Django template filter for rendering an ellipsized paginator.

paginate.py

from django import template
from django.utils.safestring import mark_safe as safe

register = template.Library()

class PaginationNav(object): 
    def __init__(self, page_number=None, display=None, is_current=False): 
        self.page_number = page_number
        self.is_current = is_current 
        self.display = display or page_number or '' 

@register.filter
def paginate(page, adjacent=2):
    numpages = page.paginator.num_pages
    # Don't paginate if there is only one page
    if numpages <= 1:
        return []

    chunkstart = page.number - adjacent
    chunkend = page.number + adjacent
    ellipsis_pre = True
    ellipsis_post = True

    if chunkstart <= 2:
        ellipsis_pre = False
        chunkstart = 1
        chunkend = max(chunkend, adjacent * 2)

    if chunkend >= (numpages - 1):
        ellipsis_post = False
        chunkend = numpages
        chunkstart = min(chunkstart, numpages - (adjacent * 2) + 1)
    if chunkstart <= 2:
        ellipsis_pre = False

    chunkstart = max(chunkstart, 1)
    chunkend = min(chunkend, numpages)

    def create_page_nav(page_idx):
        return PaginationNav(page_idx, is_current=page_idx == page.number)

    # create page navs in 'chunk' (i.e. middle range)
    pages = [create_page_nav(page_idx)
    for page_idx in range(chunkstart, chunkend + 1)]

    # insert first element and ellipsis if applicable
    if ellipsis_pre:
        pages.insert(0, PaginationNav(display='...'))
        pages.insert(0, create_page_nav(1))

    # append last element and ellipsis if applicable
    if ellipsis_post:
        pages.append(PaginationNav(display='...'))
        pages.append(create_page_nav(page.paginator.num_pages))

    # determine whether we need a 'previous' link and build it
    if page.has_previous():
        pages.insert(0, PaginationNav(page.previous_page_number(), safe('&#xab;')))

    # determine whether we need a 'next' link and build it 
    if page.has_next(): 
        pages.append(PaginationNav(page.next_page_number(), safe('&#xbb;'))) 

    return pages