Example of allowing a faraday connection to be configured through middleware blocks.

silo_client.rb

module Silo
  module Client
    extend self

    def configuration
      @configuration ||= Configuration.new
    end

    def configure
      yield configuration
    end

    def connection
      @connection ||= begin
        unless configuration.json_engine
          raise MissingConfigurationError.new("configuration.json_engine has not been set")
        end
        MultiJson.engine = configuration.json_engine

        Faraday.new("http://#{configuration.host}:#{configuration.port}") do |builder|
          builder.use Silo::Client::Middleware::APIVersioning
          builder.request  :json
          builder.use Faraday::Response::Mashify.tap { |m| m.mash_class = FrozenMash }
          builder.use Silo::Client::Middleware::ParseJSON
          builder.use Silo::Client::Middleware::RaiseError
          builder.adapter configuration.http_lib || Faraday.default_adapter

          configuration.middleware_blocks.each do |block|
            block.call(builder)
          end
        end.tap do |conn|
          conn.basic_auth(configuration.username, configuration.password)
        end
      end
    end

    class Configuration
      attr_accessor :host,
                    :port,
                    :username,
                    :password,
                    :http_lib,
                    :feed_delay,
                    :json_engine,
                    :subscription_namespace,
                    :api_version,
                    :hmac_access_id,
                    :hmac_secret_key

      def initialize
        self.api_version = 1
      end

      def middleware(&block)
        middleware_blocks << block
      end

      def middleware_blocks
        @middleware_blocks ||= []
      end
    end
  end
end