mediagoblin/tools/pagination.py

   1 # GNU MediaGoblin -- federated, autonomous media hosting
   2 # Copyright (C) 2011 MediaGoblin contributors.  See AUTHORS.
   3 #
   4 # This program is free software: you can redistribute it and/or modify
   5 # it under the terms of the GNU Affero General Public License as published by
   6 # the Free Software Foundation, either version 3 of the License, or
   7 # (at your option) any later version.
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU Affero General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU Affero General Public License
  15 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 import urllib
  18 import copy
  19 from math import ceil, floor
  20 from itertools import izip, count
  21
  22 PAGINATION_DEFAULT_PER_PAGE = 30
  23
  24 class Pagination(object):
  25     """
  26     Pagination class for mongodb queries.
  27
  28     Initialization through __init__(self, cursor, page=1, per_page=2),
  29     get actual data slice through __call__().
  30     """
  31
  32     def __init__(self, page, cursor, per_page=PAGINATION_DEFAULT_PER_PAGE,
  33                  jump_to_id=False):
  34         """
  35         Initializes Pagination
  36
  37         Args:
  38          - page: requested page
  39          - per_page: number of objects per page
  40          - cursor: db cursor
  41          - jump_to_id: ObjectId, sets the page to the page containing the object
  42            with _id == jump_to_id.
  43         """
  44         self.page = page
  45         self.per_page = per_page
  46         self.cursor = cursor
  47         self.total_count = self.cursor.count()
  48         self.active_id = None
  49
  50         if jump_to_id:
  51             cursor = copy.copy(self.cursor)
  52
  53             for (doc, increment) in izip(cursor, count(0)):
  54                 if doc['_id'] == jump_to_id:
  55                     self.page = 1 + int(floor(increment / self.per_page))
  56
  57                     self.active_id = jump_to_id
  58                     break
  59
  60
  61     def __call__(self):
  62         """
  63         Returns slice of objects for the requested page
  64         """
  65         return self.cursor.skip(
  66             (self.page - 1) * self.per_page).limit(self.per_page)
  67
  68     @property
  69     def pages(self):
  70         return int(ceil(self.total_count / float(self.per_page)))
  71
  72     @property
  73     def has_prev(self):
  74         return self.page > 1
  75
  76     @property
  77     def has_next(self):
  78         return self.page < self.pages
  79
  80     def iter_pages(self, left_edge=2, left_current=2,
  81                    right_current=5, right_edge=2):
  82         last = 0
  83         for num in xrange(1, self.pages + 1):
  84             if num <= left_edge or \
  85                (num > self.page - left_current - 1 and \
  86                 num < self.page + right_current) or \
  87                num > self.pages - right_edge:
  88                 if last + 1 != num:
  89                     yield None
  90                 yield num
  91                 last = num
  92
  93     def get_page_url_explicit(self, base_url, get_params, page_no):
  94         """
  95         Get a page url by adding a page= parameter to the base url
  96         """
  97         new_get_params = copy.copy(get_params or {})
  98         new_get_params['page'] = page_no
  99         return "%s?%s" % (
 100             base_url, urllib.urlencode(new_get_params))
 101
 102     def get_page_url(self, request, page_no):
 103         """
 104         Get a new page url based of the request, and the new page number.
 105
 106         This is a nice wrapper around get_page_url_explicit()
 107         """
 108         return self.get_page_url_explicit(
 109             request.path_info, request.GET, page_no)