pagination.py

from math import ceil
from mongoengine.queryset import QuerySet

__all__ = ('paginate',)


def paginate(page=1,
             total=0,
             adjacents=2,
             per_page=1,
             iterable=None):
    """
    >> paginate(page=7, total=200, adjacents=2, per_page=4)
    {'items': None,
     'page': 7,
     'pages': [5, 6, 7, 8, 9],
     'total': 200,
     'total_pages': 50}

    >> paginate(page=50, total=200, adjacents=2, per_page=4)
    {'items': None,
     'page': 50,
     'pages': [46, 47, 48, 49, 50],
     'total': 200,
     'total_pages': 50}

    >> paginate(page=50, total=200, adjacents=3, per_page=4)
    {'items': None,
     'page': 50,
     'pages': [44, 45, 46, 47, 48, 49, 50],
     'total': 200,
     'total_pages': 50}
    """
    try:
        page = int(page) or 1
    except (ValueError, TypeError):
        page = 1

    items = None

    if iterable:
        if isinstance(iterable, QuerySet):
            total = iterable.count()
        else:
            total = len(iterable)
        items = iterable[(page - 1) * per_page:page * per_page]

    total_pages = int(ceil(total / (per_page * 1.0)))

    if page > total_pages:
        pages = []
    elif total_pages <= 2 * adjacents:
        pages = range(1, total_pages + 1)
    else:
        if page <= adjacents:
            start = 1
        else:
            if total_pages - page < adjacents:
                start = total_pages - 2 * adjacents
            else:
                start = page - adjacents
        increment = 2 * adjacents + 1
        pages = range(start, start + increment)

    return {
        'page': page,
        'pages': pages,
        'total': total,
        'total_pages': total_pages,
        'items': items,
    }