#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Flask License
#
# Copyright © 2010 by the Pallets team.
#
# Some rights reserved.

# Redistribution and use in source and binary forms of the software as well as
# documentation, with or without modification, are permitted provided that the
# following conditions are met:
#
# Redistributions of source code must retain the above copyright notice, this list of conditions
# and the following disclaimer.
# Redistributions in binary form must reproduce the above copyright notice, this list of conditions
# and the following disclaimer in the documentation and/or other materials provided with the distribution.
# Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products
# derived from this software without specific prior written permission.
#
# THIS SOFTWARE AND DOCUMENTATION IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
# INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
# IN ANY WAY OUT OF THE USE OF THIS SOFTWARE AND DOCUMENTATION, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

# http://flask.pocoo.org/snippets/62/

from __future__ import division, print_function, unicode_literals
try:
    from urllib.parse import urlparse, urljoin
except ImportError:
    from urlparse import urlparse, urljoin

from flask import request, url_for, redirect


def is_safe_url(target):
    ref_url = urlparse(request.host_url)
    test_url = urlparse(urljoin(request.host_url, target))
    return test_url.scheme in ('http', 'https') and ref_url.netloc == test_url.netloc


def get_redirect_target():
    for target in request.values.get('next'), request.referrer:
        if not target:
            continue
        if is_safe_url(target):
            return target


def redirect_back(endpoint, **values):
    target = request.form['next']
    if not target or not is_safe_url(target):
        target = url_for(endpoint, **values)
    return redirect(target)