huginn/app/models/agents/public_transport_agent.rb

require 'date'
require 'cgi'
module Agents
  class PublicTransportAgent < Agent
    cannot_receive_events!
    description <<-MD
      The Public Transport Agent monitors if any bus is expected to arrive at a particular stop in 5 minutes or less.
      You must specify 5 things for it too work correctly. Your state, city, route, stop and destination. All these things
      should be in the language that nextbus understands. For details check out http://www.nextbus.com/predictor/stopSelector.jsp?a=sf-muni and http://www.apihub.com/nextbus/api/nextbus-api/docs/reference.

      Specify the following user settings:
        - stops (array)
        - agency (string)
        - alert_window_in_minutes (integer)

      This Agent generates Events based on NextBus GPS transit predictions.  First, select an agency by visiting http://www.nextbus.com/predictor/agencySelector.jsp and finding your transit system.  Once you find it, copy the part of the URL after `?a=`.  For example, for the San Francisco MUNI system, you would end up on http://www.nextbus.com/predictor/stopSelector.jsp?a=sf-muni and copy "sf-muni".  Put that into this Agent's agency setting.

      Next, find the stop tags that you care about.  To find the tags for the sf-muni system, for the N route, visit this URL:
      http://webservices.nextbus.com/service/publicXMLFeed?command=routeConfig&a=sf-muni&r=N

      The tags are listed as tag="1234".  Copy that number and add the route before it, separated by a pipe (|) symbol.  Once you have one or more tags from that page, add them to this Agent's stop list.  E.g,

          agency: "sf-muni"
          stops: ["N|5221", "N|5215"]

      This Agent will generate predictions by requesting a URL similar to the following:

      http://webservices.nextbus.com/service/publicXMLFeed?command=predictionsForMultiStops&a=sf-muni&stops=N|5221&stops=N|5215

      Finally, set the arrival window that you're interested in.  E.g., 5 minutes.  Events will be created by the agent anytime a new train or bus comes into that time window.

    alert_window_in_minutes: 5

having the agent's default check period be every minute, and creating an Event in #check whenever a new tripTag (supplied by the predictionsForMultiStops API) shows up within alert_window_in_minutes from the stop.  Do not create events for the same tripTag more than once per stop.  I'd do this by keeping a list of [stop tag, tripTag, timestamp] tuples in memory and checking to make sure one doesn't already exist before making a new Event.  This memory should get cleaned up when timestamp is older than an hour (or something) so that it doesn't fill up all of the Agent's memory.

The NextBusAgent doesn't need to receive Events.

It needs to fetch XML from one URL, store a list of timestamps in memory, and make Events.

    MD


    default_schedule "every_2m"

    event_description <<-MD
    Events look like this:
      { "routeTitle":"N-Judah",
        "stopTag":"5215",
        "prediction":
           {"epochTime":"1389622846689",
            "seconds":"3454","minutes":"57","isDeparture":"false",
            "affectedByLayover":"true","dirTag":"N__OB4KJU","vehicle":"1489",
            "block":"9709","tripTag":"5840086"
            }
      }
    MD
    def session
      @session ||= Patron::Session.new
      @session.connect_timeout = 10
      @session.timeout = 60
      @session.headers['Accept-Language'] = 'en-us,en;q=0.5'
      @session.headers['User-Agent'] = "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_4; en-US) AppleWebKit/534.12 (KHTML, like Gecko) Chrome/9.0.584.0 Safari/534.12"
      @session
    end

    def check_url
      stop_query = URI.encode(options["stops"].collect{|a| "&stops=#{a}"}.join)
      "http://webservices.nextbus.com/service/publicXMLFeed?command=predictionsForMultiStops&a=#{options["agency"]}#{stop_query}"
    end

    def stops
      options["stops"].collect{|a| a.split("|").last}
    end
    def check
      page = session.get(check_url)
      page = Nokogiri::XML page.body
      predictions = page.css("//prediction")
      predictions.each do |pr|
        parent = pr.parent.parent
        vals = {routeTitle: parent["routeTitle"], stopTag: parent["stopTag"]}
        if pr["minutes"] && pr["minutes"].to_i < options["alert_window_in_minutes"].to_i
          vals = vals.merge Hash.from_xml(pr.to_xml)
          if not_already_in_memory?(vals)
            create_event(:payload => vals)
            add_to_memory(vals)
          else
          end
        end
      end
    end
    def add_to_memory(vals)
      self.memory["existing_routes"] ||= []
      self.memory["existing_routes"] << {stopTag: vals["stopTag"], tripTag: vals["prediction"]["tripTag"], epochTime: vals["prediction"]["epochTime"], currentTime: Time.now}
    end
    def not_already_in_memory?(vals)
      m = self.memory["existing_routes"]
      m.select{|h| h[:stopTag] == vals["stopTag"] &&
                h[:tripTag] == vals["prediction"]["tripTag"] &&
                h[:epochTime] == vals["prediction"]["epochTime"]
              }.count == 0
    end
    def default_options
      {
        agency: "sf-muni",
        stops: ["N|5221", "N|5215"],
        alert_window_in_minutes: 5
      }
    end

    def validate_options
      errors.add(:base, 'agency is required') unless options['agency'].present?
      errors.add(:base, 'alert_window_in_minutes is required') unless options['alert_window_in_minutes'].present?
      errors.add(:base, 'stops are required') unless options['stops'].present?
    end
    def working?
      event_created_within?(2) && !recent_error_logs?
    end
  end
end