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"""
Pagination serializers determine the structure of the output that should
be used for paginated responses.
"""
from __future__ import unicode_literals
from django.core.paginator import InvalidPage, Paginator as DjangoPaginator
from django.utils import six
from django.utils.translation import ugettext as _
from rest_framework.compat import OrderedDict
from rest_framework.exceptions import NotFound
from rest_framework.response import Response
from rest_framework.settings import api_settings
from rest_framework.templatetags.rest_framework import replace_query_param
def _strict_positive_int(integer_string, cutoff=None):
"""
Cast a string to a strictly positive integer.
"""
ret = int(integer_string)
if ret <= 0:
raise ValueError()
if cutoff:
ret = min(ret, cutoff)
return ret
class BasePagination(object):
def paginate_queryset(self, queryset, request):
raise NotImplemented('paginate_queryset() must be implemented.')
def get_paginated_response(self, data, page, request):
raise NotImplemented('get_paginated_response() must be implemented.')
class PageNumberPagination(BasePagination):
"""
A simple page number based style that supports page numbers as
query parameters. For example:
http://api.example.org/accounts/?page=4
http://api.example.org/accounts/?page=4&page_size=100
"""
# The default page size.
# Defaults to `None`, meaning pagination is disabled.
paginate_by = api_settings.PAGINATE_BY
# Client can control the page using this query parameter.
page_query_param = 'page'
# Client can control the page size using this query parameter.
# Default is 'None'. Set to eg 'page_size' to enable usage.
paginate_by_param = api_settings.PAGINATE_BY_PARAM
# Set to an integer to limit the maximum page size the client may request.
# Only relevant if 'paginate_by_param' has also been set.
max_paginate_by = api_settings.MAX_PAGINATE_BY
def paginate_queryset(self, queryset, request, view):
"""
Paginate a queryset if required, either returning a page object,
or `None` if pagination is not configured for this view.
"""
for attr in (
'paginate_by', 'page_query_param',
'paginate_by_param', 'max_paginate_by'
):
if hasattr(view, attr):
setattr(self, attr, getattr(view, attr))
page_size = self.get_page_size(request)
if not page_size:
return None
paginator = DjangoPaginator(queryset, page_size)
page_string = request.query_params.get(self.page_query_param, 1)
try:
page_number = paginator.validate_number(page_string)
except InvalidPage:
if page_string == 'last':
page_number = paginator.num_pages
else:
msg = _(
'Choose a valid page number. Page numbers must be a '
'whole number, or must be the string "last".'
)
raise NotFound(msg)
try:
self.page = paginator.page(page_number)
except InvalidPage as exc:
msg = _('Invalid page "{page_number}": {message}.').format(
page_number=page_number, message=six.text_type(exc)
)
raise NotFound(msg)
self.request = request
return self.page
def get_paginated_response(self, objects):
return Response(OrderedDict([
('count', self.page.paginator.count),
('next', self.get_next_link()),
('previous', self.get_previous_link()),
('results', objects)
]))
def get_page_size(self, request):
if self.paginate_by_param:
try:
return _strict_positive_int(
request.query_params[self.paginate_by_param],
cutoff=self.max_paginate_by
)
except (KeyError, ValueError):
pass
return self.paginate_by
def get_next_link(self):
if not self.page.has_next():
return None
url = self.request.build_absolute_uri()
page_number = self.page.next_page_number()
return replace_query_param(url, self.page_query_param, page_number)
def get_previous_link(self):
if not self.page.has_previous():
return None
url = self.request.build_absolute_uri()
page_number = self.page.previous_page_number()
return replace_query_param(url, self.page_query_param, page_number)
class LimitOffsetPagination(BasePagination):
"""
A limit/offset based style. For example:
http://api.example.org/accounts/?limit=100
http://api.example.org/accounts/?offset=400&limit=100
"""
default_limit = api_settings.PAGINATE_BY
limit_query_param = 'limit'
offset_query_param = 'offset'
max_limit = None
def paginate_queryset(self, queryset, request, view):
self.limit = self.get_limit(request)
self.offset = self.get_offset(request)
self.count = queryset.count()
self.request = request
return queryset[self.offset:self.offset + self.limit]
def get_paginated_response(self, objects):
return Response(OrderedDict([
('count', self.count),
('next', self.get_next_link()),
('previous', self.get_previous_link()),
('results', objects)
]))
def get_limit(self, request):
if self.limit_query_param:
try:
return _strict_positive_int(
request.query_params[self.limit_query_param],
cutoff=self.max_limit
)
except (KeyError, ValueError):
pass
return self.default_limit
def get_offset(self, request):
try:
return _strict_positive_int(
request.query_params[self.offset_query_param],
)
except (KeyError, ValueError):
return 0
def get_next_link(self, page):
if self.offset + self.limit >= self.count:
return None
url = self.request.build_absolute_uri()
offset = self.offset + self.limit
return replace_query_param(url, self.offset_query_param, offset)
def get_previous_link(self, page):
if self.offset - self.limit < 0:
return None
url = self.request.build_absolute_uri()
offset = self.offset - self.limit
return replace_query_param(url, self.offset_query_param, offset)
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