get all available zones at specific date

app/models/zone.rb

@@ -27,4 +27,8 @@ class Zone < ApplicationRecord
   def available_at?(date)
     label_at(date) != 'NA'
   end
+
+  def self.available_at(date)
+    Zone.all.filter { |zone| zone.available_at?(date) }.sort_by { |zone| zone.label_at(date) }
+  end
 end

spec/models/zone_spec.rb

@@ -65,5 +65,57 @@ describe Zone do
       expect(zone.available_at?(start_previous_government + 1.week)).to be_truthy
     end
   end
-end
 
+  describe "#self.available_at?" do
+    let(:start_previous_government) { Date.parse('2020-07-06') }
+    let(:start_last_government) { Date.parse('2022-05-20') }
+    let(:start_futur_government) { Date.parse('2027-05-20') }
+    let(:om) do
+      create(:zone, labels: [
+        {
+          designated_on: start_previous_government,
+          name: "Ministère des Outre-mer"
+        },
+        {
+          designated_on: start_last_government,
+          name: "NA"
+        },
+        {
+          designated_on: start_futur_government,
+          name: "Ministère des Territoires d'Outre-mer"
+        }
+      ])
+    end
+
+    let!(:culture) do
+      create(:zone, labels: [
+        {
+          designated_on: start_previous_government,
+          name: "Ministère de la Culture"
+        }
+      ])
+    end
+
+    let!(:om) do
+      create(:zone, labels: [
+        {
+          designated_on: start_previous_government,
+          name: "Ministère des Outre-mer"
+        },
+        {
+          designated_on: start_last_government,
+          name: "NA"
+        },
+        {
+          designated_on: start_futur_government,
+          name: "Ministère des Territoires d'Outre-mer"
+        }
+      ])
+    end
+
+    it 'returns only available zones at specific date' do
+      expect(Zone.available_at(start_last_government + 1.day)).to eq [culture]
+      expect(Zone.available_at(start_previous_government + 1.day)).to eq [culture, om]
+    end
+  end
+end