Level 3

The Level 3 requirements concentrate on being able to log in and out of the
application and see a page customised for the user. To meet this level you must implement another
set of procedures in the module user.py, and one more procedure in interface.py
       and then extend your
web application to allow user login.

Unit Tests

This level adds four procedures in a new users
that deal with authenticating users
and managing user sessions, and another procedure
in the interface module to access images for a given user.
They act as an interface to the users and sessions tables in
the database.   These procedures are
   implemented in the module users.py; a version of
this file with just the procedure stubs is provided for you.

1. check_login

   There is a procedure check_login in the users module
   that takes three arguments, a database connection, a user nick and a password, and returns
   True if the password is correct for this user and False otherwise.
   Note that the password is stored in the database in encrypted form.
   You can use the method db.crypt(text) to encrypt
   a password (where db is a database connection).

2. generate_session

   There is a procedure generate_session in the users module
   that takes two arguments,
   a database connection and a user nick. If the nick doesn't correspond to
   an existing user, then it returns None.  If this user doesn't already
   have an active session (an entry in the sessions table) then a new
   entry is created.   If there is an existing entry, then the existing
   session id is retrieved. The procedure then creates a cookie in the
          Bottle response with the name sessionid and a value of the session id for this user.
   The procedure returns the sessionid.

3. delete_session

   There is a procedure delete_sessions in the users module
   that takes two
   arguments, a database connection and a user nick.  The procedure
   removes all entries for this user in the sessions table. It does
   not return a value.

4. session_user

   There is a procedure session_user in the users module
   that takes
   one arguments, a database connection, and
   returns the name of the logged in user if one can be identified or
   None if not.   This is done by finding the session id from the cookie
   in the Bottle request if present, and using it to look up
   the user in the sessions table.

Functional requirements

As for level two plus:

1. Login Form

   As a visitor to the site, when I load the home page, I see a form with entry
   boxes for nick and password and a button labelled Login.

• The login form will have the id 'loginform' and
    will use fields named 'nick' and 'password'.

• The action of the login form will be   /login.

2. Logging In

   As a registered user, when I enter my user nickname (eg. Bobalooba)
   and password (bob) into the
   login form and click on the Login button, the response is a
          redirect to the main application page (/). When my browser loads
          that page I see the normal home page with the login form replaced by the message "Logged in as Bobalooba" and a button labelled Logout.

• The response generated by the successful login action
  is a redirect (302 Found) response that redirects the user
  to the home page.

• The redirect response also includes a cookie with the
  name sessionid that contains some kind of random string.

• The logout button will be in a form with id logoutform
             and have an input submit field with
  the name logout.

4. Failed Login

   As a registered user, when I enter my email address but get my password
   wrong and click on the Login button, the page I get in response contains
   a message "Login Failed, please try again".  The page also includes another
   login form.

5. Posting a Job

   As a registered user, I can fill out a form on the main
          page to create a new job listing (position), when I submit the form I am redirected
          to the main page and my new position appears in the list.

      

• The form to post a new position will have the id postform

• The action attribute for the form will be the URL /post

6. Logout Button

   As a registered user, once I have logged in, every page that I request
   contains my name and the logout button.

8. Logging Out

   As a registered user, once I have logged in, if I click on the Logout
   button in a page, the page that I get in response is the site home
   page which now doesn't have my name and again shows the login form.

    

• The response to a logout request is again a redirect
  (302 Found) response that redirects the user to the home
  page.

• When I now request the home page, I see the login form again because
               the session has been deleted.

Your Task

To achieve these requirements you will need to implement the new procedures
in interface.py and users.py and then make
use of these to extend your application to support user login and posting messages.

This may seem like a huge task but the number of features and tests listed
above are there to make your job as clear as possible.   Take each
task a step at a time and read the requirements clearly.

The following chapters in the notes may be useful:

• Session Management
  covers using cookies and a sessions table to create user sessions.

• Forms Processing describes
             handling form input in a Bottle script.

• Python and SQLite describes the
  way to send queries to SQLite and get results back.

• Web Applications with SQLite looks at using
  SQLite databases as part of an appliication.

• Testing Python
  Programs covers running unit tests.

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