Purpose

This is implementation of these requirements

The artifact of this solution will be a docker image with everything inside.

How to build this code

To build docker image you need to

Clone this repo and step into the repo directory.
Then run this command.

$ docker build -t shopping-cart .
Sending build context to Docker daemon  93.18kB
Step 1/3 : FROM python:alpine
 ---> 39fb80313465
Step 2/3 : COPY ./code /code
 ---> c44b673b614a
Step 3/3 : WORKDIR /code
 ---> Running in 304a7381af18
Removing intermediate container 304a7381af18
 ---> da045272a697
Successfully built da045272a697
Successfully tagged shopping-cart:latest

How to run unit tests

Using the image you've just build, execute unit tests:

$ docker run -it --rm --name shopping-cart shopping-cart python3 -m unittest discover -s tests -p '*_test.py' -v
test_constructor (checkout_test.TestCheckout) ... ok
test_scan_quantity_increments (checkout_test.TestCheckout) ... ok
test_scan_throws_exception (checkout_test.TestCheckout) ... ok
test_total_no_discount (checkout_test.TestCheckout) ... ok
test_discount_every_third_apple_tv_bought_3 (pricingrules_test.TestPricingRules) ... ok
test_discount_every_third_apple_tv_bought_4 (pricingrules_test.TestPricingRules) ... ok
test_discount_every_third_apple_tv_bought_5 (pricingrules_test.TestPricingRules) ... ok
test_discount_every_third_apple_tv_bought_7 (pricingrules_test.TestPricingRules) ... ok

----------------------------------------------------------------------
Ran 8 tests in 0.057s

OK

How to use this code

Sales Manager sets prices and pricing rules

This is done by editing YAML files inside ./config directory.

NOTE! Don't modify .yaml files inside /code/tests/config/catalog.yaml. Because they are used as unit tests fixtures and unit tests will be broken if you change them.

File `/code/config/catalog.yaml`

This files represents a set of Products

---
kind: Product
sku: ipd
name: Super iPad
price: 549.99

You can multiply and copy-paste these Product blocks as long as you keep SKUs unique.

You can set values of sku, name, price to whatever you want.

NOTE! negative prices have not been tested!

File `/code/config/pricingrules.yaml`

This file represents a set of PricingRules.

---
kind: PricingRule
name: get-three-apple-tv-for-price-of-two
description: we are going to have a 3 for 2 deal on Apple TVs. For example, if you buy 3 Apple TVs, you will pay the price of 2 only
func:
  name: discount_every_third
  params:
    appliedToSku: atv

You can copy-paste these PricingRule blocks. All func names which you use in pricingrules.yaml must be implemented in PricingRule python class.

That leads to a workflow:

Sales Manager drafts/models the pricing rule in YAML.
Then Developer can pick up the YAML file and implement corresponding function in PricingRule python class.

In the YAML it is:

possible to specify function name and parameters required for the logic of this pricing rule.
parameter appliedToSku is mandatory.
for any given appliedToSku parameter there can be only one PricingRule in the whole YAML.

Developer implements new pricing rule

See example implementation and documentation for PricingRules.discount_every_third() and Checkout.total() functions.

Example script

See run.py

suankan/shopping-cart