Homework 2 Keeping track of products

Homework 2
The Assignment
You have to construct a site for keeping track of products that are in stock. The site has two
main pages:
● A “home” page that lists products that have been “starred”.
● A “list” page where you can see and search the whole list of products, increment or
decrement their quantity, and edit the products.
Products
Each product has the following attributes:
● Name
● Description
● Quantity in stock
● Quantity sold
● Sales Price (to customer)
● Cost (to us the store owners)
● Starred (boolean)
● User who created it
The List Page
The list page must be generated with an SQLFORM.grid, and for each product (and so, for each
row) it should display:
● Name
● Quantity in stock
● Quantity sold
● Sales Price
● Cost
● Profit, computed as the product of quantity_sold * (sales_price - cost)
● A star. For the star icon, you should use Font Awesome 4.7 (4.6.3 also fine). The
master branch includes 4.6.3 already.
○ The star is black and empty if the product is “unstarred” (false), and it is full and
golden if the product is “starred” (true). Note that Font Awesome provides both
full and outline only stars.
○ Clicking on the icon if the user is logged in should toggle the status (use a
signed URL to cause the effect, similarly to how immediate delete was
implemented). Any logged in user can star/unstar a product. Clicking while not
logged in has no effect (i.e., the star is not a link in that case).
● If the user is logged in, there should be two additional buttons. These buttons need to
be implemented as buttons with signed URLs, that have effect immediately.
○ A +1 button, which increments the quantity (in stock) by one.
○ A -1 button, which decrements the quantity (in stock) by one, and increments by
one the number of products sold. The button should be enabled only if the
quantity in stock is positive; otherwise it should be grayed out.
● If the user is logged in and is the user who created the product, there should also
be two additional buttons:
○ A button to edit the item (you can use a button with a pencil icon). This leads to
a separate product edit page, where the user can edit the product. When the edit
is done, you should redirect back to the listing page.
○ A button to delete the item (you can use the trash icon). This acts immediately,
via a signed URL.
Note: We are unfortunately not working in javascript yet. So when you click on a star, or on a
[+1] button, etc, you have to implement this as following a link, that is, a GET request with a
signed URL. The receiving controller has to take the action, updating the database, and then
redirects back to the list page. This causes an ugly reloading of the page whenever one clicks
on star, +1, -1, …. This is ugly, but there is no way out right now. In a model-view-controller
framework, unless we use javascript, the only way to display a change is to display a new page.
It’s even uglier because, if you are on page 2 of a long list, clicking on (say) star would cause
the list to reload showing page 1, unless you implement some way of keeping track of the state,
which I do not require. Please put up with it, and we will have cleaner implementations once we
move to javascript.
Sample line, with abbreviated names for column headers, and not including icons for Edit and
Delete buttons:
Name Stock Sold Price Cost Profit
Yellow Socks 3 120 $20 $9 $1,320 ☆ [+1] [-1] [Edit] [Delete]
Creating Products. The list page should also let users create new products. To do so, you can
either use the create feature of SQLFORM.grid, or you can provide a separate product creation
controller and page. When creating a product, these (and only these) are the fields that can be
filled in:
● Name
● Description
● Quantity in Stock
● Sales Price
● Cost
Creating and editing products: validation
When a product is created or edited, you must check that:
● Sales price >= 0
● Cost >= 0
● Quantity in stock >= 0
Please have a look at the IS_FLOAT_IN_RANGE and IS_INT_IN_RANGE validators. You can
use 1e10 as upper bound for these.
The Home Page
The home page should display, in rectangles, all the starred products. For each product there
should be the product name and the sales price. That’s it.
Suggested Implementation Strategy
Implementation Steps
To implement the solution, I suggest that you follow the steps in the order below. Note: I have
not implemented the solution, so this is my best guess.
1. Start from the master branch of the class code; this gives you a clean slate to start the
implementation. The branch already comes with Font Awesome and stupid.css.
2. Define the database table for the products.
3. Create the SQLFORM.grid page, initially focusing on the attributes you can display
directly from the database: sales price, cost, quantity in stock, name, …
4. Add some way to create new products (a new add controller may be the simplest). If
you use a separate controller, set create=False in the SQLFORM.grid.
5. Then, add the button to star/unstar.
6. Add the buttons to +1 and -1 the quantity.
7. Add to the grid a field
8. Implement the button to edit a product.
9. Implement the button to delete a product.
10. Implement the display of the profit.
11. Implement the home page. The simplest way is to create a fixed-width div that is used to
display a product, and just generate a bunch of these divs side by side, so that the
browser will change line when it wants. All I am looking here is for you to be able to
retrieve from the db all the starred products, and display them. We will return to this
customer facing page better in the next homework.
To implement the button to star/unstar, here is a hint. Look at the implementation of the
rightback method in Lecture 6. Then:
1. In a links field, create a star that is either outline or full according to the star status
of the record.
2. Have the star link (just like the rightback button) to a toggle_star controller.
3. The toggle_star controller reads the product, toggles the state of the star in the db,
and returns with a redirect to the page that implements the SQLFORM.grid.
Database Access
Here are some methods for working with the database that may help you.
To add 1 to the quantity in stock of an item with id k, you can do as follows (see this):
p = db.product(k)
if p is None:
redirect(...)
p.quantity = p.quantity + 1 # This makes the change in memory.
p.update_record() # This writes the change to the db.
What you have to do in the toggle_star controller is quite similar.