Rack middleware for returning pretty JSON when `pretty` parameter is present and it's not `"false"`.

pretty_json.rb

module Rack

  # Prettify JSON responses on demand.
  #
  #
  #
  # Builder Usage:
  #   use Rack::PrettyJSON
  #
  class PrettyJSON
    include Rack::Utils

    def initialize(app)
      @app = app
    end

    def call(env)
      status, headers, response = @app.call(env)

      headers = HeaderHash.new(headers)
      request = Rack::Request.new(env)

      if is_json?(headers) && should_prettify?(request)
        response = prettify(response)

        # Set new Content-Length, if it was set before we mutated the response body
        if headers["Content-Length"]
          length = response.to_ary.inject(0) { |len, part| len + bytesize(part) }
          headers["Content-Length"] = length.to_s
        end
      end

      [status, headers, response]
    end

    private

    def is_json?(headers)
      headers.key?("Content-Type") && headers["Content-Type"].include?("application/json")
    end

    def should_prettify?(request)
      request.params.has_key?("pretty") && !(request.params["pretty"] == "false")
    end

    def prettify(response)
      body = response.inject("") { |body, part| body << part.to_s }
      [JSON.pretty_generate(JSON.parse(body))]
    end
  end
end