PyLTI1p3 1.4.0

LTI 1.3 Advantage Tool implementation in Python

LTI 1.3 Advantage Tool implementation in Python
===============================================

.. image:: https://img.shields.io/pypi/v/PyLTI1p3
:scale: 100%
:target: https://pypi.python.org/pypi/PyLTI1p3
:alt: PyPI

.. image:: https://img.shields.io/pypi/pyversions/PyLTI1p3
:scale: 100%
:target: https://www.python.org/
:alt: Python

.. image:: https://travis-ci.org/dmitry-viskov/pylti1.3.svg?branch=master
:scale: 100%
:target: https://travis-ci.org/dmitry-viskov/pylti1.3
:alt: Build Status

.. image:: https://img.shields.io/github/license/dmitry-viskov/pylti1.3
:scale: 100%
:target: https://raw.githubusercontent.com/dmitry-viskov/pylti1.3/master/LICENSE
:alt: MIT


This project is a Python implementation of the similar `PHP tool`_.
Library contains adapters for usage from Django and Flask web frameworks but there is no difficulty to adapt it to other frameworks: you should just re-implement ``OIDCLogin`` and ``MessageLaunch`` classes as it is already done in existing adapters.

.. _PHP tool: https://github.com/IMSGlobal/lti-1-3-php-library

Usage examples
==============

Django: https://github.com/dmitry-viskov/pylti1.3-django-example

Flask: https://github.com/dmitry-viskov/pylti1.3-flask-example

Configuration
=============

To configure your own tool you may use built-in adapters:

.. code-block:: python

from pylti1p3.tool_config import
tool_conf = ToolConfJsonFile('path/to/json')

from pylti1p3.tool_config import ToolConfDict
settings = {
"<issuer_1>": { },
"<issuer_2>": { }
}
private_key = '...'
tool_conf = ToolConfDict(settings)
tool_conf.set_private_key(iss, private_key)

or create your own implementation. The ``pylti1p3.tool_config.ToolConfAbstract`` interface must be fully implemented for this to work.

Usage with Django
=================

Open Id Connect Login Request
-----------------------------

LTI 1.3 uses a modified version of the OpenId Connect third party initiate login flow. This means that to do an LTI 1.3 launch, you must first receive a login initialization request and return to the platform.

To handle this request, you must first create a new ``OIDCLogin`` (or ``DjangoOIDCLogin``) object:

.. code-block:: python

from pylti1p3.contrib.django import DjangoOIDCLogin

oidc_login = DjangoOIDCLogin(request, tool_conf)

Now you must configure your login request with a return url (this must be preconfigured and white-listed on the tool).
If a redirect url is not given or the registration does not exist an ``pylti1p3.exception.OIDC_Exception`` will be thrown.

.. code-block:: python

try:
oidc_login.redirect(get_launch_url(request))
except OIDC_Exception:
# display error page
log.error('Error doing OIDC login')

With the redirect, we can now redirect the user back to the tool.
There are three ways to do this:

This will add a HTTP 302 location header:

.. code-block:: python

oidc_login.redirect(get_launch_url(request))

This will display some javascript to do the redirect instead of using a HTTP 302:

.. code-block:: python

oidc_login.redirect(get_launch_url(request), js_redirect=True)

You can also get the url you need to redirect to, with all the necessary query parameters (if you would prefer to redirect in a custom way):

.. code-block:: python

redirect_obj = oidc_login.get_redirect_object()
redirect_url = redirect_obj.get_redirect_url()

Redirect is done, we can move onto the launch.

LTI Message Launches
--------------------

Now that we have done the OIDC log the platform will launch back to the tool. To handle this request, first we need to create a new ``MessageLaunch`` (or ``DjangoMessageLaunch``) object.

.. code-block:: python

message_launch = DjangoMessageLaunch(request, tool_conf)

Once we have the message launch, we can validate it. Validation is transparent - it's done once before you try to access the message body:

.. code-block:: python

try:
launch_data = message_launch.get_launch_data()
except LtiException:
log.error('Launch validation failed')

You may do it more explicitly:

.. code-block:: python

try:
launch_data = message_launch.set_auto_validation(enable=False).validate()
except LtiException:
log.error('Launch validation failed')

Now we know the launch is valid we can find out more information about the launch.

Check if we have a resource launch or a deep linking launch:

.. code-block:: python

if message_launch.is_resource_launch():
# Resource Launch!
elif message_launch.is_deep_link_launch():
# Deep Linking Launch!
else:
# Unknown launch type

Check which services we have access to:

.. code-block:: python

if message_launch.has_ags():
# Has Assignments and Grades Service
if message_launch.has_nrps():
# Has Names and Roles Service

Accessing Cached Launch Requests
--------------------------------

It is likely that you will want to refer back to a launch later during subsequent requests. This is done using the launch id to identify a cached request. The launch id can be found using:

.. code-block:: python

launch_id = message_launch.get_launch_id()

Once you have the launch id, you can link it to your session and pass it along as a query parameter.

**Make sure you check the launch id against the user session to prevent someone from making actions on another person's launch.**

Retrieving a launch using the launch id can be done using:

.. code-block:: python

message_launch = DjangoMessageLaunch.from_cache(launch_id, request, tool_conf)

Once retrieved, you can call any of the methods on the launch object as normal, e.g.

.. code-block:: python

if message_launch.has_ags():
# Has Assignments and Grades Service

Deep Linking Responses
----------------------

If you receive a deep linking launch, it is very likely that you are going to want to respond to the deep linking request with resources for the platform.

To create a deep link response you will need to get the deep link for the current launch:

.. code-block:: python

deep_link = message_launch.get_deep_link()

Now we need to create ``pylti1p3.deep_link_resource.DeepLinkResource`` to return:

.. code-block:: python

resource = DeepLinkResource()
resource.set_url("https://my.tool/launch")\
.set_custom_params({'my_param': my_param})\
.set_title('My Resource')

Everything is set to return the resource to the platform. There are two methods of doing this.

The following method will output the html for an aut-posting form for you.

.. code-block:: python

deep_link.output_response_form([resource1, resource2])

Alternatively you can just request the signed JWT that will need posting back to the platform by calling.

.. code-block:: python

deep_link.get_response_jwt([resource1, resource2])

Names and Roles Service
-----------------------

Before using names and roles you should check that you have access to it:

.. code-block:: python

if not message_launch.has_nrps():
raise Exception("Don't have names and roles!")

Once we know we can access it, we can get an instance of the service from the launch.

.. code-block:: python

nrps = message_launch.get_nrps()

From the service we can get list of all members by calling:

.. code-block:: python

members = nrps.get_members()

Assignments and Grades Service
------------------------------

Before using assignments and grades you should check that you have access to it:

.. code-block:: python

if not launch.has_ags():
raise Exception("Don't have assignments and grades!")

Once we know we can access it, we can get an instance of the service from the launch:

.. code-block:: python

ags = launch.get_ags()

To pass a grade back to the platform, you will need to create a ``pylti1p3.grade.Grade`` object and populate it with the necessary information:

.. code-block:: python

gr = Grade()
gr.set_score_given(earned_score)\
.set_score_maximum(100)\
.set_timestamp(datetime.datetime.utcnow().strftime('%Y-%m-%dT%H:%M:%S+0000'))\
.set_activity_progress('Completed')\
.set_grading_progress('FullyGraded')\
.set_user_id(external_user_id)

To send the grade to the platform we can call:

.. code-block:: python

ags.put_grade(gr)

This will put the grade into the default provided lineitem. If no default lineitem exists it will create one.

If you want to send multiple types of grade back, that can be done by specifying a ``pylti1p3.lineitem.LineItem``:

.. code-block:: python

line_item = LineItem()
line_item.set_tag('grade')\
.set_score_maximum(100)\
.set_label('Grade')

ags.put_grade(gr, line_item);

If a lineitem with the same ``tag`` exists, that lineitem will be used, otherwise a new lineitem will be created.

Usage with Flask
================

Open Id Connect Login Request
-----------------------------

This is draft of API endpoint. Wrap it in library of your choice.

Create ``FlaskRequest`` adapter. Then create instance of ``FlaskOIDCLogin``. ``redirect`` method will return instance of ``werkzeug.wrappers.Response`` that points to LTI platform if login was successful. Handle exceptions.

.. code-block:: python

from flask import request, session
from pylti1p3.flask_adapter import (FlaskRequest, FlaskOIDCLogin)

def login(request_params_dict):

tool_conf = ... # See Configuration chapter above

# FlaskRequest by default use flask.request and flask.session
# so in this case you may define request object without any arguments:

request = FlaskRequest()

# in case of using different request object (for example webargs or something like this)
# you may pass your own values:

request = FlaskRequest(
cookies=request.cookies,
session=session,
request_data=request_params_dict,
request_is_secure=request.is_secure
)

oidc_login = FlaskOIDCLogin(
request=request,
tool_config=tool_conf,
session_service=FlaskSessionService(request),
cookie_service=FlaskCookieService(request)
)

return oidc_login.redirect(request.get_param('target_link_uri'))

LTI Message Launches
--------------------

This is draft of API endpoint. Wrap it in library of your choice.

Create ``FlaskRequest`` adapter. Then create instance of ``FlaskMessageLaunch``. It lets you access data from LTI launch message if launch was successful. Handle exceptions.

.. code-block:: python

from flask import request, session
from werkzeug.utils import redirect
from pylti1p3.flask_adapter import (FlaskRequest, FlaskMessageLaunch)

def launch(request_params_dict):

tool_conf = ... # See Configuration chapter above

request = FlaskRequest()

# or

request = FlaskRequest(
cookies=...,
session=...,
request_data=...,
request_is_secure=...
)

message_launch = FlaskMessageLaunch(
request=request,
tool_config=tool_conf
)

email = message_launch.get_launch_data().get('email')

# Place your user creation/update/login logic
# and redirect to tool content here