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