connection.rb

module Mettlr
  class Connection
    def self.connection
      @connection = Faraday.new('http://api.mettl.com/v1') do |c|
        c.options.params_encoder = Faraday::FlatParamsEncoder
        c.request :url_encoded
        # c.request :json
        c.response :mashify
        c.response :json, content_type: /\bjson$/
        c.response :logger
        c.use :instrumentation
        c.adapter :net_http
      end
    end
    def self.get(path)
      connection.get do |req|
        req.path = path
        req.params['ak'] = Mettlr::METTL_PUBLIC_KEY
        req.params['ts'] = Time.now.to_i.to_s
        req.params = Hash[req.params.sort_by {|k,v| k.downcase}]
        req.params['asgn'] = Mettlr::Signature.new(req).signature
      end
    end
    def self.post(path, options)
      connection.post do |req|
        req.path = path
        req.params['ak'] = Mettlr::METTL_PUBLIC_KEY
        req.params['ts'] = Time.now.to_i.to_s
        options.each do |k,v|
          if v.is_a?(Hash)
            req.params[k] = v.to_json
          else
            req.params[k] = v
          end
        end
        req.params = Hash[req.params.sort_by {|k,v| k.downcase}]
        req.params['asgn'] = Mettlr::Signature.new(req).signature
      end
    end
  end
end

sig_gen.rb

module Mettlr
  class Signature
    def initialize(request)
      @request = request
    end

    def concat_string
      @request.method.to_s.upcase +
        "http://api.mettl.com" + 
        @request.path + 
        param_values
    end
    def param_values
      "\n" + @request.params.values.join("\n")
    end
    def signature
      hmac = OpenSSL::HMAC.digest('sha1', Mettlr::METTL_PRIVATE_KEY, concat_string)
      Faraday::Utils.escape(Base64.encode64(hmac).chomp)
    end
  end
end