Cistern

Cistern helps you consistenly build your API clients and faciliates building mock support.

Usage

Service

This represents the remote service that you are wrapping. If the service name is 'foo' then a good name is 'Foo::Client'.

Requests

Requests are enumerated using the request method and required immediately via the relative path specified via request_path.

class Foo::Client < Cistern::Service
  request_path "my-foo/requests"

  request :get_bar  # require my-foo/requests/get_bar.rb
  request :get_bars # require my-foo/requests/get_bars.rb

  class Real
    def request(url)
      Net::HTTP.get(url)
    end
  end
end

A request is method defined within the context of service and mode (Real or Mock). Defining requests within the service mock class is optional.

# my-foo/requests/get_bar.rb
class Foo::Client
  class Real
    def get_bar(bar_id)
      request("http://example.org/bar/#{bar_id}")
    end
  end # Real

  # optional, but encouraged
  class Mock
    def get_bars
      # do some mock things
    end
  end # Mock
end # Foo::client

All declared requests can be listed via Cistern::Service#requests.

Foo::Client.requests # => [:get_bar, :get_bars]

Models and Collections

Models and collections have declaration semantics similar to requests. Models and collections are enumerated via model and collection respectively.

class Foo::Client < Cistern::Service
  model_path "my-foo/models"

  model :bar       # require my-foo/models/bar.rb
  collection :bars # require my-foo/models/bars.rb
end

Initialization

Service initialization parameters are enumerated by requires and recognizes. recognizes parameters are optional.

class Foo::Client < Cistern::Service
  requires :hmac_id, :hmac_secret
  recognizes :url
end

# Acceptable
Foo::Client.new(hmac_id: "1", hmac_secret: "2")                            # Foo::Client::Real
Foo::Client.new(hmac_id: "1", hmac_secret: "2", url: "http://example.org") # Foo::Client::Real

# ArgumentError
Foo::Client.new(hmac_id: "1", url: "http://example.org")
Foo::Client.new(hmac_id: "1")

Mocking

Cistern strongly encourages you to generate mock support for service. Mocking can be enabled using mock!.

Foo::Client.mocking?          # falsey
real = Foo::Client.new        # Foo::Client::Real
Foo::Client.mock!
Foo::Client.mocking?          # true
fake = Foo::Client.new        # Foo::Client::Mock
Foo::Client.unmock!
Foo::Client.mocking?          # false
real.is_a?(Foo::Client::Real) # true
fake.is_a?(Foo::Client::Mock) # true

Data

A uniform interface for mock data is mixed into the Mock class by default.

Foo::Client.mock!
client = Foo::Client.new     # Foo::Client::Mock
client.data                  # Cistern::Data::Hash
client.data["bars"] += ["x"] # ["x"]

Mock data is class-level by default

Foo::Client::Mock.data["bars"] # ["x"]

reset! dimisses the data object.

client.data.object_id # 70199868585600
client.reset!
client.data["bars"]   # []
client.data.object_id # 70199868566840

clear removes existing keys and values but keeps the same object.

client.data["bars"] += ["y"] # ["y"]
client.data.object_id        # 70199868378300
client.clear
client.data["bars"]          # []

client.data.object_id        # 70199868566840

• store and []= write
• fetch and [] read

You can make the service bypass Cistern's mock data structures by simply creating a self.data function in your service Mock declaration.

class Foo::Client < Cistern::Service
  class Mock
    def self.data
      @data ||= {}
    end
  end
end

Requests

Mock requests should be defined within the contextual Mock module and interact with the data object directly.

# lib/foo/requests/create_bar.rb
class Foo::Client
  class Mock
    def create_bar(options={})
      id = Foo.random_hex(6)

      bar = {
        "id" => id
      }.merge(options)

      self.data[:bars][id] = bar

      response(
        :body   => {"bar" => bar},
        :status => 201,
        :path => '/bar',
      )
    end
  end # Mock
end # Foo::Client

Storage

Currently supported storage backends are:

• :hash : Cistern::Data::Hash (default)
• :redis : Cistern::Data::Redis

Backends can be switched by using store_in.

# use redis with defaults
Patient::Mock.store_in(:redis)
# use redis with a specific client
Patient::Mock.store_in(:redis, client: Redis::Namespace.new("cistern", redis: Redis.new(host: "10.1.0.1"))
# use a hash
Patient::Mock.store_in(:hash)

Model

• connection represents the associated Foo::Client instance.
• collection represents the related collection (if applicable)

Example

class Foo::Client::Bar < Cistern::Model
  identity :id

  attribute :flavor
  attribute :keypair_id, aliases: "keypair",  squash: "id"
  attribute :private_ips, type: :array

  def destroy
    params  = {
      "id" => self.identity
    }
    self.connection.destroy_bar(params).body["request"]
  end

  def save
    requires :keypair_id

    params = {
      "keypair" => self.keypair_id,
      "bar"     => {
        "flavor" => self.flavor,
      },
    }

    if new_record?
      merge_attributes(connection.create_bar(params).body["bar"])
    else
      requires :identity

      merge_attributes(connection.update_bar(params).body["bar"])
    end
  end
end

Dirty

Dirty attributes are tracked and cleared when merge_attributes is called.

• changed returns a Hash of changed attributes mapped to there initial value and current value
• dirty_attributes returns Hash of changed attributes with there current value. This should be used in the model save function.

bar = Foo::Client::Bar.new(id: 1, flavor: "x") # => <#Foo::Client::Bar>

bar.dirty?           # => false
bar.changed          # => {}
bar.dirty_attributes # => {}

bar.flavor = "y"

bar.dirty?           # => true
bar.changed          # => {flavor: ["x", "y"]}
bar.dirty_attributes # => {flavor: "y"}

bar.save
bar.dirty?           # => false
bar.changed          # => {}
bar.dirty_attributes # => {}

Collection

model tells Cistern which class is contained within the collection. Cistern::Collection inherits from Array and lazy loads where applicable.

class Foo::Client::Bars < Cistern::Collection

  model Foo::Client::Bar

  def all(params = {})
    response = connection.get_bars(params)

    data = response.body

    self.load(data["bars"])     # store bar records in collection
    self.merge_attributes(data) # store any other attributes of the response on the collection
  end

  def discover(provisioned_id, options={})
    params = {
      "provisioned_id" => provisioned_id,
    }
    params.merge!("location" => options[:location]) if options.key?(:location)

    connection.requests.new(connection.discover_bar(params).body["request"])
  end

  def get(id)
    if data = connection.get_bar("id" => id).body["bar"]
      new(data)
    else
      nil
    end
  end
end

Request

module Foo
  class Client
    class Real
      def create_bar(options={})
        request(
          :body     => {"bar" => options},
          :method   => :post,
          :path     => '/bar'
        )
      end
    end # Real

    class Mock
      def create_bar(options={})
        id = Foo.random_hex(6)

        bar = {
          "id" => id
        }.merge(options)

        self.data[:bars][id]= bar

        response(
          :body   => {"bar" => bar},
          :status => 201,
          :path => '/bar',
        )
      end
    end # Mock
  end # Client
end # Foo

Examples

• zendesk2

Releasing

$ gem bump -trv (major|minor|patch)

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request