def edit(request, user_id):
    user = get_object_or_404(User, pk=user_id)
    can_delete = user_can_delete_user(request.user, user)
    editing_self = request.user == user

    for fn in hooks.get_hooks('before_edit_user'):
        result = fn(request, user)
        if hasattr(result, 'status_code'):
            return result
    if request.method == 'POST':
        form = get_user_edit_form()(request.POST, request.FILES, instance=user, editing_self=editing_self)
        if form.is_valid():
            user = form.save()
            messages.success(request, _("User '{0}' updated.").format(user), buttons=[
                messages.button(reverse('wagtailusers_users:edit', args=(user.pk,)), _('Edit'))
            ])
            for fn in hooks.get_hooks('after_edit_user'):
                result = fn(request, user)
                if hasattr(result, 'status_code'):
                    return result
            return redirect('wagtailusers_users:index')
        else:
            messages.error(request, _("The user could not be saved due to errors."))
    else:
        form = get_user_edit_form()(instance=user, editing_self=editing_self)

    return render(request, 'wagtailusers/users/edit.html', {
        'user': user,
        'form': form,
        'can_delete': can_delete,
    })

def edit(request, user_id):
    user = get_object_or_404(User, pk=user_id)
    can_delete = user_can_delete_user(request.user, user)
    editing_self = request.user == user

    for fn in hooks.get_hooks('before_edit_user'):
        result = fn(request, user)
        if hasattr(result, 'status_code'):
            return result
    if request.method == 'POST':
        form = get_user_edit_form()(request.POST, request.FILES, instance=user, editing_self=editing_self)
        if form.is_valid():
            user = form.save()
            messages.success(request, _("Your details have been updated. You've been logged out for security reasons, "
                                        "please login to continue."))
            for fn in hooks.get_hooks('after_edit_user'):
                result = fn(request, user)
                if hasattr(result, 'status_code'):
                    return result
            return redirect('wagtailusers_users:index')
        else:
            messages.error(request, _("The user could not be saved due to errors."))
    else:
        form = get_user_edit_form()(instance=user, editing_self=editing_self)

    return render(request, 'wagtailusers/users/edit.html', {
        'user': user,
        'form': form,
        'can_delete': can_delete,
    })

def create(request):
    for fn in hooks.get_hooks('before_create_user'):
        result = fn(request)
        if hasattr(result, 'status_code'):
            return result
    if request.method == 'POST':
        form = get_user_creation_form()(request.POST, request.FILES)
        if form.is_valid():
            user = form.save()
            messages.success(request, _("User '{0}' created.").format(user), buttons=[
                messages.button(reverse('wagtailusers_users:edit', args=(user.pk,)), _('Edit'))
            ])
            for fn in hooks.get_hooks('after_create_user'):
                result = fn(request, user)
                if hasattr(result, 'status_code'):
                    return result
            return redirect('wagtailusers_users:index')
        else:
            messages.error(request, _("The user could not be created due to errors."))
    else:
        form = get_user_creation_form()()

    return render(request, 'wagtailusers/users/create.html', {
        'form': form,
    })

def delete(request, page_id):
    page = get_object_or_404(Page, id=page_id).specific
    if not page.permissions_for_user(request.user).can_delete():
        raise PermissionDenied

    with transaction.atomic():
        for fn in hooks.get_hooks('before_delete_page'):
            result = fn(request, page)
            if hasattr(result, 'status_code'):
                return result

        next_url = get_valid_next_url_from_request(request)

        if request.method == 'POST':
            parent_id = page.get_parent().id
            page.delete()

            messages.success(request, _("Page '{0}' deleted.").format(page.get_admin_display_title()))

            for fn in hooks.get_hooks('after_delete_page'):
                result = fn(request, page)
                if hasattr(result, 'status_code'):
                    return result

            if next_url:
                return redirect(next_url)
            return redirect('wagtailadmin_explore', parent_id)

    return render(request, 'wagtailadmin/pages/confirm_delete.html', {
        'page': page,
        'descendant_count': page.get_descendant_count(),
        'next': next_url,
    })

def home(request):

    panels = [
        SiteSummaryPanel(request),
        UpgradeNotificationPanel(request),
        PagesForModerationPanel(request),
        RecentEditsPanel(request),
    ]

    for fn in hooks.get_hooks('construct_homepage_panels'):
        fn(request, panels)

    root_page = get_explorable_root_page(request.user)
    if root_page:
        root_site = root_page.get_site()
    else:
        root_site = None

    real_site_name = None
    if root_site:
        real_site_name = root_site.site_name if root_site.site_name else root_site.hostname

    return render(request, "wagtailadmin/home.html", {
        'root_page': root_page,
        'root_site': root_site,
        'site_name': real_site_name if real_site_name else settings.WAGTAIL_SITE_NAME,
        'panels': sorted(panels, key=lambda p: p.order),
        'user': request.user
    })

    def test_after_hook(self):
        def after_hook():
            pass

        with self.register_hook('test_hook_name', after_hook, order=1):
            hook_fns = hooks.get_hooks('test_hook_name')
            self.assertEqual(hook_fns, [test_hook, after_hook])

    def test_before_hook(self):
        def before_hook():
            pass

        with self.register_hook('test_hook_name', before_hook, order=-1):
            hook_fns = hooks.get_hooks('test_hook_name')
            self.assertEqual(hook_fns, [before_hook, test_hook])

def chooser(request):
    Image = get_image_model()

    if permission_policy.user_has_permission(request.user, 'add'):
        ImageForm = get_image_form(Image)
        uploadform = ImageForm(user=request.user)
    else:
        uploadform = None

    images = Image.objects.order_by('-created_at')

    # allow hooks to modify the queryset
    for hook in hooks.get_hooks('construct_image_chooser_queryset'):
        images = hook(images, request)

    if (
        'q' in request.GET or 'p' in request.GET or 'tag' in request.GET or
        'collection_id' in request.GET
    ):
        # this request is triggered from search, pagination or 'popular tags';
        # we will just render the results.html fragment
        collection_id = request.GET.get('collection_id')
        if collection_id:
            images = images.filter(collection=collection_id)

        searchform = SearchForm(request.GET)
        if searchform.is_valid():
            q = searchform.cleaned_data['q']

            images = images.search(q)
            is_searching = True
        else:
            is_searching = False
            q = None

            tag_name = request.GET.get('tag')
            if tag_name:
                images = images.filter(tags__name=tag_name)

        # Pagination
        paginator, images = paginate(request, images, per_page=12)

        return render(request, "wagtailimages/chooser/results.html", {
            'images': images,
            'is_searching': is_searching,
            'query_string': q,
            'will_select_format': request.GET.get('select_format')
        })
    else:
        paginator, images = paginate(request, images, per_page=12)

        context = get_chooser_context(request)
        context.update({
            'images': images,
            'uploadform': uploadform,
        })
        return render_modal_workflow(
            request, 'wagtailimages/chooser/chooser.html', None, context,
            json_data=get_chooser_js_data()
        )

def chooser_upload(request):
    Image = get_image_model()
    ImageForm = get_image_form(Image)

    if request.method == 'POST':
        image = Image(uploaded_by_user=request.user)
        form = ImageForm(
            request.POST, request.FILES, instance=image, user=request.user, prefix='image-chooser-upload'
        )

        if form.is_valid():
            # Set image file size
            image.file_size = image.file.size

            # Set image file hash
            image.file.seek(0)
            image._set_file_hash(image.file.read())
            image.file.seek(0)

            form.save()

            # Reindex the image to make sure all tags are indexed
            search_index.insert_or_update_object(image)

            if request.GET.get('select_format'):
                form = ImageInsertionForm(
                    initial={'alt_text': image.default_alt_text}, prefix='image-chooser-insertion'
                )
                return render_modal_workflow(
                    request, 'wagtailimages/chooser/select_format.html', None,
                    {'image': image, 'form': form}, json_data={'step': 'select_format'}
                )
            else:
                # not specifying a format; return the image details now
                return render_modal_workflow(
                    request, None, None,
                    None, json_data={'step': 'image_chosen', 'result': get_image_result_data(image)}
                )
    else:
        form = ImageForm(user=request.user, prefix='image-chooser-upload')

    images = Image.objects.order_by('-created_at')

    # allow hooks to modify the queryset
    for hook in hooks.get_hooks('construct_image_chooser_queryset'):
        images = hook(images, request)

    paginator = Paginator(images, per_page=12)
    images = paginator.get_page(request.GET.get('p'))

    context = get_chooser_context(request)
    context.update({
        'images': images,
        'uploadform': form,
    })
    return render_modal_workflow(
        request, 'wagtailimages/chooser/chooser.html', None, context,
        json_data=get_chooser_js_data()
    )

def get_permission_panel_classes():
    global _permission_panel_classes
    if _permission_panel_classes is None:
        _permission_panel_classes = [GroupPagePermissionFormSet]
        for fn in hooks.get_hooks('register_group_permission_panel'):
            _permission_panel_classes.append(fn())

    return _permission_panel_classes

 def test_registered_permission(self):
     permission = Permission.objects.get_by_natural_key(
         app_label='tests', model='testsetting', codename='change_testsetting')
     for fn in hooks.get_hooks('register_permissions'):
         if permission in fn():
             break
     else:
         self.fail('Change permission for tests.TestSetting not registered')

def chooser(request):
    Document = get_document_model()

    if permission_policy.user_has_permission(request.user, 'add'):
        DocumentForm = get_document_form(Document)
        uploadform = DocumentForm(user=request.user)
    else:
        uploadform = None

    documents = Document.objects.all()

    # allow hooks to modify the queryset
    for hook in hooks.get_hooks('construct_document_chooser_queryset'):
        documents = hook(documents, request)

    q = None
    if 'q' in request.GET or 'p' in request.GET or 'collection_id' in request.GET:

        collection_id = request.GET.get('collection_id')
        if collection_id:
            documents = documents.filter(collection=collection_id)

        searchform = SearchForm(request.GET)
        if searchform.is_valid():
            q = searchform.cleaned_data['q']

            documents = documents.search(q)
            is_searching = True
        else:
            documents = documents.order_by('-created_at')
            is_searching = False

        # Pagination
        paginator, documents = paginate(request, documents, per_page=10)

        return render(request, "wagtaildocs/chooser/results.html", {
            'documents': documents,
            'query_string': q,
            'is_searching': is_searching,
        })
    else:
        searchform = SearchForm()

        collections = Collection.objects.all()
        if len(collections) < 2:
            collections = None

        documents = documents.order_by('-created_at')
        paginator, documents = paginate(request, documents, per_page=10)

        return render_modal_workflow(request, 'wagtaildocs/chooser/chooser.html', 'wagtaildocs/chooser/chooser.js', {
            'documents': documents,
            'uploadform': uploadform,
            'searchform': searchform,
            'collections': collections,
            'is_searching': False,
            'uploadid': uuid.uuid4(),
        })

    def _search_for_operations(cls):
        if cls._registered_operations is not None:
            return

        operations = []
        for fn in hooks.get_hooks('register_image_operations'):
            operations.extend(fn())

        cls._registered_operations = dict(operations)

def hook_output(hook_name):
    """
    Example: {% hook_output 'insert_editor_css' %}
    Whenever we have a hook whose functions take no parameters and return a string, this tag can be used
    to output the concatenation of all of those return values onto the page.
    Note that the output is not escaped - it is the hook function's responsibility to escape unsafe content.
    """
    snippets = [fn() for fn in hooks.get_hooks(hook_name)]
    return mark_safe(''.join(snippets))

def serve(request, document_id, document_filename):
    Document = get_document_model()
    doc = get_object_or_404(Document, id=document_id)

    # We want to ensure that the document filename provided in the URL matches the one associated with the considered
    # document_id. If not we can't be sure that the document the user wants to access is the one corresponding to the
    # <document_id, document_filename> pair.
    if doc.filename != document_filename:
        raise Http404('This document does not match the given filename.')

    for fn in hooks.get_hooks('before_serve_document'):
        result = fn(doc, request)
        if isinstance(result, HttpResponse):
            return result

    # Send document_served signal
    document_served.send(sender=Document, instance=doc, request=request)

    try:
        local_path = doc.file.path
    except NotImplementedError:
        local_path = None

    if local_path:

        # Use wagtail.utils.sendfile to serve the file;
        # this provides support for mimetypes, if-modified-since and django-sendfile backends

        if hasattr(settings, 'SENDFILE_BACKEND'):
            return sendfile(request, local_path, attachment=True, attachment_filename=doc.filename)
        else:
            # Fallback to streaming backend if user hasn't specified SENDFILE_BACKEND
            return sendfile(
                request,
                local_path,
                attachment=True,
                attachment_filename=doc.filename,
                backend=sendfile_streaming_backend.sendfile
            )

    else:

        # We are using a storage backend which does not expose filesystem paths
        # (e.g. storages.backends.s3boto.S3BotoStorage).
        # Fall back on pre-sendfile behaviour of reading the file content and serving it
        # as a StreamingHttpResponse

        wrapper = FileWrapper(doc.file)
        response = StreamingHttpResponse(wrapper, content_type='application/octet-stream')

        response['Content-Disposition'] = 'attachment; filename=%s' % doc.filename

        # FIXME: storage backends are not guaranteed to implement 'size'
        response['Content-Length'] = doc.file.size

        return response

    def filter_queryset(self, request, queryset, view):
        if request.GET.get('for_explorer'):
            if not hasattr(queryset, '_filtered_by_child_of'):
                raise BadRequestError("filtering by for_explorer without child_of is not supported")

            parent_page = queryset._filtered_by_child_of
            for hook in hooks.get_hooks('construct_explorer_page_queryset'):
                queryset = hook(parent_page, queryset, request)

        return queryset

def account(request):
    items = []

    for fn in hooks.get_hooks('register_account_menu_item'):
        item = fn(request)
        if item:
            items.append(item)

    return render(request, 'wagtailadmin/account/account.html', {
        'items': items,
    })

def get_forms_for_user(user):
    """
    Return a queryset of form pages that this user is allowed to access the submissions for
    """
    editable_forms = UserPagePermissionsProxy(user).editable_pages()
    editable_forms = editable_forms.filter(content_type__in=get_form_types())

    # Apply hooks
    for fn in hooks.get_hooks('filter_form_submissions_for_user'):
        editable_forms = fn(user, editable_forms)

    return editable_forms

    def get_collection_contents(self):
        collection_contents = [
            hook(self.object)
            for hook in hooks.get_hooks('describe_collection_contents')
        ]

        # filter out any hook responses that report that the collection is empty
        # (by returning None, or a dict with 'count': 0)
        def is_nonempty(item_type):
            return item_type and item_type['count'] > 0

        return list(filter(is_nonempty, collection_contents))

    def render_html(self, request):
        menu_items = self.menu_items_for_request(request)

        # provide a hook for modifying the menu, if construct_hook_name has been set
        if self.construct_hook_name:
            for fn in hooks.get_hooks(self.construct_hook_name):
                fn(request, menu_items)

        rendered_menu_items = []
        for item in sorted(menu_items, key=lambda i: i.order):
            rendered_menu_items.append(item.render_html(request))

        return mark_safe(''.join(rendered_menu_items))