david
1268889a78
- Implement EloCalculator service for 2v2 Euchre matches - Create background job processing with GoodJob - Add single match entry form - Add CSV upload for batch match entry - Create player rankings view - Add database schema for matches and elo snapshots
81 lines
2.9 KiB
Ruby
81 lines
2.9 KiB
Ruby
# frozen_string_literal: true
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module EuchreCamp
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module Services
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class EloCalculator
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# Standard Elo K-factor
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K_FACTOR = 32
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# Calculate Elo ratings for a 2v2 Euchre match
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#
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# @param player_ratings [Hash] player_id => current_rating
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# @param team_1_players [Array<Integer>] player IDs for team 1
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# @param team_2_players [Array<Integer>] player IDs for team 2
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# @param team_1_score [Integer] score for team 1
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# @param team_2_score [Integer] score for team 2
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# @return [Hash] player_id => { rating_before:, rating_after:, rating_change: }
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def self.calculate(player_ratings:, team_1_players:, team_2_players:, team_1_score:, team_2_score:)
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# Validate inputs
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raise ArgumentError, "Team 1 must have exactly 2 players" unless team_1_players.length == 2
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raise ArgumentError, "Team 2 must have exactly 2 players" unless team_2_players.length == 2
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# Determine winner (first to 10 points)
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team_1_wins = team_1_score >= 10
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team_2_wins = team_2_score >= 10
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unless team_1_wins || team_2_wins
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raise ArgumentError, "One team must reach 10 points to win"
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end
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if team_1_wins && team_2_wins
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raise ArgumentError, "Only one team can win (both reached 10 points)"
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end
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winner = team_1_wins ? :team_1 : :team_2
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# Calculate average ratings for each team
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team_1_avg = team_1_players.map { |id| player_ratings[id] }.sum / 2.0
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team_2_avg = team_2_players.map { |id| player_ratings[id] }.sum / 2.0
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# Calculate expected scores using Elo formula
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# E = 1 / (1 + 10^((R_opp - R_team) / 400))
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expected_team_1 = 1.0 / (1.0 + 10.0**((team_2_avg - team_1_avg) / 400.0))
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expected_team_2 = 1.0 / (1.0 + 10.0**((team_1_avg - team_2_avg) / 400.0))
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# Actual scores (1 for win, 0 for loss)
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actual_team_1 = team_1_wins ? 1.0 : 0.0
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actual_team_2 = team_2_wins ? 1.0 : 0.0
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# Calculate rating changes for each player
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results = {}
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# Team 1 players
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team_1_players.each do |player_id|
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old_rating = player_ratings[player_id]
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rating_change = K_FACTOR * (actual_team_1 - expected_team_1)
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new_rating = (old_rating + rating_change).round
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results[player_id] = {
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rating_before: old_rating,
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rating_after: new_rating,
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rating_change: rating_change.round
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}
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end
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# Team 2 players
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team_2_players.each do |player_id|
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old_rating = player_ratings[player_id]
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rating_change = K_FACTOR * (actual_team_2 - expected_team_2)
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new_rating = (old_rating + rating_change).round
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results[player_id] = {
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rating_before: old_rating,
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rating_after: new_rating,
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rating_change: rating_change.round
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}
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end
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results
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end
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end
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end
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end
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