Add and calculate position to sort group_scores by

app/models/group_score.rb

@@ -9,8 +9,7 @@ class GroupScore < ApplicationRecord
   end
 
   def <=>(other)
-    point_comparison = [-group_points, -difference_in_points, -scored_points] <=> [-other.group_points, -other.difference_in_points, -other.scored_points]
+    point_comparison = [-position, -group_points, -difference_in_points, -scored_points] <=> [-other.position, -other.group_points, -other.difference_in_points, -other.scored_points]
-    p point_comparison, team.name, other.team.name
     if point_comparison.zero?
       comparison_match = group.matches.find do |match|
         match.match_scores.any? { |match_score| match_score.team == team }

app/serializers/group_score_serializer.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 class GroupScoreSerializer < ApplicationSerializer
-  attributes :group_points, :received_points, :scored_points
+  attributes :group_points, :received_points, :scored_points, :position, :difference_in_points
 
   belongs_to :team
 end

app/serializers/group_serializer.rb

@@ -2,11 +2,7 @@
 
 class GroupSerializer < ApplicationSerializer
   attributes :number
-  attributes :group_scores
 
   has_many :matches
-
+  has_many :group_scores
-  def group_scores
-    object.group_scores.sort.map { |group_score| GroupScoreSerializer.new(group_score) }
-  end
 end

app/services/group_stage_service.rb

@@ -85,7 +85,7 @@ class GroupStageService
         end
         changed_group_scores << group_score
       end
-      changed_group_scores
+      recalculate_position_of_group_scores!(changed_group_scores)
     end
 
     # Returns a list of the teams in the group sorted by their group_points, difference_in_points, scored_points
@@ -110,5 +110,42 @@ class GroupStageService
       end
       advancing_teams
     end
+
+    # private
+
+    def recalculate_position_of_group_scores!(group_scores)
+      group_scores.each do |group_score|
+        group_score.position = 0
+      end
+      group_scores = group_scores.sort
+
+      ranks = []
+      rank = 1
+      previous = nil
+      group_scores.each_with_index do |group_score, i|
+        comparison = if i.zero?
+                       1
+                     else
+                       group_score <=> previous
+                     end
+        case comparison
+        when 1
+          ranks.append i
+          rank = i
+        when 0
+          ranks.append rank
+        else
+          raise # should not happen, list is sorted
+        end
+        previous = group_score
+      end
+
+      # assigning position is split into a second loop to not mess up the ranks by adding the position
+      # (which is used for sorting) too early
+      group_scores.each_with_index do |group_score, i|
+        group_score.position = ranks[i] + 1
+      end
+      group_scores
+    end
   end
 end