Dynamic Web content and forms processing in Python

This function update's the user's database entry if there is one. If the user has no database entry, we create one here.

# - - -   u p d a t e D a t a b a s e

def updateDatabase ( inputs, db ):
    '''Generate a cookie if necessary; update the database.

      [ (inputs is an Inputs instance) and
        (db is a UserDatabase instance) ->
          if (inputs.userId is None) or (inputs.userId is not in db) ->
            db  :=  db with a new UserRecord whose userId is a random
                    string, whose chapterNo is 1, and whose
                    expiration time is as specified by inputs
            return that new UserRecord 
          else ->
            db  :=  db with the UserRecord for inputs.userId updated
                  as specified by inputs
            return that updated UserRecord ]
    '''

First we see if the database has a UserRecord for this user. If not, we create a new one; see Section 7.13, “newUserRecord(): Create the initial user record”.

    #-- 1 --
    # [ if db has an entry for inputs.userId ->
    #     userRecord  :=  the corresponding value
    #   else ->
    #     userRecord  :=  a new UserRecord with a randomy
    #         userId, chapterNo=1, persist=0, and expiration=0 ]
    try:
        userRecord  =  db[inputs.userId]
    except KeyError:
        userRecord  =  newUserRecord()

Adjust the chapter number up or down if this is a repeat visit, but no lower than 1 and no higher than the value specified in Section 7.6.16, “CHAPTER_COUNT”. If this is the user's first visit, neither inputs.next nor inputs.prev will be set.

    #-- 2 --
    if inputs.next:
        userRecord.chapterNo  =  min ( userRecord.chapterNo + 1,
                                       CHAPTER_COUNT )
    elif inputs.prev:
        userRecord.chapterNo  =  max ( userRecord.chapterNo - 1,
                                       1 )

Next we adjust the expiration time. See Section 7.6.14, “PERSIST_SECONDS” and Section 7.6.15, “SESSION_SECONDS”.

    #-- 3 --
    # [ now  :=  current epoch time as an integer in seconds ]
    now  =  int ( time.time() )

    #-- 4 --
    if inputs.persist:
        userRecord.persist     =  1
        userRecord.expiration  =  now + PERSIST_SECONDS
    else:
        userRecord.persist     =  0
        userRecord.expiration  =  now + SESSION_SECONDS

Place or replace the user's record in the database.

    #-- 5 --
    db[userRecord.userId]  =  userRecord

    #-- 6 --
    return userRecord