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pagination.py
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pagination.py
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# -*- coding: utf-8 -*-
#
# This file is part of Invenio.
# Copyright (C) 2014 CERN.
#
# Invenio is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation; either version 2 of the
# License, or (at your option) any later version.
#
# Invenio is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Invenio; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
"""Restful pagination."""
from flask import request, url_for
from invenio.utils.pagination import Pagination as InvenioPagination
from .errors import InvalidPageError
class RestfulPaginationMixIn(object):
"""Provide implementaion methods :meth:`link_header` and :meth:`links`."""
def link_header(self, **kwargs):
"""Return tuple that can be used in response header."""
links = self.links(**kwargs)
keys = ("first", "prev", "next", "last")
links_string = ",".join([links[key] for key in keys if key in links])
return ('Link', links_string)
def links(self, endpoint=None, args=None):
"""Generate links for the headers.
:param endpoint: the URL endpoint
:param args: the arguments of request
:param count: the total number of items
"""
if not endpoint:
endpoint = request.endpoint
if not args:
args = request.args
links = {}
link_template = '<{}>; rel="{}"'
# arguments to stick to the URL
url_args = {}
# url_args['page'] will be updated for every link
url_args['page'] = 1
url_args['per_page'] = self.per_page
# generate link for rel first
links['first'] = link_template.format(
url_for(endpoint, **url_args), "first"
)
# generate link for prev if it exists
if self.has_prev:
url_args['page'] = self.page - 1
links['prev'] = link_template.format(
url_for(endpoint, **url_args), "prev"
)
# generate link for next if it exists
if self.has_next:
url_args['page'] = self.page + 1
links['next'] = link_template.format(
url_for(endpoint, **url_args), "next"
)
# generate link for last
url_args['page'] = self.pages
links['last'] = link_template.format(
url_for(endpoint, **url_args), "last"
)
return links
class SQLAlchemyPaginationHelper(object):
"""Wrap SQLAlchemy query `paginate` method."""
def __init__(self, query, page, per_page):
"""Initialize pagination property.
:param query: query object from SQLAlchemy
"""
self.query = query
self.page = page
self.per_page = per_page
self.pagination = self.query.paginate(self.page, self.per_page, False)
class RestfulSQLAlchemyPagination(SQLAlchemyPaginationHelper,
RestfulPaginationMixIn):
"""Implement Restful pagination for SQLAlchemy model."""
@property
def items(self):
"""Return found items."""
return self.pagination.items
@property
def pages(self):
"""Return number of pages."""
return self.pagination.pages
@property
def has_next(self):
"""Return `True` if has next page otherwise return `False`."""
return self.pagination.has_next
@property
def has_prev(self):
"""Return `True` if has previous page otherwise return `False`."""
return self.pagination.has_prev
class RestfulPagination(InvenioPagination, RestfulPaginationMixIn):
"""Implement Restful pagination for list of data."""
def __init__(self, page, per_page, total_count, validate=True):
super(RestfulPagination, self).__init__(page, per_page, total_count)
if validate:
self.validate()
def validate(self):
"""Validate the range of page and per_page."""
if self.per_page < 0:
error_msg = (
"Invalid per_page argument ('{0}'). Number of items "
"per pages must be positive integer.".format(self.per_page)
)
raise InvalidPageError(error_msg)
if self.page < 0 or self.page > self.pages:
error_msg = "Invalid page number ('{0}').".format(self.page)
raise InvalidPageError(error_msg)
def slice(self, items):
"""Return items on current page."""
return items[(self.page - 1) * self.per_page:self.page * self.per_page]

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