Nancy is a Sinatra like micro framework for study base on thoughtbot blog: https://robots.thoughtbot.com/lets-build-a-sinatra

nancy.rb

require 'rubygems'
require 'bundler/setup'

require 'rack'
require 'pry'

module Nancy
  METHODS = %w(get post put patch delete head)

  class Base
    def initialize
      @routes = {}
    end

    attr_reader :routes, :request
    
    METHODS.each do |method|
      define_method(method) do |path, &handler|
        route(method.upcase, path, &handler)
      end
    end

    def params
      request.params
    end

    def call(env)
      @request = Rack::Request.new env
      verb = @request.request_method
      requested_path = @request.path_info

      if (handlers = @routes[verb]) && (handler = handlers[requested_path])
        result = instance_eval &handler 

        if result.class == String
          [200, {}, [result]]
        else
          result
        end
      else
        [404, {}, ["Oops! No route for #{verb} #{requested_path}"]]
      end
    end

    private
      def route(verb, path, &handler)
        @routes[verb] ||= {}
        @routes[verb][path] = handler
      end
  end

  Application = Base.new

  module Delegator
    def self.delegate(*methods, to:)
      methods.each do |method|
        define_method(method) do |*args, &block|
          to.send(method, *args, &block)
        end

        private method
      end
    end

    delegate *METHODS, to: Application
  end
end

# # nancy = Nancy::Application
#
# nancy.get '/' do
#   [200, {}, ["Your params are #{params.inspect}"]]
# end
#
# nancy.post '/' do
#   [200, {}, request.body]
# end
#
# nancy.get '/hello' do
#   'hello from nancy'
# end

include Nancy::Delegator

post '/' do
  request.body.read
end

Rack::Handler::WEBrick.run Nancy::Application, Port: 9292