launch merge process if an unlinked DS account with the same email exists

app/controllers/france_connect/particulier_controller.rb

@@ -13,9 +13,15 @@ class FranceConnect::ParticulierController < ApplicationController
     fci = FranceConnectService.find_or_retrieve_france_connect_information(params[:code])
 
     if fci.user.nil?
-      fci.associate_user!(fci.email_france_connect)
-    end
+      preexisting_unlinked_user = User.find_by(email: fci.email_france_connect.downcase)
 
+      if preexisting_unlinked_user.nil?
+        fci.associate_user!(fci.email_france_connect)
+        connect_france_connect_particulier(fci.user)
+      else
+        redirect_to france_connect_particulier_merge_path(fci.create_merge_token!)
+      end
+    else
       user = fci.user
 
       if user.can_france_connect?
@@ -24,12 +30,16 @@ class FranceConnect::ParticulierController < ApplicationController
         fci.destroy
         redirect_to new_user_session_path, alert: t('errors.messages.france_connect.forbidden_html', reset_link: new_user_password_path)
       end
+    end
 
   rescue Rack::OAuth2::Client::Error => e
     Rails.logger.error e.message
     redirect_france_connect_error_connection
   end
 
+  def merge
+  end
+
   private
 
   def redirect_to_login_if_fc_aborted

app/views/france_connect/particulier/merge.html.haml

@@ -0,0 +1,5 @@
+= content_for :title, "Fusion des comptes FC et #{APPLICATION_NAME}"
+
+.container
+  %h1.page-title Fusion des comptes FranceConnect et #{APPLICATION_NAME}
+

config/routes.rb

@@ -124,6 +124,7 @@ Rails.application.routes.draw do
   namespace :france_connect do
     get 'particulier' => 'particulier#login'
     get 'particulier/callback' => 'particulier#callback'
+    get 'particulier/merge/:merge_token' => 'particulier#merge', as: :particulier_merge
   end
 
   namespace :champs do

spec/controllers/france_connect/particulier_controller_spec.rb

@@ -1,6 +1,6 @@
 describe FranceConnect::ParticulierController, type: :controller do
   let(:birthdate) { '20150821' }
-  let(:email) { 'email_from_fc@test.com' }
+  let(:email) { 'EMAIL_from_fc@test.com' }
 
   let(:user_info) do
     {
@@ -50,7 +50,7 @@ describe FranceConnect::ParticulierController, type: :controller do
       end
 
       context 'when france_connect_particulier_id exists in database' do
-        let!(:fci) { FranceConnectInformation.create!(user_info.merge(user_id: fc_user.id)) }
+        let!(:fci) { FranceConnectInformation.create!(user_info.merge(user_id: fc_user&.id)) }
 
         context 'and is linked to an user' do
           let(:fc_user) { create(:user, email: 'associated_user@a.com') }
@@ -81,6 +81,32 @@ describe FranceConnect::ParticulierController, type: :controller do
             expect(flash[:alert]).to be_present
           end
         end
+
+        context 'and is not linked to an user' do
+          let(:fc_user) { nil }
+
+          context 'and no user with the same email exists' do
+            it 'creates an user with the same email and log in' do
+              expect { subject }.to change { User.count }.by(1)
+
+              user = User.last
+
+              expect(user.email).to eq(email.downcase)
+              expect(controller.current_user).to eq(user)
+              expect(response).to redirect_to(root_path)
+            end
+          end
+
+          context 'and an user with the same email exists' do
+            let!(:preexisting_user) { create(:user, email: email) }
+
+            it 'redirects to the merge process' do
+              expect { subject }.not_to change { User.count }
+
+              expect(response).to redirect_to(france_connect_particulier_merge_path(fci.reload.merge_token))
+            end
+          end
+        end
       end
 
       context 'when france_connect_particulier_id does not exist in database' do