mediagoblin/tools/pagination.py

   1 # GNU MediaGoblin -- federated, autonomous media hosting
   2 # Copyright (C) 2011, 2012 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 count
  21 from werkzeug.datastructures import MultiDict
  22
  23 from six.moves import zip
  24
  25 PAGINATION_DEFAULT_PER_PAGE = 30
  26
  27
  28 class Pagination(object):
  29     """
  30     Pagination class for database queries.
  31
  32     Initialization through __init__(self, cursor, page=1, per_page=2),
  33     get actual data slice through __call__().
  34     """
  35
  36     def __init__(self, page, cursor, per_page=PAGINATION_DEFAULT_PER_PAGE,
  37                  jump_to_id=False):
  38         """
  39         Initializes Pagination
  40
  41         Args:
  42          - page: requested page
  43          - per_page: number of objects per page
  44          - cursor: db cursor
  45          - jump_to_id: object id, sets the page to the page containing the
  46            object with id == jump_to_id.
  47         """
  48         self.page = page
  49         self.per_page = per_page
  50         self.cursor = cursor
  51         self.total_count = self.cursor.count()
  52         self.active_id = None
  53
  54         if jump_to_id:
  55             cursor = copy.copy(self.cursor)
  56
  57             for (doc, increment) in list(zip(cursor, count(0))):
  58                 if doc.id == jump_to_id:
  59                     self.page = 1 + int(floor(increment / self.per_page))
  60
  61                     self.active_id = jump_to_id
  62                     break
  63
  64     def __call__(self):
  65         """
  66         Returns slice of objects for the requested page
  67         """
  68         # TODO, return None for out of index so templates can
  69         # distinguish between empty galleries and out-of-bound pages???
  70         return self.cursor.slice(
  71             (self.page - 1) * self.per_page,
  72             self.page * self.per_page)
  73
  74     @property
  75     def pages(self):
  76         return int(ceil(self.total_count / float(self.per_page)))
  77
  78     @property
  79     def has_prev(self):
  80         return self.page > 1
  81
  82     @property
  83     def has_next(self):
  84         return self.page < self.pages
  85
  86     def iter_pages(self, left_edge=2, left_current=2,
  87                    right_current=5, right_edge=2):
  88         last = 0
  89         for num in xrange(1, self.pages + 1):
  90             if num <= left_edge or \
  91                (num > self.page - left_current - 1 and \
  92                 num < self.page + right_current) or \
  93                num > self.pages - right_edge:
  94                 if last + 1 != num:
  95                     yield None
  96                 yield num
  97                 last = num
  98
  99     def get_page_url_explicit(self, base_url, get_params, page_no):
 100         """
 101         Get a page url by adding a page= parameter to the base url
 102         """
 103         if isinstance(get_params, MultiDict):
 104             new_get_params = get_params.to_dict()
 105         else:
 106             new_get_params = dict(get_params) or {}
 107
 108         new_get_params['page'] = page_no
 109         return "%s?%s" % (
 110             base_url, urllib.urlencode(new_get_params))
 111
 112     def get_page_url(self, request, page_no):
 113         """
 114         Get a new page url based of the request, and the new page number.
 115
 116         This is a nice wrapper around get_page_url_explicit()
 117         """
 118         return self.get_page_url_explicit(
 119             request.full_path, request.GET, page_no)