Pre generate all URNs

app/models/urn.rb

@@ -1,38 +1,41 @@
-# frozen_string_literal: true
-
-# Urn represents a Uniform Resource Name (URN) generator.
-# It generates a URN with a fixed prefix and a random alphanumeric suffix.
-#
+# == Schema Information
 #
-# Example:
+# Table name: urns
 #
-#   Urn.generate('teacher')          # => "IRPTE12345"
-#   Urn.generate('teacher')          # => "IRPTE12345"
-#   Urn.generate('salaried_trainee') # => "IRPST12345"
+#  id         :bigint           not null, primary key
+#  code       :string
+#  prefix     :string
+#  suffix     :integer
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
 #
-class Urn
-  attr_reader :value
-  attr_writer :suffix
-
-  def self.generate(applicant_type)
-    code = applicant_type_code(applicant_type)
-    PREFIX + code + Array.new(LENGTH) { CHARSET.sample }.join
-  end
+class Urn < ApplicationRecord
+  class NoUrnAvailableError < StandardError; end
 
-  CHARSET = %w[0 1 2 3 4 5 6 7 8 9].freeze
-  PREFIX = "IRP"
-  LENGTH = 5
-  private_constant :CHARSET, :PREFIX, :LENGTH
+  PREFIX = "IRP".freeze
+  MAX_SUFFIX = 99_999
+  PADDING_SIZE = MAX_SUFFIX.to_s.size
+  VALID_CODES = {
+    "teacher" => "TE",
+    "salaried_trainee" => "ST",
+  }.freeze
 
-  def self.applicant_type_code(applicant_type)
-    case applicant_type
-    when "teacher"
-      "TE"
-    when "salaried_trainee"
-      "ST"
-    else
-      raise(ArgumentError, "Invalid applicant type: #{applicant_type}")
+  def self.next(route)
+    code = VALID_CODES.fetch(route)
+    Urn.transaction do
+      urn = find_by!(code:)
+      urn.destroy!
+      urn.to_s
     end
+  rescue KeyError => e
+    Sentry.capture_exception(e)
+    raise(ArgumentError, "Unknown route #{route}")
+  rescue ActiveRecord::RecordNotFound => e
+    Sentry.capture_exception(e)
+    raise(NoUrnAvailableError, "There no more unique URN available for #{route}")
+  end
+
+  def to_s
+    [prefix, code, sprintf("%0#{PADDING_SIZE}d", suffix)].join
   end
-  private_methods :applicant_type_code
 end

app/services/generate_urns.rb

@@ -0,0 +1,62 @@
+# Service responsible for the generation of all urns
+# It will save the set of available urns based the current URN format
+# and store it in the database URNs table.
+#
+# The Urn model will then be able to fetch the next available unique and
+# random urn for application submition
+#
+# Example:
+#
+#   Urn.next("teacher")          # => "IRPTE12345"
+#   Urn.next("teacher")          # => "IRPTE12345"
+#   Urn.next("salaried_trainee") # => "IRPST12345"
+#
+class GenerateUrns
+  def self.call
+    return if Urn.count.positive? # Do not override the current urn state
+
+    Urn.transaction do
+      Urn::VALID_CODES.each_value do |code|
+        new(code:).generate
+      end
+    end
+  end
+
+  def initialize(code:)
+    @code = code
+  end
+
+  attr_reader :code
+
+  def generate
+    data = unused_urns.map do |suffix|
+      { prefix: Urn::PREFIX, code: code, suffix: suffix }
+    end
+    Urn.insert_all(data) # rubocop:disable Rails/SkipsModelValidations
+  end
+
+private
+
+  def unused_urns
+    generate_suffixes - existing_suffixes
+  end
+
+  def generate_suffixes
+    Array
+      .new(Urn::MAX_SUFFIX) { _1 }
+      .drop(1)
+      .shuffle!
+  end
+
+  def existing_suffixes
+    route = Urn::VALID_CODES.key(code)
+    Application
+      .where(application_route: route)
+      .pluck(:urn)
+      .map { extract_suffix(_1) }
+  end
+
+  def extract_suffix(urn)
+    urn.match(/\d+/)[0].to_i
+  end
+end

app/services/submit_form.rb

@@ -88,7 +88,7 @@ def create_application
       date_of_entry: form.date_of_entry,
       start_date: form.start_date,
       subject: SubjectStep.new(form).answer.formatted_value,
-      urn: Urn.generate(form.application_route),
+      urn: Urn.next(form.application_route),
       visa_type: form.visa_type,
     )
   end

bin/app-startup.sh

@@ -7,6 +7,8 @@ set -e
 
 # run migrations
 bundle exec rails db:migrate
+# Front load urn generation
+bundle exec rake urn:generate
 
 # add seed data in review environment
 if [[ "$RAILS_ENV" = "review" || "$RAILS_ENV" = "development" ]]; then

db/migrate/20230927092305_create_urns.rb

@@ -0,0 +1,12 @@
+class CreateUrns < ActiveRecord::Migration[7.0]
+  def change
+    create_table :urns do |t|
+      t.string :prefix
+      t.string :code
+      t.integer :suffix
+
+      t.timestamps
+    end
+    add_index :urns, :code
+  end
+end

lib/tasks/urn.rake

@@ -0,0 +1,10 @@
+namespace :urn do
+  desc "generate and randomize unique urns"
+  task generate: :environment do
+    puts "running rake task urn:generate ..."
+    a = Urn.count
+    GenerateUrns.call
+    b = Urn.count
+    puts "#{b - a} URN created"
+  end
+end

spec/factories/applications.rb

@@ -31,7 +31,7 @@
     visa_type { VisaStep::VALID_ANSWERS_OPTIONS.reject { _1 == "Other" }.sample }
     date_of_entry { Time.zone.today }
     start_date { 1.month.from_now.to_date }
-    urn { Urn.generate(application_route) }
+    urn { Urn.next(application_route) }
 
     factory :teacher_application do
       application_route { "teacher" }

spec/factories/urns.rb

@@ -0,0 +1,7 @@
+FactoryBot.define do
+  factory :urn do
+    prefix { "IRP" }
+    code { %w[TE ST].sample }
+    suffix { Array.new(10) { _1 }.sample }
+  end
+end

spec/features/admin_console/applications_list_spec.rb

@@ -59,6 +59,8 @@
 
   def given_there_are_few_applications
     # Create 2 specific applications for search tests
+    create_list(:urn, 5, code: "TE")
+    create_list(:urn, 5, code: "ST")
     unique_applicant = create(:applicant, given_name: "Unique Given Name", middle_name: "Unique Middle Name", family_name: "Unique Family Name", email_address: "[email protected]")
     create(:application, applicant: unique_applicant, urn: "Unique Urn 1")
 
@@ -70,12 +72,16 @@ def given_there_are_few_applications
   end
 
   def given_there_is_an_application_that_breached_sla
+    create_list(:urn, 5, code: "TE")
+    create_list(:urn, 5, code: "ST")
     applicant = create(:applicant)
     application = create(:application, applicant:)
     application.application_progress.update(initial_checks_completed_at: 4.days.ago)
   end
 
   def given_there_are_applications_with_different_dates
+    create_list(:urn, 5, code: "TE")
+    create_list(:urn, 5, code: "ST")
     create(:application, application_progress: build(:application_progress, :initial_checks_completed, status: :initial_checks))
     create(:application, application_progress: build(:application_progress, :home_office_checks_completed, status: :home_office_checks))
   end

spec/fixtures/urns.yml

@@ -0,0 +1,90 @@
+te_one:
+  suffix: 5668
+  prefix: IRP
+  code: TE
+
+te_two:
+  suffix: 21368
+  prefix: IRP
+  code: TE
+
+te_three:
+  suffix: 5
+  prefix: IRP
+  code: TE
+
+te_four:
+  suffix: 76998
+  prefix: IRP
+  code: TE
+
+te_five:
+  suffix: 6559
+  prefix: IRP
+  code: TE
+
+te_six:
+  suffix: 6
+  prefix: IRP
+  code: TE
+
+te_seven:
+  suffix: 2298
+  prefix: IRP
+  code: TE
+
+te_eight:
+  suffix: 1159
+  prefix: IRP
+  code: TE
+
+te_nine:
+  suffix: 79298
+  prefix: IRP
+  code: TE
+
+te_ten:
+  suffix: 19549
+  prefix: IRP
+  code: TE
+
+st_one:
+  suffix: 5668
+  prefix: IRP
+  code: ST
+
+st_two:
+  suffix: 29968
+  prefix: IRP
+  code: ST
+
+st_three:
+  suffix: 5
+  prefix: IRP
+  code: ST
+
+st_four:
+  suffix: 76998
+  prefix: IRP
+  code: ST
+
+st_five:
+  suffix: 6559
+  prefix: IRP
+  code: ST
+
+st_six:
+  suffix: 6
+  prefix: IRP
+  code: ST
+
+st_seven:
+  suffix: 28
+  prefix: IRP
+  code: ST
+
+st_eight:
+  suffix: 159
+  prefix: IRP
+  code: ST
+