Consider a store where items have prices per unit but also volume prices. For example, apples may be $1.00 each or 4 for $3.00.
Implement a point-of-sale scanning API that accepts an arbitrary ordering of products (similar to what would happen at a checkout line) and then returns the correct total price for an entire shopping cart based on the per unit prices or the volume prices as applicable.
Here are the products listed by code and the prices to use (there is no sales tax):
| Product Code | Price |
|---|---|
| A | $2 each or 4 for $7 |
| B | $12 |
| C | $1.25 each or $6 for a six-pack |
| D | $.15 |
There should be a top level point of sale terminal service object that looks something like the pseudo-code below. You are free to design and implement the rest of the code however you wish, including how you specify the prices in the system:
terminal.setPricing(...)
terminal.scan("A")
terminal.scan("C")
... etc...
result = terminal.total
Here are the minimal inputs you should use for your test cases.
- Scan these items in this order: ABCDABAA; Verify the total price is $32.40.
- Scan these items in this order: CCCCCCC; Verify the total price is $7.25.
- Scan these items in this order: ABCD; Verify the total price is $15.40.
sbt run
sbt test
Purely functional solution, using cats, cats-effect and console4cats libs.
State is handled and mutated safely with Ref.
A sample Demo application is provided.