TechnicalTask

Quick start

To develop/run the server locally, there is a development environment defined in docker-compose-yaml that can be used. This will create 2 containers:

• A development environment (defined in the Dockerfile under the dev target)
• A Postgres service to use

To spin up the dev env

make dev-up

To enter the dev env

make dev-shell

To teardown the dev env

make dev-down

Alternatively, docker compose up -d and docker compose exec transaction-dev sh can be used instead of make dev-up and make dev-shell.

Start the server

From within the dev env:

To start the server, first build the project using the Make target...

make build

This will build the project in the dist directory within the container. The server can then be started using...

./dist/transactionServer

The server will then be running and listening for request on localhost:3000.

Sending requests

The compose file used to create the dev env environment exposes the containers 3000 port to the host, so requests can be made either within the dev container or on the host machine.

For example getting an account via curl on the host machine...

curl --request GET \
  --url http://localhost:3000/accounts/018fdf82-1286-7b07-9c4b-073403bfddf4 \
  --header 'Accept: application/json, application/problem+json' | jq

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   123  100   123    0     0   9420      0 --:--:-- --:--:-- --:--:--  9461
{
  "account_id": "018fdf82-1286-7b07-9c4b-073403bfddf4",
  "document_number": "12345",
  "created_at": "2024-06-03T19:09:54.694723Z"
}

API documentation

When the server is running (either locally or in the dev container), the API documentation can be viewed on http://localhost:3000/docs.

Requests can also be made via this documentation site.

Inside the development container

The following Make targets are also available:

• make unit - Runs the unit tests
• make fmt - format the code with gofmt
• make dev-db-connect - Connect to the database via psql
• make mocks - Regenerate the mocks using mockery

Configuration

The configuration settings for running locally are stored in bench-config.toml.

The app gets its configuration settings from the a toml file that should be specified using the environment variable CONFIG_FILE. For local execution, this is set to bench-config.toml within the docker compose file.

My submission

From the instuctions given, I made the following assumptions when creating the API:

• There is a 1:1 mapping between accounts/customers and the document number, meaning that an account cannot be created with the same document number as another account.
• When creating an account, we should also store its creation timestamp
• When requesting to create a transaction, all amounts are entered as positive integers in the lowest denomination. They are then made positive or negative based on the operation type before being stored in the database.

I decided to implement this project following clean architecture to improve the future support and flexibility of the app/API.

I have added some unit tests, although I didn't have enough time to write all the tests I would have liked, hopefully what is present gives an idea of my intentions. These test make use of mockery for generating based on the interfaces within the code (e.g. for mocking usecase or database operations).

Examples

Creating an account

curl --request POST \
  --url http://localhost:3000/accounts \
  --header 'Accept: application/json, application/problem+json' \
  --header 'Content-Type: application/json' \
  --data '{
  "document_number": "999"
}' | jq


  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   154  100   124  100    30  12493   3022 --:--:-- --:--:-- --:--:-- 17111
{
  "account_id": "018fdf9f-fb46-7891-b644-fab15dd91e23",
  "document_number": "999",
  "created_at": "2024-06-03T19:42:34.822569001Z"
}

Getting an account

curl --request GET \
  --url http://localhost:3000/accounts/018fdf9f-fb46-7891-b644-fab15dd91e23 \
  --header 'Accept: application/json, application/problem+json' | jq


  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   121  100   121    0     0  12676      0 --:--:-- --:--:-- --:--:-- 13444
{
  "account_id": "018fdf9f-fb46-7891-b644-fab15dd91e23",
  "document_number": "999",
  "created_at": "2024-06-03T19:42:34.822569Z"
}

Creating 2 transactions

curl --request POST \
  --url http://localhost:3000/transactions \
  --header 'Accept: application/json, application/problem+json' \
  --header 'Content-Type: application/json' \
  --data '{
  "account_id": "018fdf9f-fb46-7891-b644-fab15dd91e23",
  "amount": 150,
  "operation_type_id": 2
}' | jq


  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   290  100   189  100   101   6981   3730 --:--:-- --:--:-- --:--:-- 10740
{
  "transaction_id": "018fdfa1-c78b-7cba-a0fe-7b586d476edd",
  "account_id": "018fdf9f-fb46-7891-b644-fab15dd91e23",
  "operation_type": 2,
  "amount": -150,
  "event_date": "2024-06-03T19:44:32.651845417Z"
}

curl --request POST \
  --url http://localhost:3000/transactions \
  --header 'Accept: application/json, application/problem+json' \
  --header 'Content-Type: application/json' \
  --data '{
  "account_id": "018fdf9f-fb46-7891-b644-fab15dd91e23",
  "amount": 100,
  "operation_type_id": 4
}' | jq


  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   289  100   188  100   101  31639  16997 --:--:-- --:--:-- --:--:-- 57800
{
  "transaction_id": "018fdfa2-8d38-748a-b577-91cecc370e7b",
  "account_id": "018fdf9f-fb46-7891-b644-fab15dd91e23",
  "operation_type": 4,
  "amount": 100,
  "event_date": "2024-06-03T19:45:23.256302927Z"
}

Viewing the created transaction in the database

make dev-db-connect
transactions-db=# select * from transactions where account_id='018fdf9f-fb46-7891-b644-fab15dd91e23';
                  id                  |              account_id              |     operation_id     | amount |         event_time
--------------------------------------+--------------------------------------+----------------------+--------+----------------------------
 018fdfa1-c78b-7cba-a0fe-7b586d476edd | 018fdf9f-fb46-7891-b644-fab15dd91e23 | INSTALLMENT PURCHASE |   -150 | 2024-06-03 19:44:32.651845
 018fdfa2-8d38-748a-b577-91cecc370e7b | 018fdf9f-fb46-7891-b644-fab15dd91e23 | PAYMENT              |    100 | 2024-06-03 19:45:23.256302
(2 rows)