Wechat Signature Validator

wechat.rb

module Wechat
  class SignatureValidator
    attr_accessor :token, :params

    def initialize(token, params)
      @token = token 
      @params = params
    end 

    def calculate
      require 'openssl' unless defined?(OpenSSL)
      text = %w(timestamp nonce).map {|name| params[name].to_s}.push(token).sort.join
      Digest::SHA1.hexdigest text         
    end 

    def valid?
      calculate == params['signature']
    end 
  end 
end