Form3 Take Home Exercise

Technical decisions

• I've started the task discovery from API doc
• What's out of scope by the task def:
  • We don't need to provide an authorisation to access Fake API
  • We cannot use swagger autogen tool
  • We need to use low-level HTTP communication (net/http)
• We need to introduce Create, Fetch, List and Delete operations for accounts
• We need to keep things aligned, so we will introduce the sameish naming convention for client library methods
• The API provides one extra endpoint Patch, we don't need to introduce it
• I've started provided docker env
• I manually checked if all required endpoints are here and can be used
  • Delete does not behave as expected, it basically returns always 200 even for non-existent version
  • Patch endpoint does not exist
• I've updated the docker tag to latest and checked again - nothing changed for previous bullet point
• I personally prefer start from data model
  • There I found documentation
  • There are some small inconsistencies on required fields
• I've added /cmd/form3/models folder for all models
• File models/account.go contains a detailed defintion for account, reversed engineered from YAML. It will be useful for Create (marshall/unmarshall) and Fetch (unmarshall) operations
  • The account definition in YAML is quite big and we need to limit the complexity
  • I took only relevant for the first version set of fields
• File models/accounts.go contains an account collection definition for List operation, actually it is only an array of models/account.go entities
• For List endpoint we need to introduce only pagination, so we added models/pagination.go for pager definition - it contains two fields - Number (default 0), Size (default 100)
• I played with Postman, and discover HATEOAS media links, so I've added models/links.go
• From perspective of production readiness I can mention:
  • It should have all meaningful unit tests
  • It should have all meaningful e2e tests
  • It should be easily extensible
    • We need to keep SRP principle applied - so we try to keep logic separated
    • New features for entity management should be simple and straighforward
  • It should log all important steps
• The idea of pluggable API can be introduced via interfaces
  • So we added cmd/form3/form3.go which contains the API aggregator

type Form3 struct {
  Account Account.ClientInterface
}

func New(host string, timeout time.Duration) *Form3 {
  return &Form3{
    Account: Account.NewClient(host, timeout),
  }
}

And the aggregator will be called in the unified way

f3 := Form3.New(os.Getenv('FORM3_API'), time.Duration(5 * time.Second))

f3.Account.Create(...)

We can extend this aggregator in the future

type Form3 struct {
  Account Account.ClientInterface
  Claim Claim.ClientInterface
  Mandate Mandate.ClientInterface
}

func New(host string, timeout time.Duration) *Form3 {
  return &Form3{
    Account: Account.NewClient(host, timeout),
    Claim: Claim.NewClient(host, timeout),
    Mandate: Mandate.NewClient(host, timeout),
  }
}

f3.Mandate.Create(...)
f3.Claim.List(...)

• We need to follow 12-factor app principles
  • We introduced automatic tests for docker image, check CMD
  • We inject FORM3_API via env
• We keep models simple, without any logic

What is left/can be improved

• Implement complex validation rules for all countries (currently done only for GB, take a look in the validation folder and docs)
• Implement IBAN generation
• Implement PATCH operation
• OrganisationID must be injected into Form3
• Models shared between different domains
• Add CI/CD

Tech stack

• Golang 1.14
• UUID from Google
• validation.v9 library with tag-based validation
• testify/assert & testify/mock

Setup

0. Install docker and docker-compose
1. Run docker-compose up
2. Press Ctrl-C after test review

Project structure

\_ cmd/form3
    \_ account      # account client interface implementation
    \_ common       # common helpers
    \_ models       # shared models
    \_ test         # test helpers
    \_ validation   # validators
    form3           # API aggregator
\_ scripts
    \_ db           # db init scripts
    \_ test         # JSON fixture folder
Makefile            # useful shortcuts