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# IVLE - Informatics Virtual Learning Environment
# Copyright (C) 2007-2009 The University of Melbourne
#
# 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; either version 2 of the License, or
# (at your option) any later version.
#
# 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 St, Fifth Floor, Boston, MA 02110-1301 USA
# Author: Matt Giuca, Will Grant
import cgi
import inspect
import cjson
from ivle.webapp.base.views import BaseView
from ivle.webapp.errors import BadRequest, MethodNotAllowed
class RESTView(BaseView):
"""
A view which provides a RESTful interface. The content type is
unspecified (see JSONRESTView for a specific content type).
"""
content_type = "application/octet-stream"
def __init__(self, req, *args, **kwargs):
for key in kwargs:
setattr(self, key, kwargs[key])
def render(self, req):
raise NotImplementedError()
class JSONRESTView(RESTView):
"""
A special case of RESTView which deals entirely in JSON.
"""
content_type = "application/json"
_allowed_methods = property(
lambda self: [m for m in ('GET', 'PUT', 'PATCH')
if hasattr(self, m)] + ['POST'])
def render(self, req):
if req.method not in self._allowed_methods:
raise MethodNotAllowed(allowed=self._allowed_methods)
if req.method == 'GET':
outjson = self.GET(req)
# Since PATCH isn't yet an official HTTP method, we allow users to
# turn a PUT into a PATCH by supplying a special header.
elif req.method == 'PATCH' or (req.method == 'PUT' and
'X-IVLE-Patch-Semantics' in req.headers_in and
req.headers_in['X-IVLE-Patch-Semantics'].lower() == 'yes'):
try:
input = cjson.decode(req.read())
except cjson.DecodeError:
raise BadRequest('Invalid JSON data')
outjson = self.PATCH(req, input)
elif req.method == 'PUT':
try:
input = cjson.decode(req.read())
except cjson.DecodeError:
raise BadRequest('Invalid JSON data')
outjson = self.PUT(req, input)
# POST implies named operation.
elif req.method == 'POST':
# TODO: Check Content-Type and implement multipart/form-data.
opargs = dict(cgi.parse_qsl(req.read()))
try:
opname = opargs['ivle.op']
del opargs['ivle.op']
except KeyError:
raise BadRequest('No named operation specified.')
try:
op = getattr(self, opname)
except AttributeError:
raise BadRequest('Invalid named operation.')
if not hasattr(op, '_rest_api_callable') or \
not op._rest_api_callable:
raise BadRequest('Invalid named operation.')
# Find any missing arguments, except for the first two (self, req)
(args, vaargs, varkw, defaults) = inspect.getargspec(op)
args = args[2:]
# To find missing arguments, we eliminate the provided arguments
# from the set of remaining function signature arguments. If the
# remaining signature arguments are in the args[-len(defaults):],
# we are OK.
unspec = set(args) - set(opargs.keys())
if unspec and not defaults:
raise BadRequest('Missing arguments: ' + ', '.join(unspec))
unspec = [k for k in unspec if k not in args[-len(defaults):]]
if unspec:
raise BadRequest('Missing arguments: ' + ', '.join(unspec))
# We have extra arguments if the are no match args in the function
# signature, AND there is no **.
extra = set(opargs.keys()) - set(args)
if extra and not varkw:
raise BadRequest('Extra arguments: ' + ', '.join(extra))
outjson = op(req, **opargs)
req.content_type = self.content_type
if outjson is not None:
req.write(cjson.encode(outjson))
req.write("\n")
def named_operation(meth):
'''Declare a function to be accessible to HTTP users via the REST API.
'''
meth._rest_api_callable = True
return meth
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