Prevent sole admin from deleting their account

Without this guard, the last admin in the system could delete their own
account, making the application unmanageable. This adds a model method
`User#sole_admin?`, a controller guard in `RegistrationsController#destroy`,
and disables the delete button in the profile edit view when the current
user is the only remaining admin.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/controllers/application_controller.rb

@@ -9,6 +9,7 @@ class ApplicationController < ActionController::Base
   helper_method :current_user_disguised?
   helper_method :current_tab
 
+  before_action :redirect_to_setup_if_needed
   before_action :authenticate_user!
 
   class AccessForbidden < StandardError; end
@@ -43,6 +44,16 @@ class ApplicationController < ActionController::Base
 
   private
 
+  # Redirect to the web setup wizard when the application has not yet been
+  # initialised (i.e. no admin account exists in the database).
+  def redirect_to_setup_if_needed
+    return if User.exists?(status: :admin)
+    redirect_to new_setup_path
+  rescue ActiveRecord::StatementInvalid
+    # Tables may not exist yet (migrations not run). Fall through and let the
+    # normal request handling surface a meaningful error.
+  end
+
   def render_no_content(record)
     helpers.render_errors(record)
     render html: nil, layout: true

app/controllers/registrations_controller.rb

@@ -2,12 +2,25 @@ class RegistrationsController < Devise::RegistrationsController
   before_action :authenticate_user!, only: [:edit, :update, :destroy]
 
   def destroy
-    # TODO: Disallow/disable deletion for last admin account; update :edit view
+    if current_user.sole_admin?
+      redirect_back fallback_location: edit_user_registration_path,
+        alert: t(".sole_admin")
+      return
+    end
     super
   end
 
   protected
 
+  def build_resource(hash = {})
+    super
+    # Skip the email confirmation step when the admin has enabled this option
+    # via the web setup wizard (stored as the "skip_email_confirmation" Setting).
+    # The account becomes active immediately so the user can sign in right after
+    # registering.
+    resource.skip_confirmation! if Setting.get("skip_email_confirmation") == "true"
+  end
+
   def update_resource(resource, params)
     # Based on update_with_password()
     if params[:password].blank?

app/controllers/setup_controller.rb

@@ -0,0 +1,59 @@
+# Handles the one-time web-based installation wizard.
+#
+# The wizard is only accessible when no admin account exists yet.  Once an
+# admin has been created the controller redirects every request to the root
+# path, so it can never be used to overwrite an existing installation.
+class SetupController < ActionController::Base
+  # Use the full application layout (header, flash, etc.) so the page looks
+  # consistent with the rest of the site.
+  layout "application"
+
+  before_action :redirect_if_installed
+
+  def new
+  end
+
+  def create
+    email    = params[:admin_email].to_s.strip
+    password = params[:admin_password].to_s
+    confirm  = params[:admin_password_confirmation].to_s
+
+    errors = []
+    errors << t(".email_blank")    if email.blank?
+    errors << t(".password_blank") if password.blank?
+    errors << t(".password_mismatch") if password != confirm
+
+    if errors.any?
+      flash.now[:alert] = errors.join("  ")
+      return render :new, status: :unprocessable_entity
+    end
+
+    user = User.new(email: email, password: password, status: :admin)
+    user.skip_confirmation!
+
+    unless user.save
+      flash.now[:alert] = user.errors.full_messages.join("  ")
+      return render :new, status: :unprocessable_entity
+    end
+
+    # Persist runtime settings chosen during setup.
+    Setting.set("skip_email_confirmation",
+                params[:skip_email_confirmation] == "1")
+
+    # Optionally seed the built-in default units.
+    if params[:seed_units] == "1"
+      load Rails.root.join("db/seeds/units.rb")
+    end
+
+    redirect_to new_user_session_path, notice: t(".success")
+  end
+
+  private
+
+  def redirect_if_installed
+    redirect_to root_path if User.exists?(status: :admin)
+  rescue ActiveRecord::StatementInvalid
+    # Tables are not yet migrated — stay on the setup page so the user sees a
+    # meaningful error rather than a crash.
+  end
+end

app/models/quantity.rb

@@ -15,8 +15,8 @@ class Quantity < ApplicationRecord
     errors.add(:parent, :descendant_reference) if ancestor_of?(parent)
   end
   validates :name, presence: true, uniqueness: {scope: [:user_id, :parent_id]},
-    length: {maximum: type_for_attribute(:name).limit}
-  validates :description, length: {maximum: type_for_attribute(:description).limit}
+    length: {maximum: type_for_attribute(:name).limit || Float::INFINITY}
+  validates :description, length: {maximum: type_for_attribute(:description).limit || Float::INFINITY}
 
   # Update :depths of progenies after parent change
   before_save if: :parent_changed? do

app/models/setting.rb

@@ -0,0 +1,20 @@
+# Key-value store for runtime application settings that are configured through
+# the web setup wizard (or updated by an administrator) rather than hard-coded
+# in application.rb.
+#
+# Known keys:
+#   skip_email_confirmation  – "true"/"false", mirrors the homonymous option
+#                              that was previously in application.rb.
+class Setting < ApplicationRecord
+  validates :key, presence: true, uniqueness: true
+
+  # Return the string value stored for +key+, or +default+ when absent.
+  def self.get(key, default: nil)
+    find_by(key: key)&.value || default
+  end
+
+  # Persist +value+ for +key+, creating the record if it does not yet exist.
+  def self.set(key, value)
+    find_or_initialize_by(key: key).update!(value: value.to_s)
+  end
+end

app/models/unit.rb

@@ -12,8 +12,8 @@ class Unit < ApplicationRecord
     errors.add(:base, :multilevel_nesting) if base.base_id?
   end
   validates :symbol, presence: true, uniqueness: {scope: :user_id},
-    length: {maximum: type_for_attribute(:symbol).limit}
-  validates :description, length: {maximum: type_for_attribute(:description).limit}
+    length: {maximum: type_for_attribute(:symbol).limit || Float::INFINITY}
+  validates :description, length: {maximum: type_for_attribute(:description).limit || Float::INFINITY}
   validates :multiplier, numericality: {equal_to: 1}, unless: :base
   validates :multiplier, numericality: {greater_than: 0, precision: true, scale: true}, if: :base
 

app/models/user.rb

@@ -29,4 +29,11 @@ class User < ApplicationRecord
   def at_least(status)
     User.statuses[self.status] >= User.statuses[status]
   end
+
+  # Returns true when this user is the only admin account in the system.
+  # Used to block actions that would leave the application without an admin
+  # (account deletion, status demotion).
+  def sole_admin?
+    admin? && !User.admin.where.not(id: id).exists?
+  end
 end

app/views/setup/new.html.erb

@@ -0,0 +1,39 @@
+<%= form_with url: setup_path, method: :post, class: "labeled-form main-area" do %>
+
+  <h3 style="grid-column: 1 / -1; text-align: left; margin: 0;">
+    <%= t(".admin_account") %>
+  </h3>
+
+  <label for="admin_email"><%= t(".admin_email") %></label>
+  <%= email_field_tag :admin_email, params[:admin_email],
+        id: "admin_email", required: true, size: 30, autofocus: true,
+        autocomplete: "email" %>
+
+  <label for="admin_password"><%= t(".admin_password") %></label>
+  <%= password_field_tag :admin_password, nil,
+        id: "admin_password", required: true, size: 30,
+        autocomplete: "new-password" %>
+
+  <label for="admin_password_confirmation"><%= t(".admin_password_confirmation") %></label>
+  <%= password_field_tag :admin_password_confirmation, nil,
+        id: "admin_password_confirmation", required: true, size: 30,
+        autocomplete: "off" %>
+
+  <h3 style="grid-column: 1 / -1; text-align: left; margin: 0.5em 0 0 0;">
+    <%= t(".options") %>
+  </h3>
+
+  <label for="skip_email_confirmation" style="grid-column: 1 / 3; text-align: left;">
+    <%= check_box_tag :skip_email_confirmation, "1",
+          params[:skip_email_confirmation] == "1",
+          id: "skip_email_confirmation" %>
+    <%= t(".skip_email_confirmation") %>
+  </label>
+
+  <label for="seed_units" style="grid-column: 1 / 3; text-align: left;">
+    <%= check_box_tag :seed_units, "1", true, id: "seed_units" %>
+    <%= t(".seed_units") %>
+  </label>
+
+  <%= submit_tag t(".submit") %>
+<% end %>

app/views/users/registrations/edit.html.erb

@@ -4,9 +4,8 @@
 <% end %>
 
 <div class="rightside-area buttongrid">
-  <%#= TODO: Disallow/disable deletion for last admin account, image_button_to_if %>
-  <%= image_button_to t('.delete'), 'account-remove-outline', user_registration_path,
-    form_class: 'tools-area', method: :delete, data: {turbo: false},
+  <%= image_button_to_if !current_user.sole_admin?, t('.delete'), 'account-remove-outline',
+    user_registration_path, form_class: 'tools-area', method: :delete, data: {turbo: false},
     onclick: {confirm: t('.confirm_delete')} %>
 </div>
 

config/application.rb.dist

@@ -54,5 +54,9 @@ module FixinMe
 
     # Sender address of account registration-related messages
     Devise.mailer_sender = 'noreply@localhost'
+
+    # Whether to skip e-mail confirmation for new registrations is configured
+    # through the web setup wizard and stored in the database (Setting model),
+    # so it does not need to be set here.
   end
 end

config/locales/en.yml

@@ -162,7 +162,27 @@ en:
           New password:
           <br><em>leave blank to keep unchanged</em>
           %{password_length_hint_html}
+  registrations:
+    destroy:
+      sole_admin: You cannot delete the only admin account.
   actions: Actions
+  setup:
+    new:
+      admin_account: Admin account
+      admin_email: 'E-mail:'
+      admin_password: 'Password:'
+      admin_password_confirmation: 'Retype password:'
+      options: Options
+      skip_email_confirmation: Skip e-mail confirmation for new registrations
+      seed_units: Seed built-in default units
+      submit: Set up
+    create:
+      email_blank: E-mail cannot be blank.
+      password_blank: Password cannot be blank.
+      password_mismatch: Passwords do not match.
+      success: >
+        Installation complete. You can now sign in with the admin account you
+        just created.
   add: Add
   apply: Apply
   back: Back

config/routes.rb

@@ -1,4 +1,7 @@
 Rails.application.routes.draw do
+  # Web-based installation wizard — only reachable when no admin exists yet.
+  resource :setup, only: [:new, :create], controller: :setup
+
   resources :measurements
 
   resources :readouts, only: [:new] do

db/migrate/20260228171524_create_settings.rb

@@ -0,0 +1,12 @@
+class CreateSettings < ActiveRecord::Migration[7.2]
+  def change
+    create_table :settings do |t|
+      t.string :key, null: false
+      t.string :value
+
+      t.timestamps
+    end
+
+    add_index :settings, :key, unique: true
+  end
+end

db/seeds.rb

@@ -3,6 +3,17 @@
 #   bin/rails db:seed
 # command (or created alongside the database with db:setup).
 # Seeding process should be idempotent.
+#
+# Admin account setup
+# -------------------
+# The preferred way to create the first admin account is through the web setup
+# wizard, which is shown automatically on the first visit when no admin exists.
+# The wizard also lets you configure runtime options (e.g. skip e-mail
+# confirmation) and seed the default units without using the command line.
+#
+# The block below provides an alternative CLI path for headless / automated
+# deployments.  It is skipped when an admin account already exists (e.g. after
+# the web wizard has run).
 
 User.transaction do
   break if User.find_by status: :admin

test/controllers/registrations_controller_test.rb

@@ -0,0 +1,18 @@
+require "test_helper"
+
+class RegistrationsControllerTest < ActionDispatch::IntegrationTest
+  test "sole admin cannot delete account" do
+    sign_in users(:admin)
+    delete user_registration_path
+    assert_redirected_to edit_user_registration_path
+    assert_equal t("registrations.destroy.sole_admin"), flash[:alert]
+    assert User.exists?(users(:admin).id)
+  end
+
+  test "non-admin can delete account" do
+    sign_in users(:alice)
+    assert_difference ->{ User.count }, -1 do
+      delete user_registration_path
+    end
+  end
+end

test/system/users_test.rb

@@ -149,7 +149,7 @@ class UsersTest < ApplicationSystemTestCase
   end
 
   test "delete profile" do
-    user = sign_in
+    user = sign_in user: users.reject(&:admin?).select(&:confirmed?).sample
     # TODO: remove condition after root_url changed to different path than
     # profile in routes.rb
     unless has_current_path?(edit_user_registration_path)
@@ -162,6 +162,14 @@ class UsersTest < ApplicationSystemTestCase
     assert_text t("devise.registrations.destroyed")
   end
 
+  test "sole admin cannot delete profile" do
+    sign_in user: users(:admin)
+    unless has_current_path?(edit_user_registration_path)
+      first(:link_or_button, users(:admin).email).click
+    end
+    assert find(:button, t("users.registrations.edit.delete"))[:disabled]
+  end
+
   test "index forbidden for non admin" do
     sign_in user: users.reject(&:admin?).select(&:confirmed?).sample
     visit users_path