Added route decorator for Flask (using sessions)

src/imperial_doc_materials/__init__.py

 from .client import Materials
 from .courses import Course
 from .resources import Resource
+from .flask_utils import using_materials, materials_login, init_app, set_redirect_url
\ No newline at end of file

src/imperial_doc_materials/flask_utils.py

+from functools import wraps
+from typing import Optional
+from flask import abort, request, session, redirect, url_for
+from .client import Materials
+
+IMPERIAL_DOC_MATERIALS_APP_NAME = ""
+IMPERIAL_DOC_MATERIALS_URL_PREFIX = ""
+IMPERIAL_DOC_MATERIALS_REDIRECT_URL = ""
+IMPERIAL_DOC_MATERIALS_SECRET_KEY = ""
+
+SESSION_KEY_NAME = f'{IMPERIAL_DOC_MATERIALS_APP_NAME}-imperial_doc_materials_client'
+
+def init_app(app):
+    global IMPERIAL_DOC_MATERIALS_SECRET_KEY
+    global IMPERIAL_DOC_MATERIALS_APP_NAME
+    global IMPERIAL_DOC_MATERIALS_URL_PREFIX
+
+    try:
+        IMPERIAL_DOC_MATERIALS_SECRET_KEY = app.config["SECRET_KEY"]
+    except KeyError:
+        raise "Please set the SECRET_KEY for your app's config.py"
+
+    try:
+        IMPERIAL_DOC_MATERIALS_APP_NAME = app.config["APP_NAME"]
+    except KeyError:
+        raise "Please set the APP_NAME in your app's config.py"
+
+    try:
+        IMPERIAL_DOC_MATERIALS_URL_PREFIX = app.config["URL_PREFIX"]
+    except KeyError:
+        raise "Please set the URL_PREFIX in your app's config.py"
+
+def set_redirect_url(redirect_url: str):
+    global IMPERIAL_DOC_MATERIALS_REDIRECT_URL
+    IMPERIAL_DOC_MATERIALS_REDIRECT_URL = redirect_url
+
+
+def using_materials(f):
+    """
+    Decorator for a Flask route that provides access to the Materials client object
+    assuming the user is logged in.
+    """
+
+    # TODO add a token decorator
+
+    @wraps(f)
+    def session_decorator(*args, **kws):
+        if not session.get(SESSION_KEY_NAME):
+            if IMPERIAL_DOC_MATERIALS_REDIRECT_URL:
+                return redirect(IMPERIAL_DOC_MATERIALS_URL_PREFIX + str(url_for(IMPERIAL_DOC_MATERIALS_REDIRECT_URL, next=request.url)))
+            else:
+                abort(401)
+        
+        materials_client = None
+        try:
+            materials_client = Materials.from_dict(session[SESSION_KEY_NAME])
+        except:
+            if IMPERIAL_DOC_MATERIALS_REDIRECT_URL:
+                return redirect(IMPERIAL_DOC_MATERIALS_URL_PREFIX + str(url_for(IMPERIAL_DOC_MATERIALS_REDIRECT_URL, next=request.url)))
+            else:
+                abort(401)
+
+        return f(materials_client, *args, **kws)
+
+    return session_decorator
+
+
+
+def materials_login(username: str, password: str) -> Optional[Materials]:
+    """
+    Login into the Materials API with the given username and password.
+    """
+    try:
+        materials_client = Materials.create_client(username, password)
+        # TODO check whether to use session or token?
+        session[SESSION_KEY_NAME] = materials_client.get_as_dict()
+        session.modified = True
+        return materials_client
+    except:
+        return None