gistfile1.rb

require 'faraday'
require 'debugger'
# require File.join(File.dirname(__FILE__), 'lib/active_resource')

module ActiveResource
  module Request
    class PerRequestToken < Faraday::Middleware

      def initialize(app = nil, options = {})
        @per_options = options
        super(app)
      end

      def call(env)
        if @per_options[:request_auth_token]
          env[:request_headers].merge!('X-AUTH-TOKEN' => @per_options[:request_auth_token])
        end
        @app.call(env)
      end
    end
  end
end

class Scope
  attr_reader :stack

  def initialize
    @stack ||= {}
  end
  
  def add(middleware, args)
    @stack[middleware] = args
  end

end


# base connection method
def connection
  Faraday.new("http://localhost") do |builder|
    yield builder if block_given?
  
    builder.adapter :test do |stub|
      stub.get('/something') {[ 200, {}, 'yay' ]}
    end
  end
end

@scope = Scope.new()
@scope.add(ActiveResource::Request::PerRequestToken, :request_auth_token => 'sekret')
x = connection { |builder|
  @scope.stack.each do |scope, params|
    builder.use scope, params
  end
}.get('/something')

puts x.env[:request_headers] # {"X-AUTH-TOKEN"=>"sekret"}


@scope = Scope.new
y = connection { |builder|
  @scope.stack.each do |scope, params|
    builder.use scope, params
  end
}.get('/something')
puts y.env[:request_headers] # {}