MessageExpiration

message_expiration.rb

# Stores and retrieves messages to be expired on a given date
#
# Messages can be added, removed, and expired.  The actual removal
# of the messages from the user's account is not handled here.
#
class MessageExpiration
  attr_reader :eea_id

  def inititialize(eea_id)
    @eea_id = eea_id
  end

  # Add messages to be expired on a specific date
  #
  def record_messages_for_expiry(folder, message_ids, expiration_date)
    Array(message_ids).each do |id|
      $redis.zadd eea_id, days_since_epoch(expiration_date), member_string(folder, id)
    end
  end

  # Remove messages before their expiration date, preventing
  # them fromm being removed.  Intended to be used in cases where
  # we decide not to expire a message (ex: if a user opens a message)
  #
  def prevent_expiry(folder, message_ids)
    Array(message_ids).each do |id|
      $redis.zrem eea_id, member_string(folder, id)
    end
  end

  # Pops messages set to expire by the given date and returns them
  # as a hash keyed by folder name.
  #
  # ex: "OIB/Finance" => [231,5343,343,234,4], "OIB/News" => [234,153]
  #
  def expire_messages(until_date=DateTime.now)
    messages = messages_to_expire(eea_id, until_date)
    $redis.zremrangebyscore eea_id, 0, days_since_epoch(until_date)
    messages
  end


  # Private Methods
  
  def messages_to_expire(until_date)
    messages = {}
    $redis.zrangebyscore(eea_id, 0, days_since_epoch(until_date)).each do |message|
      folder, message_id = message_parts(message)
      messages[folder] ||= []
      messages[folder] << message_id
    end
    messages
  end

  def days_since_epoch(date)
    (date - epoch).to_i
  end

  def epoch
    Date.new(1970,1,1)
  end

  def message_parts(message)
    message.split("::")
  end

  def member_string(folder, message_id)
    "#{folder}::#{message_id}"
  end
end