require 'base64'
require 'cgi'
require 'hmac-sha1'

module App42
  module Client
    class RestUtil

      #
      # Finds the current time
      #
      # @return time format
      #
      #
      def get_timestamp_utc
        timestamp = Time.now.utc.strftime("%Y-%m-%dT%H:%M:%S.%LZ")
        return timestamp.freeze
      end

      #
      # It signs the request that has to be sent in the Hmac format.
      #
      # @param secretKey
      # @param params
      #
      # @rescue InvalidKeyException
      #
      def sign secret_key, params
        sorted_params =  sort_convert_table(params)
        signature = compute_hmac(secret_key, sorted_params)
        signature
      end

      #
      # This method sorts all the values that are stored in the table.
      #
      # @param table
      # @return sorted string
      #
      #
      def sort_convert_table(table)
        sorted_params = ""
        table.sort {|a,b| a[0] <=> b[0]}.each{ |key, val|
          sorted_params << key
          sorted_params << val
        }
        sorted_params
      end

      #
      # Encoding and decoding of the queries are done using the Hmac Algorithm.
      #
      # @param baseString
      # @param key
      #
      # @rescue NoSuchAlgorithmException
      #
      def compute_hmac(secret_key, sorted_params)
        signature =  Base64.encode64(HMAC::SHA1::digest(secret_key, sorted_params)).strip
        computed_hmac = CGI.escape(signature)
        computed_hmac
      end

    end
  end
end