~azzar1/unity/add-show-desktop-key

# 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, Nick Chadwick

import cgi

import functools

import inspect

import os

import urlparse

import cjson

import genshi.template

from ivle.webapp.base.views import BaseView

from ivle.webapp.base.xhtml import GenshiLoaderMixin

from ivle.webapp.errors import BadRequest, MethodNotAllowed, Unauthorized

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 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 authorize(self, req):

        return True # Real authz performed in render().

    def authorize_method(self, req, op):

        if not hasattr(op, '_rest_api_permission'):

            raise Unauthorized()

        if (op._rest_api_permission not in

            self.get_permissions(req.user, req.config)):

            raise Unauthorized()

    def convert_bool(self, value):

        if value in ('True', 'true', True):

            return True

        elif value in ('False', 'false', False):

            return False

        else:

            raise BadRequest()

    def render(self, req):

        if req.method not in self._allowed_methods:

            raise MethodNotAllowed(allowed=self._allowed_methods)

        if req.method == 'GET':

            qargs = dict(cgi.parse_qsl(

                urlparse.urlparse(req.unparsed_uri).query,

                keep_blank_values=1))

            if 'ivle.op' in qargs:

                outjson = self._named_operation(req, qargs, readonly=True)

            else:

                self.authorize_method(req, self.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'):

            self.authorize_method(req, self.PATCH)

            try:

                input = cjson.decode(req.read())

            except cjson.DecodeError:

                raise BadRequest('Invalid JSON data')

            outjson = self.PATCH(req, input)

        elif req.method == 'PUT':

            self.authorize_method(req, self.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.

            data = req.read()

            opargs = dict(cgi.parse_qsl(data, keep_blank_values=1))

            outjson = self._named_operation(req, opargs)

        req.content_type = self.content_type

        self.write_json(req, outjson)

    #This is a separate function to allow additional data to be passed through

    def write_json(self, req, outjson):

        if outjson is not None:

            req.write(cjson.encode(outjson))

            req.write("\n")

    def _named_operation(self, req, opargs, readonly=False):

        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.')

        if readonly and op._rest_api_write_operation:

            raise BadRequest('POST required for write operation.')

        self.authorize_method(req, op)

        # 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))

        return op(req, **opargs)

class XHTMLRESTView(GenshiLoaderMixin, JSONRESTView):

    """A special type of RESTView which takes enhances the standard JSON

    with genshi XHTML functions.

    XHTMLRESTViews should have a template, which is rendered using their

    context. This is returned in the JSON as 'html'"""

    template = None

    ctx = genshi.template.Context()

    def render_fragment(self):

        if self.template is None:

            raise NotImplementedError()

        rest_template = os.path.join(os.path.dirname(

                inspect.getmodule(self).__file__), self.template)

        tmpl = self._loader.load(rest_template)

        return tmpl.generate(self.ctx).render('xhtml', doctype='xhtml')

    # This renders the template and adds it to the json

    def write_json(self, req, outjson):

        outjson["html"] = self.render_fragment()

        req.write(cjson.encode(outjson))

        req.write("\n")

class _named_operation(object):

    '''Declare a function to be accessible to HTTP users via the REST API.

    '''

    def __init__(self, write_operation, permission):

        self.write_operation = write_operation

        self.permission = permission

    def __call__(self, func):

        func._rest_api_callable = True

        func._rest_api_write_operation = self.write_operation

        func._rest_api_permission = self.permission

        return func

write_operation = functools.partial(_named_operation, True)

read_operation = functools.partial(_named_operation, False)

class require_permission(object):

    '''Declare the permission required for use of a method via the REST API.

    '''

    def __init__(self, permission):

        self.permission = permission

    def __call__(self, func):

        func._rest_api_permission = self.permission

        return func