module WopiUtil
  require 'open-uri'

  # Used for timestamp
  UNIX_EPOCH_IN_CLR_TICKS = 621355968000000000
  CLR_TICKS_PER_SECOND = 10000000

  DISCOVERY_TTL = 60*60*24
  DISCOVERY_TTL.freeze

  # For more explanation see this:
  # http://stackoverflow.com/questions/11888053/
  # convert-net-datetime-ticks-property-to-date-in-objective-c
  def convert_to_unix_timestamp(timestamp)
    Time.at((timestamp-UNIX_EPOCH_IN_CLR_TICKS)/CLR_TICKS_PER_SECOND)
  end

  def get_action(extension, activity)
    get_discovery
    action = WopiAction.find_action(extension, activity)
  end

  def get_discovery
    discovery = WopiDiscovery.first
    return discovery if discovery && discovery.expires >= Time.now.to_i
    initialize_discovery(discovery)
  end

  private

  # Currently only saves Excel, Word and PowerPoint view and edit actions
  def initialize_discovery(discovery)
    begin
      Rails.logger.warn "Initializing discovery"
      discovery.destroy if discovery

      @doc = Nokogiri::XML(open(ENV["WOPI_DISCOVERY_URL"]))

      discovery = WopiDiscovery.new
      discovery.expires = Time.now.to_i + DISCOVERY_TTL
      key = @doc.xpath("//proof-key")
      discovery.proof_key_mod = key.xpath("@modulus").first.value
      discovery.proof_key_exp = key.xpath("@exponent").first.value
      discovery.proof_key_old_mod = key.xpath("@oldmodulus").first.value
      discovery.proof_key_old_exp = key.xpath("@oldexponent").first.value
      discovery.save!

      @doc.xpath("//app").each do |app|
        app_name = app.xpath("@name").first.value
        if ["Excel","Word","PowerPoint","WopiTest"].include?(app_name)
          wopi_app = WopiApp.new
          wopi_app.name = app.xpath("@name").first.value
          wopi_app.icon = app.xpath("@favIconUrl").first.value
          wopi_app.wopi_discovery_id=discovery.id
          wopi_app.save!
          app.xpath("action").each do |action|
            name = action.xpath("@name").first.value
            if ["view","edit","wopitest"].include?(name)
              wopi_action = WopiAction.new
              wopi_action.action = name
              wopi_action.extension = action.xpath("@ext").first.value
              wopi_action.urlsrc = action.xpath("@urlsrc").first.value
              wopi_action.wopi_app_id = wopi_app.id
              wopi_action.save!
            end
          end
        end
      end
      discovery
    rescue
      Rails.logger.warn "Initialization failed"
      discovery = WopiDiscovery.first
      discovery.destroy if discovery
    end

  end

end