# Copyright (C) 2014  Codethink Limited
#
# This program 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; version 2 of the License.
#
# This program 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 this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.


import json
import os
import urllib
import urllib2


def setup_proxy(config_filename):
    """Tell urllib2 to use a proxy for http action by lorry-controller.
    
    Load the proxy information from the JSON file given by proxy_def, then
    set urllib2's url opener to open urls via an authenticated proxy.
    
    """
    
    if not os.path.exists(config_filename):
        return
    
    with open(config_filename, 'r') as f:
        proxy = json.load(f)
        
    # set the required environment variables
    hostname = urllib.quote(proxy['hostname'])
    user = '%s:%s' % (proxy['username'], proxy['password'])
    url = '%s:%s' % (hostname, proxy['port'])
    os.environ['http_proxy'] = 'http://%s@%s' % (user, url)
    os.environ['https_proxy'] = 'https://%s@%s' % (user, url)
    
    # create a ProxyHandler
    proxies = {'http_proxy': 'http://%s@%s' % (user, url),
               'https_proxy': 'https://%s@%s' % (user, url)}
    proxy_handler = urllib2.ProxyHandler(proxies)
    
    # install an opener to use the proxy
    opener = urllib2.build_opener(proxy_handler)
    urllib2.install_opener(opener)