from oauth.oauth import OAuthRequest, OAuthServer, build_authenticate_header,\
    OAuthSignatureMethod_PLAINTEXT, OAuthSignatureMethod_HMAC_SHA1

from django.conf import settings
from django.http import HttpResponse

from stores import DataStore

OAUTH_REALM_KEY_NAME = getattr(settings, 'OAUTH_REALM_KEY_NAME', '')
OAUTH_SIGNATURE_METHODS = getattr(settings, 'OAUTH_SIGNATURE_METHODS', ['plaintext', 'hmac-sha1'])

def initialize_server_request(request):
    """Shortcut for initialization."""
    # Django converts Authorization header in HTTP_AUTHORIZATION
    # Warning: it doesn't happen in tests but it's useful, do not remove!
    auth_header = {}
    if 'Authorization' in request.META:
        auth_header = {'Authorization': request.META['Authorization']}
    elif 'HTTP_AUTHORIZATION' in request.META:
        auth_header =  {'Authorization': request.META['HTTP_AUTHORIZATION']}
    
    parameters = dict(request.REQUEST.items())
    oauth_request = OAuthRequest.from_request(request.method, 
                                              request.build_absolute_uri(), 
                                              headers=auth_header,
                                              parameters=parameters,
                                              query_string=request.META.get('QUERY_STRING', ''))
    if oauth_request:
        oauth_server = OAuthServer(DataStore(oauth_request))
        if 'plaintext' in OAUTH_SIGNATURE_METHODS:
            oauth_server.add_signature_method(OAuthSignatureMethod_PLAINTEXT())
        if 'hmac-sha1' in OAUTH_SIGNATURE_METHODS:
            oauth_server.add_signature_method(OAuthSignatureMethod_HMAC_SHA1())
    else:
        oauth_server = None
    return oauth_server, oauth_request

def send_oauth_error(err=None):
    """Shortcut for sending an error."""
    # send a 401 error
    response = HttpResponse(err.message.encode('utf-8'), mimetype="text/plain")
    response.status_code = 401
    # return the authenticate header
    header = build_authenticate_header(realm=OAUTH_REALM_KEY_NAME)
    for k, v in header.iteritems():
        response[k] = v
    return response