Redo simulations lifecycle (#222)

## Why

The current way of creating and deleting simulations doesn't scale for big instances. We cannot generate 50 simulations every time a guest confirms attendance, and we should not delete existing valuable simulations. For example, if a guest confirms attendance and declines right after, previously generated simulations should still be valid.

## What

In this PR we are introducing a series of changes that make simulations management easier:

1. We're removing the automatic creation of simulations.
2. Simulations are not removed anymore, neither manually nor automatically.
3. A new endpoint has been defined to create simulations on demand.
4. A digest property has been defined to determine whether a simulation is still valid (meaning there have not been any change in the list of guests involved).

Reviewed-on: #222
Co-authored-by: Manuel Bustillo <bustikiller@bustikiller.com>
Co-committed-by: Manuel Bustillo <bustikiller@bustikiller.com>

app/controllers/tables_arrangements_controller.rb

@@ -4,7 +4,15 @@
 
 class TablesArrangementsController < ApplicationController
   def index
-    render json: TablesArrangement.order(discomfort: :asc).limit(3).as_json(only: %i[id name discomfort])
+    current_digest = Tables::Distribution.digest(current_tenant)
+
+    render json: TablesArrangement
+      .order(valid: :desc)
+      .order(discomfort: :asc)
+      .select(:id, :name, :discomfort)
+      .select("digest = '#{current_digest}'::uuid as valid")
+      .limit(20)
+      .as_json(only: %i[id name discomfort valid])
   end
 
   def show
@@ -16,6 +24,12 @@ class TablesArrangementsController < ApplicationController
          .then { |result| render json: { id: params[:id], tables: result } }
   end
 
+  def create
+    TableSimulatorJob.perform_later(current_tenant.id)
+
+    render json: {}, status: :created
+  end
+
   private
 
   def format(number:, guests:)

app/models/guest.rb

@@ -41,16 +41,5 @@ class Guest < ApplicationRecord
 
   scope :potential, -> { where.not(status: %i[declined considered]) }
 
-  after_destroy :recalculate_simulations
-  after_save :recalculate_simulations, if: :saved_change_to_status?
-
   has_many :seats, dependent: :delete_all
-
-  private
-
-  def recalculate_simulations
-    TablesArrangement.delete_all
-
-    ActiveJob.perform_all_later(50.times.map { TableSimulatorJob.new(wedding_id) })
-  end
 end

app/models/tables_arrangement.rb

@@ -7,6 +7,7 @@
 # Table name: tables_arrangements
 #
 #  id         :uuid             not null, primary key
+#  digest     :uuid             not null
 #  discomfort :integer
 #  name       :string           not null
 #  created_at :datetime         not null

app/models/wedding.rb

@@ -19,4 +19,6 @@ class Wedding < ApplicationRecord
   SLUG_REGEX = /[a-z\d-]+/
 
   validates :slug, presence: true, uniqueness: true, format: { with: /\A#{SLUG_REGEX}\z/ }
+
+  has_many :guests, dependent: :delete_all
 end

app/services/tables/distribution.rb

@@ -6,7 +6,13 @@ require_relative '../../extensions/tree_node_extension'
 
 module Tables
   class Distribution
-    attr_accessor :tables, :min_per_table, :max_per_table
+    class << self
+      def digest(wedding)
+        Digest::UUID.uuid_v5(wedding.id, wedding.guests.potential.order(:id).pluck(:id).join)
+      end
+    end
+
+    attr_accessor :tables, :min_per_table, :max_per_table, :hierarchy
 
     def initialize(min_per_table:, max_per_table:)
       @min_per_table = min_per_table
@@ -54,7 +60,10 @@ module Tables
 
         Seat.insert_all!(records_to_store)
 
-        arrangement.update!(discomfort:)
+        arrangement.update!(
+          discomfort:,
+          digest: self.class.digest(tables.first.first.wedding)
+        )
       end
     end
 

config/routes.rb

@@ -37,7 +37,7 @@ Rails.application.routes.draw do
     resources :expenses, only: %i[index create update destroy] do
       get :summary, on: :collection
     end
-    resources :tables_arrangements, only: %i[index show]
+    resources :tables_arrangements, only: %i[index show create]
     resources :summary, only: :index
 
     root to: redirect("/%{slug}")

db/migrate/20250126091823_add_guests_digest_column_to_tables_arrangements.rb

@@ -0,0 +1,5 @@
+class AddGuestsDigestColumnToTablesArrangements < ActiveRecord::Migration[8.0]
+  def change
+    add_column :tables_arrangements, :digest, :uuid, null: false, default: 'gen_random_uuid()'
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2024_12_16_231415) do
+ActiveRecord::Schema[8.0].define(version: 2025_01_26_091823) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_catalog.plpgsql"
 
@@ -206,6 +206,7 @@ ActiveRecord::Schema[8.0].define(version: 2024_12_16_231415) do
     t.datetime "updated_at", null: false
     t.string "name", null: false
     t.uuid "wedding_id", null: false
+    t.uuid "digest", default: -> { "gen_random_uuid()" }, null: false
     t.index ["wedding_id"], name: "index_tables_arrangements_on_wedding_id"
   end
 

spec/requests/tables_arrangements_spec.rb

@@ -18,13 +18,27 @@ RSpec.describe 'tables_arrangements' do
                  properties: {
                    id: { type: :string, format: :uuid },
                    name: { type: :string },
-                   discomfort: { type: :integer }
+                   discomfort: { type: :integer },
+                   valid: { type: :boolean }
                  }
                }
         xit
       end
       regular_api_responses
     end
+
+    post('create tables arrangement') do
+      tags 'Tables Arrangements'
+      produces 'application/json'
+      parameter Swagger::Schema::SLUG
+      response(201, 'successful') do
+        schema type: :object,
+               required: [],
+               properties: {}
+        xit
+      end
+      regular_api_responses
+    end
   end
 
   path '/{slug}/tables_arrangements/{id}' do