Add this line to your application's Gemfile:

gem 'salestation'

And then execute:

$ bundle

First include Salestation::Web. This will provide a method called process to execute a request and Responses module for return codes.

class Webapp < Sinatra::Base
  include Salestation::Web.new
end

Create Salestation application:

  def app
    @_app ||= Salestation::App.new(env: ENVIRONMENT)
  end

Define a route

post '/hello/:name' do
  process(
    HelloUser.call(app.create_request(
      name: params['name']
    )).map(Responses.to_ok)
  )
end

Define chain

class HelloUser
  def self.call(request)
    request >> upcase >> format
  end

  def self.upcase
    -> (request) do
      input.with_input(name: input.fetch(:name).upcase)
    end
  end

  def self.format
    -> (request) do
      name = request.input.fetch(:name)
      Deterministic::Result::Success(message: "Hello #{name}")
    end
  end
end

Salestation allows and recommends you to define your own custom errors. This is useful when your app has error classes that are not general enough for the salestation library.

  include Salestation::Web.new(errors: {
    CustomError => -> (error) { CustomResponse.new(error) }
  })

If you need to specify additional error fields you can use from method. from accepts base error on which the rest of the response is built. Base error must be a hash or implement to_h method.

Example:

App::Errors::Conflict.from({details: 'details'}, message: 'message', debug_message: 'debug_message')

Response:

{
  "details": "details",
  "message": "message",
  "debug_message": "debug_message"
}

Salestation provides extractors to fetch parameters from the request and pass them to the chain. Available extractors are BodyParamExtractor, QueryParamExtractor, ConstantInput, HeadersExtractor. Multiple extractors can be merged together. If two or more extractors use the same key, the value will be from the last extractor in the merge chain.

coercions can optionally be provided to BodyParamExtractor and QueryParamExtractor. These can be used to transform the values of the extracted parameters.

ParamExtractor, which is also used by BodyParamExtractor and QueryParamExtractor, extracts only the content of such root level keys that are specified when creating the extractor instance. All other root level keys are discarded. Everything inside the whitelisted root level keys is automatically whitelisted.

Define a route

include Salestation::Web.new
include Salestation::Web::Extractors

APP = Salestation::App.new(env: {})

def create_app_request
  -> (input) { App.create_request(input) }
end

post '/hello/:name' do |name|
  extractor = BodyParamExtractor[:age]
    .merge(ConstantInput[name: name])
    .merge(HeadersExtractor[
      'accept' => :accept,
      'content-type' => :content_type,
      'x-my-value' => :my_value
    ])
    .coerce(age: ->(age) { age.to_s })

  validate_input = Salestation::Web::InputValidator[
    accept: Salestation::Web::InputValidators::AcceptHeader['application/json', 'application/xml'],
    content_type: Salestation::Web::InputValidators::ContentTypeHeader['application/json'],
    my_value: lambda do |my_value|
      if my_value == 'foo'
        Deterministic::Result::Success(nil)
      else
        Deterministic::Result::Failure('invalid value')
      end
    end
  ]

  response = extractor.call(request)
    .map(validate_input)
    .map(create_app_request)
    .map(HelloUser)
    .map(Responses.to_ok)

  process(response)
end

Salestation provides a rack logging middleware which can be used to log structured objects.

class Webapp < Sinatra::Base
  # ...
  use Salestation::Web::RequestLogger, my_logger
end

You can configure per-request fields by defining salestation.request_logger.fields in sinatra env:

  def my_handler(env)
    env['salestation.request_logger.fields'] = { foo: 'bar' }
    # ...
  end

Salestation provides a StatsD middleware which can be used record request execution time. A distribution call with elapsed seconds is made to the provided StatsD instance with path, method, status and status_class tags.

class Webapp < Sinatra::Base
  # ...
  use Salestation::Web::StatsdMiddleware,
    Statsd.new(host, port),
    metric: 'my_service.response.time'
end

You can configure per-request tags by defining salestation.statsd.tags in sinatra env:

  def my_handler(env)
    env['salestation.statsd.tags'] = ['foo:bar']
    # ...
  end

To use Salestation RSpec matchers you first need to include them:

require 'salestation/rspec'

RSpec.configure do |config|
  config.include Salestation::RSpec::Matchers
end

After that it's possible to match against error results like this:

expect(result).to be_failure
  .with_conflict
  .containing(message: 'Oh noes')

See lib/salestation/rspec.rb for more examples.

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. A new version is created when a change is merged into the master branch that changes the version number in salestation.gemspec. A Github Action will create a tag for the version and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/salestation.

The gem is available as open source under the terms of the MIT License.