app/controllers/affinities_controller.rb

@@ -0,0 +1,36 @@
+# Copyright (C) 2024 Manuel Bustillo
+
+# frozen_string_literal: true
+
+class AffinitiesController < ApplicationController
+  before_action :set_group
+
+  def index
+    overridden_affinities = @group.affinities
+      .each_with_object({}) { |affinity, acc| acc[affinity.another_group(@group).id] = affinity.discomfort }
+    Group.pluck(:id).index_with { |group_id| overridden_affinities[group_id] || GroupAffinity::NEUTRAL }
+      .then { |affinities| render json: affinities }
+  end
+
+  def bulk_update
+    params.expect(affinities: [[:group_id, :discomfort]]).map(&:to_h).map do |affinity|
+      {
+        group_a_id: @group.id,
+        group_b_id: affinity[:group_id],
+        discomfort: affinity[:discomfort]
+      }
+    end.then { |affinities| GroupAffinity.upsert_all(affinities) }
+    render json: {}, status: :ok
+
+  rescue ActiveRecord::InvalidForeignKey
+    render json: { error: 'At least one of the group IDs provided does not exist.' }, status: :bad_request
+  rescue ActiveRecord::StatementInvalid
+    render json: { error: 'Invalid group ID or discomfort provided.' }
+  end
+
+  private
+
+  def set_group
+    @group = Group.find(params[:group_id])
+  end
+end

app/models/group.rb

@@ -54,6 +54,10 @@ class Group < ApplicationRecord
     end
   end
   
+  def affinities
+    GroupAffinity.where(group_a_id: id).or(GroupAffinity.where(group_b_id: id))
+  end
+
   private
 
   def set_color

app/models/group_affinity.rb

@@ -0,0 +1,38 @@
+# == Schema Information
+#
+# Table name: group_affinities
+#
+#  id         :bigint           not null, primary key
+#  discomfort :float            not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#  group_a_id :uuid             not null
+#  group_b_id :uuid             not null
+#
+# Indexes
+#
+#  index_group_affinities_on_group_a_id  (group_a_id)
+#  index_group_affinities_on_group_b_id  (group_b_id)
+#  uindex_group_pair                     (LEAST(group_a_id, group_b_id), GREATEST(group_a_id, group_b_id)) UNIQUE
+#
+# Foreign Keys
+#
+#  fk_rails_...  (group_a_id => groups.id)
+#  fk_rails_...  (group_b_id => groups.id)
+#
+class GroupAffinity < ApplicationRecord
+  NEUTRAL = 1
+  MIN_DISCOMFORT = 0
+  MAX_DISCOMFORT = 2
+
+  belongs_to :group_a, class_name: 'Group'
+  belongs_to :group_b, class_name: 'Group'
+
+  validates :discomfort, numericality: { greater_than_or_equal_to: MIN_DISCOMFORT, less_than_or_equal_to: MAX_DISCOMFORT }
+
+  def another_group(group)
+    return nil if group != group_a && group != group_b
+
+    group == group_a ? group_b : group_a
+  end
+end

app/services/tables/discomfort_calculator.rb

@@ -2,6 +2,15 @@
 
 module Tables
   class DiscomfortCalculator
+    class << self
+      def cohesion_discomfort(id_a:, id_b:)
+        distance = AffinityGroupsHierarchy.instance.distance(id_a, id_b)
+
+        return 1 if distance.nil?
+        Rational(distance, distance + 1)
+      end
+    end
+
     private attr_reader :table
     def initialize(table:)
       @table = table
@@ -45,12 +54,7 @@ module Tables
     #
     def cohesion_discomfort
       table.map(&:group_id).tally.to_a.combination(2).sum do |(a, count_a), (b, count_b)|
-        distance = AffinityGroupsHierarchy.instance.distance(a, b)
-
-        next count_a * count_b if distance.nil?
-        next 0 if distance.zero?
-
-        count_a * count_b * Rational(distance, distance + 1)
+        count_a * count_b * self.class.cohesion_discomfort(id_a: a, id_b: b)
       end
     end
   end

config/routes.rb

@@ -23,7 +23,12 @@ Rails.application.routes.draw do
       get '/users/confirmation', to: 'users/confirmations#show', as: :confirmation
     end
 
-    resources :groups, only: %i[index create update destroy]
+    resources :groups, only: %i[index create update destroy] do
+      resources :affinities, only: %i[index] do
+        put :bulk_update, on: :collection
+      end
+    end
+
     resources :guests, only: %i[index create update destroy] do
       post :bulk_update, on: :collection
     end

db/migrate/20241216231415_create_group_affinities.rb

@@ -0,0 +1,27 @@
+class CreateGroupAffinities < ActiveRecord::Migration[8.0]
+  disable_ddl_transaction!
+
+  def change
+    create_table :group_affinities, if_not_exists: true do |t|
+      t.references :group_a, type: :uuid, null: false, foreign_key: { to_table: :groups }
+      t.references :group_b, type: :uuid, null: false, foreign_key: { to_table: :groups }
+      t.float :discomfort, null: false
+      t.timestamps
+    end
+
+    add_check_constraint :group_affinities, 'group_a_id != group_b_id', name: :check_distinct_groups, if_not_exists: true
+    add_check_constraint :group_affinities, 'discomfort >= 0 AND discomfort <= 2', if_not_exists: true
+
+    reversible do |dir|
+      dir.up do
+        execute <<~SQL
+          CREATE UNIQUE INDEX CONCURRENTLY uindex_group_pair ON group_affinities (least(group_a_id, group_b_id), greatest(group_a_id, group_b_id));
+        SQL
+      end
+
+      dir.down do
+        remove_index :group_affinities, name: :uindex_group_pair, if_exists: true
+      end
+    end
+  end
+end

db/schema.rb

@@ -1,5 +1,3 @@
-# Copyright (C) 2024 Manuel Bustillo
-
 # This file is auto-generated from the current state of the database. Instead
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.
@@ -12,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2024_12_08_102932) do
+ActiveRecord::Schema[8.0].define(version: 2024_12_16_231415) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_catalog.plpgsql"
 
@@ -30,6 +28,19 @@ ActiveRecord::Schema[8.0].define(version: 2024_12_08_102932) do
     t.index ["wedding_id"], name: "index_expenses_on_wedding_id"
   end
 
+  create_table "group_affinities", force: :cascade do |t|
+    t.uuid "group_a_id", null: false
+    t.uuid "group_b_id", null: false
+    t.float "discomfort", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index "LEAST(group_a_id, group_b_id), GREATEST(group_a_id, group_b_id)", name: "uindex_group_pair", unique: true
+    t.index ["group_a_id"], name: "index_group_affinities_on_group_a_id"
+    t.index ["group_b_id"], name: "index_group_affinities_on_group_b_id"
+    t.check_constraint "discomfort >= 0::double precision AND discomfort <= 2::double precision"
+    t.check_constraint "group_a_id <> group_b_id", name: "check_distinct_groups"
+  end
+
   create_table "groups", id: :uuid, default: -> { "gen_random_uuid()" }, force: :cascade do |t|
     t.string "name", null: false
     t.string "icon"
@@ -228,6 +239,8 @@ ActiveRecord::Schema[8.0].define(version: 2024_12_08_102932) do
   end
 
   add_foreign_key "expenses", "weddings"
+  add_foreign_key "group_affinities", "groups", column: "group_a_id"
+  add_foreign_key "group_affinities", "groups", column: "group_b_id"
   add_foreign_key "groups", "groups", column: "parent_id"
   add_foreign_key "groups", "weddings"
   add_foreign_key "guests", "groups"

docker-compose.yml

@@ -11,6 +11,13 @@ services:
     environment: 
       DATABASE_URL: postgres://postgres:postgres@db:5432/postgres
       RAILS_ENV: development
+    tty: true
+    stdin_open: true
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:3000/up"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
     volumes:
       - .:/rails
   workers:
@@ -32,6 +39,11 @@ services:
       dockerfile: Dockerfile.dev
     ports:
       - 3000
+    healthcheck:
+      test: wget -qO - http://localhost:3000/api/health || exit 1
+      interval: 10s
+      timeout: 5s
+      retries: 5
     depends_on:
       - backend
     volumes:
@@ -50,8 +62,10 @@ services:
     volumes:
       - ./nginx.conf:/etc/nginx/conf.d/default.conf:ro
     depends_on:
-      - frontend
-      - backend    
+      frontend:
+        condition: service_healthy
+      backend:
+        condition: service_healthy
   db:
     image: postgres:17
     ports:

spec/factories/group_affinities.rb

@@ -0,0 +1,7 @@
+FactoryBot.define do
+  factory :group_affinity do
+    association :group_a, factory: :group
+    association :group_b, factory: :group
+    discomfort { GroupAffinity::NEUTRAL }
+  end
+end

spec/models/group_affinity_spec.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe GroupAffinity, type: :model do
+  let(:wedding) { create(:wedding) }
+  let(:group_a) { create(:group, wedding:) }
+  let(:group_b) { create(:group, wedding:) }
+  let(:group_c) { create(:group, wedding:) }
+
+  subject { build(:group_affinity, group_a:, group_b: ) }
+
+  describe 'validations' do
+    it { should validate_numericality_of(:discomfort).is_greater_than_or_equal_to(0).is_less_than_or_equal_to(2) }
+  end
+
+  describe '.create' do
+    before do
+      create(:group_affinity, group_a: group_a, group_b: group_b)
+    end
+
+    it 'disallows the creation of a group affinity with the same group on both sides' do
+      expect do
+        create(:group_affinity, group_a: group_c, group_b: group_c)
+      end.to raise_error(ActiveRecord::StatementInvalid)
+    end
+
+    it 'disallows the creation of a group affinity that already exists' do
+      expect do
+        create(:group_affinity, group_a: group_a, group_b: group_b)
+      end.to raise_error(ActiveRecord::StatementInvalid)
+    end
+
+    it 'disallows the creation of a group affinity with the same groups in reverse order' do
+      expect do
+        create(:group_affinity, group_a: group_b, group_b: group_a)
+      end.to raise_error(ActiveRecord::StatementInvalid)
+    end
+  end
+end

spec/requests/affinities_spec.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+require 'swagger_helper'
+
+RSpec.describe 'affinities', type: :request do
+  path '/{slug}/groups/{group_id}/affinities' do
+    parameter Swagger::Schema::SLUG
+    parameter name: 'group_id', in: :path, type: :string, format: :uuid, description: 'group_id'
+
+    get('list affinities') do
+      tags 'Affinities'
+      produces 'application/json'
+
+      response(200, 'successful') do
+        schema type: :object, additionalProperties: { type: :integer, minimum: 0, maximum: 2 }
+        xit
+      end
+    end
+  end
+
+  path '/{slug}/groups/{group_id}/affinities/bulk_update' do
+    parameter Swagger::Schema::SLUG
+    parameter name: 'group_id', in: :path, type: :string, format: :uuid, description: 'group_id'
+
+    put('bulk update affinities') do
+      tags 'Affinities'
+      produces 'application/json'
+      consumes 'application/json'
+      parameter name: :body, in: :body, schema: {
+        type: :object,
+        required: [:affinities],
+        properties: {
+          affinities: {
+            type: :array,
+            items: {
+              type: :object,
+              required: %i[group_id discomfort],
+              properties: {
+                group_id: { type: :string, format: :uuid, description: 'ID of the associated group' },
+                discomfort: { type: :integer, minimum: 0, maximum: 2 }
+              }
+            }
+          }
+        }
+      }
+
+      response_empty_200
+    end
+  end
+end