.register_tab(request)
            tabs.append(tab)
            if tab.stylefile:
                extra_stylefiles.append(tab.stylefile)
        except (ImportError, AttributeError):
            continue
    context.update({
        'tabs': tabs,
        'extra_stylefiles': extra_stylefiles})