Contestant 3: ID is a short random string

app/models/repository.rb

@@ -15,6 +15,7 @@ class Repository < ApplicationRecord
   validates :local_path, presence: true
 
   before_destroy :ensure_destroy_possible
+  before_create :set_unique_id
 
   class << self
 
@@ -40,8 +41,28 @@ def change_mirroring!(mirroring_enabled)
     update_column(:mirroring_enabled, mirroring_enabled)
   end
 
+  def self.generate_unique_id
+    (0...5).map { (97 + rand(26)).chr }.join
+  end
+
   private
 
+  def set_unique_id
+    return unless (custom? && !unique_id)
+    generated_id = nil
+    repo = nil
+
+    5.times do
+      generated_id = self.class.generate_unique_id
+      repo = Repository.find_by(unique_id: generated_id)
+      break unless repo
+    end
+
+    raise 'Can not generate unique custom repo ID' if repo
+
+    self.unique_id = generated_id
+  end
+
   def ensure_destroy_possible
     throw(:abort) unless custom?
   end

app/services/repository_service.rb

@@ -21,12 +21,6 @@ def create_repository!(product, url, attributes, custom: false)
       attach_product!(product, repository) unless product.nil?
     end
 
-    # FIXME: this is a hack to add some not nice ID value
-    if custom
-      repository.unique_id = "hack#{repository.id}"
-      repository.save!
-    end
-
     repository
   end
 

spec/factories/repositories.rb

@@ -19,6 +19,7 @@
 
     trait :custom do
       custom true
+      unique_id nil
     end
 
     trait :with_products do

spec/models/repository_spec.rb

@@ -55,4 +55,31 @@
     it(:handles_subpath) { expect(Repository.make_local_path('http://localhost.com/foo/bar')).to eq('/foo/bar') }
     it(:handles_subpath_trailing_slash) { expect(Repository.make_local_path('http://localhost.com/foo/bar/')).to eq('/foo/bar/') }
   end
+
+  describe '#set_unique_id' do
+    context 'assigns generated id to the custom repo' do
+      subject { create :repository, :custom, external_url: 'http://example.com/test1/' }
+
+      before do
+        expect(Repository).to receive(:generate_unique_id).and_return('abcde')
+      end
+
+      its(:unique_id) { is_expected.to eq('abcde') }
+    end
+
+    context "when can't generate the ID" do
+      let(:first_repo) { create :repository, :custom, external_url: 'http://example.com/test1/' }
+
+      before do
+        expect(Repository).to receive(:generate_unique_id).exactly(6).times.and_return('abcde')
+        first_repo
+      end
+
+      it 'raises an exception' do
+        expect do
+          create :repository, :custom, external_url: 'http://example.com/test2/'
+        end.to raise_error 'Can not generate unique custom repo ID'
+      end
+    end
+  end
 end