Use the friendly ID gem for contest slugs

Gemfile

@@ -43,6 +43,7 @@ gem "thruster", require: false
 gem "slim"
 gem "dartsass-rails"
 gem "bootstrap", "~> 5.3.3"
+gem "friendly_id", "~> 5.5.0"
 
 group :development, :test do
   # See https://guides.rubyonrails.org/debugging_rails_applications.html#debugging-with-the-debug-gem

Gemfile.lock

@@ -118,6 +118,8 @@ GEM
     et-orbi (1.2.11)
       tzinfo
     execjs (2.10.0)
+    friendly_id (5.5.1)
+      activerecord (>= 4.0.0)
     fugit (1.11.1)
       et-orbi (~> 1, >= 1.2.11)
       raabro (~> 1.4)
@@ -403,6 +405,7 @@ DEPENDENCIES
   capybara
   dartsass-rails
   debug
+  friendly_id (~> 5.5.0)
   importmap-rails
   jbuilder
   kamal

app/controllers/contests_controller.rb

@@ -84,6 +84,6 @@ class ContestsController < ApplicationController
   end
 
   def contest_params
-    params.expect(contest: [ :name, :team, :allow_registration, :slug ])
+    params.expect(contest: [ :name, :team, :allow_registration ])
   end
 end

app/models/contest.rb

@@ -13,6 +13,7 @@
 #
 # Indexes
 #
+#  index_contests_on_slug     (slug) UNIQUE
 #  index_contests_on_user_id  (user_id)
 #
 # Foreign Keys
@@ -20,12 +21,14 @@
 #  user_id  (user_id => users.id)
 #
 class Contest < ApplicationRecord
-  belongs_to :user
+  extend FriendlyId
 
+  belongs_to :user
   has_many :completions, dependent: :destroy
   has_many :contestants, dependent: :destroy
   has_many :puzzles, dependent: :destroy
 
+  friendly_id :name, use: :slugged
+
   validates :name, presence: true
-  validates :slug, presence: true, uniqueness: true, format: { with: /\A(\w|-)*\z/, message: 'Only alphanumeric characters, "-" and "_" allowed.' }
 end

app/views/contests/_form.html.slim

@@ -4,12 +4,6 @@
       .form-floating
         = form.text_field :name, autocomplete: "off", class: "form-control"
         = form.label :name, class: "required"
-  .row.mb-3
-    .col
-      .form-floating
-        = form.text_field :slug, autocomplete: "off", class: "form-control"
-        = form.label :slug, class: "required"
-      .form-text This will be used for building the public scoreboard URL: https://puzzle-scoreboard.org/public/<slug>.
   .row.mb-3
     .col
       .form-check.form-switch

config/initializers/friendly_id.rb

@@ -0,0 +1,107 @@
+# FriendlyId Global Configuration
+#
+# Use this to set up shared configuration options for your entire application.
+# Any of the configuration options shown here can also be applied to single
+# models by passing arguments to the `friendly_id` class method or defining
+# methods in your model.
+#
+# To learn more, check out the guide:
+#
+# http://norman.github.io/friendly_id/file.Guide.html
+
+FriendlyId.defaults do |config|
+  # ## Reserved Words
+  #
+  # Some words could conflict with Rails's routes when used as slugs, or are
+  # undesirable to allow as slugs. Edit this list as needed for your app.
+  config.use :reserved
+
+  config.reserved_words = %w[new edit index session login logout users admin
+    stylesheets assets javascripts images]
+
+  # This adds an option to treat reserved words as conflicts rather than exceptions.
+  # When there is no good candidate, a UUID will be appended, matching the existing
+  # conflict behavior.
+
+  config.treat_reserved_as_conflict = true
+
+  #  ## Friendly Finders
+  #
+  # Uncomment this to use friendly finders in all models. By default, if
+  # you wish to find a record by its friendly id, you must do:
+  #
+  #    MyModel.friendly.find('foo')
+  #
+  # If you uncomment this, you can do:
+  #
+  #    MyModel.find('foo')
+  #
+  # This is significantly more convenient but may not be appropriate for
+  # all applications, so you must explicitly opt-in to this behavior. You can
+  # always also configure it on a per-model basis if you prefer.
+  #
+  # Something else to consider is that using the :finders addon boosts
+  # performance because it will avoid Rails-internal code that makes runtime
+  # calls to `Module.extend`.
+
+  config.use :finders
+
+  # ## Slugs
+  #
+  # Most applications will use the :slugged module everywhere. If you wish
+  # to do so, uncomment the following line.
+
+  config.use :slugged
+
+  # By default, FriendlyId's :slugged addon expects the slug column to be named
+  # 'slug', but you can change it if you wish.
+  #
+  # config.slug_column = 'slug'
+  #
+  # By default, slug has no size limit, but you can change it if you wish.
+  #
+  # config.slug_limit = 255
+  #
+  # When FriendlyId can not generate a unique ID from your base method, it appends
+  # a UUID, separated by a single dash. You can configure the character used as the
+  # separator. If you're upgrading from FriendlyId 4, you may wish to replace this
+  # with two dashes.
+  #
+  # config.sequence_separator = '-'
+  #
+  # Note that you must use the :slugged addon **prior** to the line which
+  # configures the sequence separator, or else FriendlyId will raise an undefined
+  # method error.
+  #
+  #  ## Tips and Tricks
+  #
+  #  ### Controlling when slugs are generated
+  #
+  # As of FriendlyId 5.0, new slugs are generated only when the slug field is
+  # nil, but if you're using a column as your base method can change this
+  # behavior by overriding the `should_generate_new_friendly_id?` method that
+  # FriendlyId adds to your model. The change below makes FriendlyId 5.0 behave
+  # more like 4.0.
+  # Note: Use(include) Slugged module in the config if using the anonymous module.
+  # If you have `friendly_id :name, use: slugged` in the model, Slugged module
+  # is included after the anonymous module defined in the initializer, so it
+  # overrides the `should_generate_new_friendly_id?` method from the anonymous module.
+  #
+  # config.use :slugged
+  # config.use Module.new {
+  #   def should_generate_new_friendly_id?
+  #     slug.blank? || <your_column_name_here>_changed?
+  #   end
+  # }
+  #
+  # FriendlyId uses Rails's `parameterize` method to generate slugs, but for
+  # languages that don't use the Roman alphabet, that's not usually sufficient.
+  # Here we use the Babosa library to transliterate Russian Cyrillic slugs to
+  # ASCII. If you use this, don't forget to add "babosa" to your Gemfile.
+  #
+  # config.use Module.new {
+  #   def normalize_friendly_id(text)
+  #     text.to_slug.normalize! :transliterations => [:russian, :latin]
+  #   end
+  # }
+end

db/migrate/20250326162646_remove_slug_from_contests.rb

@@ -0,0 +1,5 @@
+class RemoveSlugFromContests < ActiveRecord::Migration[8.0]
+  def change
+    remove_column :contests, :slug, :string
+  end
+end

db/migrate/20250326162828_add_slug_to_contests.rb

@@ -0,0 +1,6 @@
+class AddSlugToContests < ActiveRecord::Migration[8.0]
+  def change
+    add_column :contests, :slug, :string
+    add_index :contests, :slug, unique: true
+  end
+end

db/migrate/20250326162920_create_friendly_id_slugs.rb

@@ -0,0 +1,21 @@
+MIGRATION_CLASS =
+  if ActiveRecord::VERSION::MAJOR >= 5
+    ActiveRecord::Migration["#{ActiveRecord::VERSION::MAJOR}.#{ActiveRecord::VERSION::MINOR}"]
+  else
+    ActiveRecord::Migration
+  end
+
+class CreateFriendlyIdSlugs < MIGRATION_CLASS
+  def change
+    create_table :friendly_id_slugs do |t|
+      t.string :slug, null: false
+      t.integer :sluggable_id, null: false
+      t.string :sluggable_type, limit: 50
+      t.string :scope
+      t.datetime :created_at
+    end
+    add_index :friendly_id_slugs, [ :sluggable_type, :sluggable_id ]
+    add_index :friendly_id_slugs, [ :slug, :sluggable_type ], length: { slug: 140, sluggable_type: 50 }
+    add_index :friendly_id_slugs, [ :slug, :sluggable_type, :scope ], length: { slug: 70, sluggable_type: 50, scope: 70 }, unique: true
+  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: 2025_03_26_153736) do
+ActiveRecord::Schema[8.0].define(version: 2025_03_26_162920) do
   create_table "active_storage_attachments", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -71,9 +71,21 @@ ActiveRecord::Schema[8.0].define(version: 2025_03_26_153736) do
     t.boolean "team", default: false
     t.boolean "allow_registration", default: false
     t.string "slug"
+    t.index ["slug"], name: "index_contests_on_slug", unique: true
     t.index ["user_id"], name: "index_contests_on_user_id"
   end
 
+  create_table "friendly_id_slugs", force: :cascade do |t|
+    t.string "slug", null: false
+    t.integer "sluggable_id", null: false
+    t.string "sluggable_type", limit: 50
+    t.string "scope"
+    t.datetime "created_at"
+    t.index ["slug", "sluggable_type", "scope"], name: "index_friendly_id_slugs_on_slug_and_sluggable_type_and_scope", unique: true
+    t.index ["slug", "sluggable_type"], name: "index_friendly_id_slugs_on_slug_and_sluggable_type"
+    t.index ["sluggable_type", "sluggable_id"], name: "index_friendly_id_slugs_on_sluggable_type_and_sluggable_id"
+  end
+
   create_table "puzzles", force: :cascade do |t|
     t.string "name"
     t.datetime "created_at", null: false

test/fixtures/contests.yml

@@ -15,6 +15,7 @@
 #
 # Indexes
 #
+#  index_contests_on_slug     (slug) UNIQUE
 #  index_contests_on_user_id  (user_id)
 #
 # Foreign Keys

test/models/contest_test.rb

@@ -13,6 +13,7 @@
 #
 # Indexes
 #
+#  index_contests_on_slug     (slug) UNIQUE
 #  index_contests_on_user_id  (user_id)
 #
 # Foreign Keys