module Tekeya
  module Feed
    module Activity
      module Resque
        extend ActiveSupport::Concern

        included do
          MAXTIMESTAMP = 10.days.ago.to_i unless defined?(MAXTIMESTAMP)
        end

        module ClassMethods
          private
          # Writes the activity reference to the feed with the supplied key
          #
          # @param [String]  feed_key the key of the feed where the activity will be referenced
          # @param [Integer] score the score of the activity (timestamp) used to order the feed
          # @param [String]  activity_key a string containing the key to reference the activity
          def write_to_feed(feed_key, score, activity_key)
            # add the activity to the owner's profile feed
            ::Tekeya.redis.zadd(feed_key, score, activity_key)
            # increment the activity counter to keep track of its presence in feeds
            activity_counter_key = "#{activity_key}:counter"
            ::Tekeya.redis.incr(activity_counter_key)
          end

          # Trims the feed according to the MAXTIMESTAMP set and returns the removed keys (for garbage collection)
          #
          # @param [String] feed_key a string containing the key of the feed to be trimed
          def trim_feed(feed_key)
            removed_keys = ::Tekeya.redis.zrevrangebyscore(feed_key, '-inf', MAXTIMESTAMP)
            ::Tekeya.redis.zremrangebyscore(feed_key, '-inf', MAXTIMESTAMP)

            return removed_keys
          end

          # Checks if the given keys are referenced in any feed otherwise removes the activity
          #
          # @param [Array] keys an array of activity keys to be removed
          def collect_garbage(keys)
            keys.each do |key|
              activity_counter_key = "#{key}:counter"
              # Check if the key is referenced anywhere
              if ::Tekeya.redis.get(activity_counter_key).to_i <= 0
                # Delete the activity and the counter
                ::Tekeya.redis.multi do
                  ::Tekeya.redis.del(key)
                  ::Tekeya.redis.del(activity_counter_key)
                end
              end
            end
          end
        end
      end
    end
  end
end