flaskbb/flaskbb/utils/query.py

# -*- coding: utf-8 -*-
"""
    flaskbb.utils.query
    ~~~~~~~~~~~~~~~~~~~

    This module holds the query classes that are used by flaskbb

    :copyright: (c) 2013 by the FlaskBB Team.
    :license: BSD, see LICENSE for more details.
"""
from math import ceil

from flask import abort
from flask.ext.sqlalchemy import BaseQuery


class Pagination(object):
    """Internal helper class returned by :meth:`BaseQuery.paginate`.  You
    can also construct it from any other SQLAlchemy query object if you are
    working with other libraries.  Additionally it is possible to pass `None`
    as query object in which case the :meth:`prev` and :meth:`next` will
    no longer work.
    """

    def __init__(self, query, page, per_page, total, items, add_none):
        #: the unlimited query object that was used to create this
        #: pagination object.
        self.query = query
        #: the current page number (1 indexed)
        self.page = page
        #: the number of items to be displayed on a page.
        self.per_page = per_page
        #: the total number of items matching the query
        self.total = total
        #: the items for the current page
        if add_none:
            self.items = [(item, None) for item in items]
        else:
            self.items = items

    @property
    def pages(self):
        """The total number of pages"""
        if self.per_page == 0:
            pages = 0
        else:
            pages = int(ceil(self.total / float(self.per_page)))
        return pages

    def prev(self, error_out=False):
        """Returns a :class:`Pagination` object for the previous page."""
        assert self.query is not None, 'a query object is required ' \
                                       'for this method to work'
        return self.query.paginate(self.page - 1, self.per_page, error_out,
                                   add_none)

    @property
    def prev_num(self):
        """Number of the previous page."""
        return self.page - 1

    @property
    def has_prev(self):
        """True if a previous page exists"""
        return self.page > 1

    def next(self, error_out=False):
        """Returns a :class:`Pagination` object for the next page."""
        assert self.query is not None, 'a query object is required ' \
                                       'for this method to work'
        return self.query.paginate(self.page + 1, self.per_page, error_out,
                                   add_none)

    @property
    def has_next(self):
        """True if a next page exists."""
        return self.page < self.pages

    @property
    def next_num(self):
        """Number of the next page"""
        return self.page + 1

    def iter_pages(self, left_edge=2, left_current=2,
                   right_current=5, right_edge=2):
        """Iterates over the page numbers in the pagination.  The four
        parameters control the thresholds how many numbers should be produced
        from the sides.  Skipped page numbers are represented as `None`.
        This is how you could render such a pagination in the templates:

        .. sourcecode:: html+jinja

            {% macro render_pagination(pagination, endpoint) %}
              <div class=pagination>
              {%- for page in pagination.iter_pages() %}
                {% if page %}
                  {% if page != pagination.page %}
                    <a href="{{ url_for(endpoint, page=page) }}">{{ page }}</a>
                  {% else %}
                    <strong>{{ page }}</strong>
                  {% endif %}
                {% else %}
                  <span class=ellipsis>…</span>
                {% endif %}
              {%- endfor %}
              </div>
            {% endmacro %}
        """
        last = 0
        for num in xrange(1, self.pages + 1):
            if num <= left_edge or \
               (num > self.page - left_current - 1 and
                num < self.page + right_current) or \
               num > self.pages - right_edge:
                if last + 1 != num:
                    yield None
                yield num
                last = num


class TopicQuery(BaseQuery):
    def paginate(self, page, per_page=20, error_out=True, add_none=False):
        """Returns `per_page` items from page `page`.  By default it will
        abort with 404 if no items were found and the page was larger than
        1.  This behavor can be disabled by setting `error_out` to `False`.

        Returns an :class:`Pagination` object.
        """
        if error_out and page < 1:
            abort(404)
        items = self.limit(per_page).offset((page - 1) * per_page).all()
        if not items and page != 1 and error_out:
            abort(404)

        # No need to count if we're on the first page and there are fewer
        # items than we expected.
        if page == 1 and len(items) < per_page:
            total = len(items)
        else:
            total = self.order_by(None).count()

        return Pagination(self, page, per_page, total, items, add_none)