Do not create same Telegram user twice

app/controllers/telegram_bot_updates_controller.rb

@@ -28,13 +28,15 @@ private
   end
 
   def handle_user(user)
-    TelegramUser.create!(
-      remote_telegram_id: user[:id],
-      is_bot:             user[:is_bot],
-      first_name:         user[:first_name],
-      last_name:          user[:last_name],
-      username:           user[:username],
-      language_code:      user[:language_code],
-    )
+    telegram_user =
+      TelegramUser.find_or_initialize_by remote_telegram_id: user[:id]
+
+    telegram_user.is_bot        = user[:is_bot]
+    telegram_user.first_name    = user[:first_name]
+    telegram_user.last_name     = user[:last_name]
+    telegram_user.username      = user[:username]
+    telegram_user.language_code = user[:language_code]
+
+    telegram_user.save!
   end
 end

spec/requests/telegram_bot_updates/create_spec.rb

@@ -86,4 +86,55 @@ RSpec.describe 'POST /telegram_bot_updates' do
       end
     end
   end
+
+  context 'when message "from" attribute is set and ' \
+          'Telegram user already exist' do
+    let! :telegram_user do
+      create :telegram_user, remote_telegram_id: remote_telegram_id
+    end
+
+    def make_request
+      post '/telegram_bot_updates',
+           params: { telegram_bot_id: telegram_bot.id,
+                     secret:          telegram_bot.secret,
+                     message:         { from: telegram_user_attributes } }
+    end
+
+    let :telegram_user_attributes do
+      {
+        id:            remote_telegram_id,
+        is_bot:        is_bot,
+        first_name:    first_name,
+        last_name:     last_name,
+        username:      username,
+        language_code: language_code,
+      }
+    end
+
+    let(:remote_telegram_id) { rand 1..1_000_000 }
+    let(:is_bot) { [false, true].sample }
+    let(:first_name) { Faker::Name.first_name }
+    let(:last_name) { Faker::Name.last_name }
+    let(:username) { Faker::Internet.username }
+    let(:language_code) { I18n.available_locales.sample.to_s }
+
+    specify do
+      expect { make_request }.not_to change(TelegramUser, :count).from(1)
+    end
+
+    context 'after request' do
+      before { make_request }
+
+      specify do
+        expect(TelegramUser.last).to have_attributes(
+          remote_telegram_id: remote_telegram_id,
+          is_bot:             is_bot,
+          first_name:         first_name,
+          last_name:          last_name,
+          username:           username,
+          language_code:      language_code,
+        )
+      end
+    end
+  end
 end