hpi-swt2/sport-portal

# == Schema Information
#
# Table name: participants
#
#  id         :integer          not null, primary key
#  event_id   :integer
#  team_id    :integer
#  rating     :float
#  created_at :datetime         not null
#  updated_at :datetime         not null
#

class Participant < ApplicationRecord
  belongs_to :team
  belongs_to :event

  def update_elo_for(match_result, opponent)
    opponent_rating = opponent.rating
    k_factor = event.maximum_elo_change
    expectation = 1.0 / (1.0 + (10.0**((opponent_rating - rating) / 400.0)))
    update(rating: rating + k_factor * (match_result - expectation))
    opponent.update(rating: opponent_rating + k_factor * (expectation - match_result))
  end
end