# Remembers the campaign parameters a player arrived with, so the printed QR
# codes can be told apart in the admin dashboard.
#
# The QR codes point at the bare domain, which redirects to /:locale and drops
# the query string -- and the player row is not created until the language page
# posts to game#start. The tags are therefore parked in the session on the way
# in and read back out when the player is created.
#
# Last touch wins: a second scan is a second visit, and the player row that
# follows it belongs to the code that was actually scanned.
module UtmTracking
  extend ActiveSupport::Concern

  SESSION_KEY = "utm".freeze

  included do
    before_action :capture_utm
  end


private


  def capture_utm
    tags = Player::UTM_KEYS.index_with { |key| clean_utm(params[key]) }.compact
    return if tags.empty?

    # String keys: the session round-trips through the cookie, which has no
    # symbols, so `utm_attributes` would stop matching after the redirect.
    session[SESSION_KEY] = tags.transform_keys(&:to_s)
  end


  # Query parameters are typed by whoever holds the link, so they are trimmed
  # to something a column and a dashboard row can live with.
  def clean_utm(value)
    value.to_s.strip.first(100).presence
  end


  def utm_attributes
    (session[SESSION_KEY] || {}).slice(*Player::UTM_KEYS.map(&:to_s))
  end
end