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