log_request_and_response.rb

class LogRequestAndResponse
  def initialize(app); @app = app; end
  def call(env)
    req = Rack::Request.new(env)

    headers = Hash[*env.select {|k,v| k.start_with? 'HTTP_'}
		  .collect {|k,v| [k.sub(/^HTTP_/, ''), v]}
		  .collect {|k,v| [k.split('_').collect(&:capitalize).join('-'), v]}
		  .sort
		  .flatten]

    puts "<-- #{req.request_method} #{req.url} #{req.params.inspect} #{headers.inspect}"
    status, headers, body = @app.call(env)

    puts "--> #{status} #{(JSON.load(body.first) rescue '- stripped -').inspect} #{headers.inspect}"
    [status, headers, body]
  end
end