siret champ can fetch it's own etablissement

app/models/champs/siret_champ.rb

@@ -21,6 +21,8 @@
 #  type_de_champ_id               :integer
 #
 class Champs::SiretChamp < Champ
+  include SiretChampEtablissementFetchableConcern
+
   def search_terms
     etablissement.present? ? etablissement.search_terms : [value]
   end

app/models/concerns/siret_champ_etablissement_fetchable_concern.rb

@@ -0,0 +1,34 @@
+module SiretChampEtablissementFetchableConcern
+  extend ActiveSupport::Concern
+
+  def fetch_etablissement!(siret, user)
+    return clear if siret.empty?
+    return clear(error: :invalid) unless Siret.new(siret: siret).valid? # i18n-tasks-use t('errors.messages.invalid_siret')
+    return clear(error: :not_found) unless (etablissement = APIEntrepriseService.create_etablissement(self, siret, user.id)) # i18n-tasks-use t('errors.messages.siret_not_found')
+
+    return update_etablissement!(etablissement)
+  rescue => error
+    if error.try(:network_error?) && !APIEntrepriseService.api_up?
+      # TODO: notify ops
+      etablissement = APIEntrepriseService.create_etablissement_as_degraded_mode(self, siret, user.id)
+      return update_etablissement!(etablissement, error: :api_entreprise_down)
+    else
+      Sentry.capture_exception(error, extra: { dossier_id: dossier_id, siret: siret })
+      return clear(error: :network_error) # i18n-tasks-use t('errors.messages.siret_network_error')
+    end
+  end
+
+  private
+
+  def update_etablissement!(etablissement, error: nil)
+    update!(value: etablissement.siret, etablissement: etablissement)
+    error.presence || etablissement.siret
+  end
+
+  def clear(error: nil)
+    etablissement_to_destroy = etablissement
+    update!(value: '', etablissement: nil)
+    etablissement_to_destroy&.destroy
+    error.presence
+  end
+end

spec/models/concern/siret_champ_etablissement_fetchable_concern_spec.rb

@@ -0,0 +1,94 @@
+RSpec.describe SiretChampEtablissementFetchableConcern do
+  describe '.fetch_etablissement!' do
+    let(:api_etablissement_status) { 200 }
+    let(:api_etablissement_body) { File.read('spec/fixtures/files/api_entreprise/etablissements.json') }
+    let(:token_expired) { false }
+    let!(:champ) { create(:champ_siret) }
+
+    before do
+      stub_request(:get, /https:\/\/entreprise.api.gouv.fr\/v2\/etablissements\/#{siret}/)
+        .to_return(status: api_etablissement_status, body: api_etablissement_body)
+      allow_any_instance_of(APIEntrepriseToken).to receive(:roles)
+        .and_return(["attestations_fiscales", "attestations_sociales", "bilans_entreprise_bdf"])
+      allow_any_instance_of(APIEntrepriseToken).to receive(:expired?).and_return(token_expired)
+    end
+
+    subject(:fetch_etablissement!) { champ.fetch_etablissement!(siret, build_stubbed(:user)) }
+
+    shared_examples 'an error occured' do |error|
+      it { expect { fetch_etablissement! }.to change { champ.reload.value }.to('') }
+
+      it { expect { fetch_etablissement! }.to change { champ.reload.etablissement }.to(nil) }
+
+      it { expect { fetch_etablissement! }.to change { Etablissement.count }.by(-1) }
+
+      it { expect(fetch_etablissement!).to eq(error) }
+    end
+
+    context 'when the SIRET is empty' do
+      let(:siret) { '' }
+
+      it_behaves_like 'an error occured', nil
+    end
+
+    context 'when the SIRET is invalid' do
+      let(:siret) { '1234' }
+
+      it_behaves_like 'an error occured', :invalid
+    end
+
+    context 'when the API is unavailable due to network error' do
+      let(:siret) { '82161143100015' }
+      let(:api_etablissement_status) { 503 }
+
+      before { expect(APIEntrepriseService).to receive(:api_up?).and_return(true) }
+
+      it_behaves_like 'an error occured', :network_error
+
+      it 'sends the error to Sentry' do
+        expect(Sentry).to receive(:capture_exception)
+        fetch_etablissement!
+      end
+    end
+
+    context 'when the API is unavailable due to an api maintenance or pb' do
+      let(:siret) { '82161143100015' }
+      let(:api_etablissement_status) { 502 }
+
+      before { expect(APIEntrepriseService).to receive(:api_up?).and_return(false) }
+
+      it { expect { fetch_etablissement! }.to change { champ.reload.value }.to(siret) }
+
+      it { expect { fetch_etablissement! }.to change { champ.reload.etablissement } }
+
+      it { expect { fetch_etablissement! }.to change { champ.reload.etablissement.as_degraded_mode? }.to(true) }
+
+      it { expect { fetch_etablissement! }.to change { Etablissement.count }.by(1) }
+
+      it { expect(fetch_etablissement!).to eq(:api_entreprise_down) }
+    end
+
+    context 'when the SIRET is valid but unknown' do
+      let(:siret) { '00000000000000' }
+      let(:api_etablissement_status) { 404 }
+
+      it_behaves_like 'an error occured', :not_found
+    end
+
+    context 'when the SIRET informations are retrieved successfully' do
+      let(:siret) { '41816609600051' }
+      let(:api_etablissement_status) { 200 }
+      let(:api_etablissement_body) { File.read('spec/fixtures/files/api_entreprise/etablissements.json') }
+
+      it { expect { fetch_etablissement! }.to change { champ.reload.value }.to(siret) }
+
+      it { expect { fetch_etablissement! }.to change { champ.reload.etablissement.siret }.to(siret) }
+
+      it { expect { fetch_etablissement! }.to change { champ.reload.etablissement.naf }.to("6202A") }
+
+      it { expect { fetch_etablissement! }.to change { Etablissement.count }.by(1) }
+
+      it { expect(fetch_etablissement!).to eq(siret) }
+    end
+  end
+end