laranea/python-ddd: Python DDD example · GitHub

Name		Name	Last commit message	Last commit date
application		application
domain		domain
infrastructure		infrastructure
.coveragerc		.coveragerc
.gitignore		.gitignore
.travis.yml		.travis.yml
LICENSE		LICENSE
Pipfile		Pipfile
Pipfile.lock		Pipfile.lock
README.md		README.md
composition_root.py		composition_root.py
main.py		main.py
pytest.ini		pytest.ini
shell.py		shell.py

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AUCTION APPLICATION

The goal is to implement an automatic bidding system, described here: https://www.ebay.co.uk/pages/help/buy/bidding-overview.html

TODO for near future:

simple authorization (user id in request header)
first business use-case (up to three open items at the same time)
application-level exceptions for invalid commands
TESTS!!!! +code metrics + CI/CD
executing commands with immediate feedback http://blog.sapiensworks.com/post/2015/07/20/CQRS-Immediate-Feedback-Web-App
handling commands errors: application layer, business layer
command validation https://stackoverflow.com/questions/32239353/command-validation-in-ddd-with-cqrs
handling async commands (mediator pattern, asyncio)
Application-level event bus, publisher/subscriber pattern
framework agnostic integration tests??

User stories:

As a seller I can list a new item for sale. The item has the following fields: text, description, starting price
As a seller, I'm allowed to list up to 3 items at the same time
As a user I can view all the items for sale. For each item I will see: text, description, current price, minimum bidding price, a winner, all participants, auction end date
As a bidder, when placing a bid, I enter the maximum amount I am willing to pay for the item. The seller and other bidders don't know my maximum bid
As a bidder, when placing a bid, my bid must be higher than the actual price
Auction Store will automatically calculate the current price of an item based on the bids that were made
When auction ends, auction store will notify the seller by email. The email will contain the name of the winner and the sell price.
When auction ends, all losing participants will recieve an email with the information that they lost an auction.
When auction ends, the winning participant will reciewve an email with information the user has won and the price for an item.

pipenv install
pipenv shell

To run tests

pytest

To run tests in watch mode

ptw

To run the app as Falcon server

FRAMEWORK=falcon gunicorn --reload main

To run the app as Flask server

FRAMEWORK=flask gunicorn --reload main

To run application Shell:

python shell.py

Within the shell you can execute and queries and commands, i.e.:

(InteractiveConsole)
>>> c = AddItemCommand({'title': 'Fluffy bunny'})
>>> command_bus.execute(c)
<CommandResult>(ok) {}

Project structure:

context-1
  domain
    entities
    value_objects
    aggregates
    services
    repositories
    factories?
    interfaces
    events
  application
    services
  infrastructure
    ??
  tests??

context-2

context-3

di_setup
main - main entrypoint to the app

Domain artifacts

entities - mutable, identifiable, unaware of persistance
value objects - immutable, self-contained
aggregates - any transaction should modify only one aggegate at a time, 70-80% usually contain olny one entity, consistency boundary, hosts methods which will modify the aggregate
events - significant state transition, something which domain experts care about
factories - for entity construction, ubiquotous language verbs, hide construction details (Python function)
repositories - store aggregates, abstraction over persistence mehanism
context maps - mappings between concepts between bounded contexts