feat(cache.procedure_dossier_pagination): add Cache::ProcedureDossierPagination to next/previous dossiers by statut. also responsible to fetch next/previous page

app/models/cache/procedure_dossier_pagination.rb

@@ -0,0 +1,107 @@
+# frozen_string_literal: true
+
+class Cache::ProcedureDossierPagination
+  HALF_WINDOW = 50
+  TRESHOLD_BEFORE_REFRESH = 1
+  CACHE_EXPIRACY = 8.hours
+
+  attr_reader :procedure_presentation, :statut, :cache
+  delegate :procedure, :instructeur, to: :procedure_presentation
+
+  def initialize(procedure_presentation:, statut:)
+    @procedure_presentation = procedure_presentation
+    @statut = statut
+    @cache = Kredis.json(cache_key, expires_in: CACHE_EXPIRACY)
+  end
+
+  def save_context(ids:, incoming_page:)
+    value = { ids: }
+    value[:incoming_page] = incoming_page if incoming_page
+    write_cache(value)
+  end
+
+  def next_dossier_id(from_id:)
+    index = ids&.index(from_id.to_i)
+
+    return nil if index.nil? # not found
+
+    if refresh_cache_after?(from_id:)
+      renew_ids(from_id:)
+      index = ids.index(from_id.to_i)
+    end
+    return nil if index.blank?
+    return nil if index + 1 > ids.size # out of bound end
+
+    ids[index + 1]
+  end
+
+  def previous_dossier_id(from_id:)
+    index = ids&.index(from_id.to_i)
+
+    return nil if index.nil? # not found
+
+    if refresh_cache_before?(from_id:)
+      renew_ids(from_id:)
+      index = ids.index(from_id.to_i)
+    end
+    return nil if index.blank?
+    return nil if index - 1 < 0 # out of bound start
+
+    ids[index - 1]
+  end
+
+  def incoming_page
+    read_cache[:incoming_page]
+  end
+
+  # test only
+  def raw
+    read_cache
+  end
+
+  private
+
+  def cache_key
+    [procedure.id, instructeur.id, statut].join(":")
+  end
+
+  def write_cache(value)
+    cache.value = value
+    @read_cache = nil
+  end
+
+  def read_cache
+    @read_cache ||= Hash(cache.value).with_indifferent_access
+  end
+
+  def ids = read_cache[:ids]
+
+  def refresh_cache_after?(from_id:) = from_id.in?(ids.last(TRESHOLD_BEFORE_REFRESH))
+
+  def refresh_cache_before?(from_id:) = from_id.in?(ids.first(TRESHOLD_BEFORE_REFRESH))
+
+  def renew_ids(from_id:)
+    value = read_cache
+    value[:ids] = fetch_ids_around(from_id:)
+
+    write_cache(value)
+  end
+
+  def fetch_all_ids
+    dossiers = Dossier.where(groupe_instructeur_id: GroupeInstructeur.joins(:instructeurs, :procedure).where(procedure: procedure, instructeurs: [instructeur]).select(:id))
+    DossierFilterService.filtered_sorted_ids(dossiers, statut, procedure_presentation.filters_for(statut), procedure_presentation.sorted_column, instructeur, count: 0)
+  end
+
+  def fetch_ids_around(from_id:)
+    all_ids = fetch_all_ids
+    from_id_at = all_ids.index(from_id)
+
+    if from_id_at.present?
+      new_page_starts_at = [0, from_id_at - HALF_WINDOW].max # avoid index below 0
+      new_page_ends_at = [from_id_at + HALF_WINDOW, all_ids.size].min # avoid index above all_ids.size
+      all_ids.slice(new_page_starts_at, new_page_ends_at)
+    else
+      []
+    end
+  end
+end

spec/models/cache/procedure_dossier_pagination_spec.rb

@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+describe Cache::ProcedureDossierPagination do
+  let(:instructeur) { double(id: 1) }
+  let(:procedure) { double(id: 1) }
+  let(:procedure_presentation) { double(instructeur:, procedure:) }
+  let(:instance) { described_class.new(procedure_presentation:, statut: 'a-suivre') }
+
+  before do
+    instance.save_context(ids: cached_ids, incoming_page: nil)
+  end
+
+  describe 'next_dossier_id' do
+    context 'when procedure.dossiers.by_statut has only one page' do
+      let(:cached_ids) { [3, 4] }
+      before do
+        allow(instance).to receive(:fetch_all_ids).and_return(cached_ids)
+      end
+
+      it 'find next until the end' do
+        expect(instance.next_dossier_id(from_id: cached_ids.last)).to eq(nil)
+        expect(instance.next_dossier_id(from_id: cached_ids.first)).to eq(cached_ids.last)
+      end
+    end
+
+    context 'when procedure.dossiers.by_statut has more than one page' do
+      let(:cached_ids) { [2, 3, 4] }
+      let(:next_page_ids) { (0..10).to_a }
+
+      subject { instance.next_dossier_id(from_id: cached_ids.last) }
+      before do
+        allow(instance).to receive(:fetch_all_ids).and_return(next_page_ids)
+      end
+
+      it 'refreshes paginated_ids' do
+        expect { subject }.to change { instance.send(:ids) }.from(cached_ids).to(next_page_ids)
+      end
+    end
+
+    context 'when procedure.dossiers.by_statut does not include searched dossiers anymore' do
+      let(:cached_ids) { [] }
+      let(:next_page_ids) { [] }
+      before { allow(instance).to receive(:fetch_all_ids).and_return(next_page_ids) }
+
+      it 'works' do
+        expect(instance.next_dossier_id(from_id: 50)).to eq(nil)
+      end
+    end
+  end
+
+  describe 'previous_dossier_id' do
+    context 'when procedure.dossiers.by_statut has only one page' do
+      let(:cached_ids) { [3, 4] }
+      before do
+        allow(instance).to receive(:fetch_all_ids).and_return(cached_ids)
+      end
+
+      it 'find next until the end' do
+        expect(instance.previous_dossier_id(from_id: cached_ids.last)).to eq(cached_ids.first)
+        expect(instance.previous_dossier_id(from_id: cached_ids.first)).to eq(nil)
+      end
+    end
+
+    context 'when procedure.dossiers.by_statut has more than one page' do
+      let(:cached_ids) { [11, 12, 13] }
+      subject { instance.previous_dossier_id(from_id: cached_ids.first) }
+      let(:next_page_ids) { (11..20).to_a }
+      before do
+        allow(instance).to receive(:fetch_all_ids).and_return(next_page_ids)
+      end
+
+      it 'works' do
+        expect { subject }.to change { instance.send(:ids) }.from(cached_ids).to(next_page_ids)
+      end
+    end
+
+    context 'when procedure.dossiers.by_statut does not include searched dossiers anymore' do
+      let(:cached_ids) { [] }
+      before { allow(instance).to receive(:fetch_all_ids).and_return([]) }
+
+      it 'works' do
+        expect(instance.previous_dossier_id(from_id: 50)).to eq(nil)
+      end
+    end
+  end
+end