add DossierProjectionService

app/services/dossier_projection_service.rb

@@ -0,0 +1,88 @@
+class DossierProjectionService
+  class DossierProjection < Struct.new(:dossier, :columns)
+  end
+
+  TABLE = 'table'
+  COLUMN = 'column'
+
+  # Returns [DossierProjection(dossier, columns)] ordered by dossiers_ids
+  # and the columns orderd by fields.
+  #
+  # It tries to be fast by using `pluck` (or at least `select`)
+  # to avoid deserializing entire records.
+  #
+  # It stores its intermediary queries results in an hash in the corresponding field.
+  # ex: field_email[:id_value_h] = { dossier_id_1: email_1, dossier_id_3: email_3 }
+  #
+  # Those hashes are needed because:
+  # - the order of the intermediary query results are unknown
+  # - some values can be missing (if a revision added or removed them)
+  def self.project(dossiers_ids, fields)
+    champ_fields, other_fields = fields
+      .partition { |f| ['type_de_champ', 'type_de_champ_private'].include?(f[TABLE]) }
+
+    if champ_fields.present?
+      Champ
+        .includes(:type_de_champ)
+        .where(
+          # as querying the champs table is costly
+          # we fetch all the requested champs at once
+          types_de_champ: { stable_id: champ_fields.map { |f| f[COLUMN] } },
+          dossier_id: dossiers_ids
+        )
+        .select(:dossier_id, :value, :type_de_champ_id, :stable_id) # we cannot pluck :value, as we need the champ.to_s method
+        .group_by(&:stable_id) # the champs are redispatched to their respective fields
+        .map do |stable_id, champs|
+        field = champ_fields.find { |f| f[COLUMN] == stable_id.to_s }
+        field[:id_value_h] = champs.to_h { |c| [c.dossier_id, c.to_s] }
+      end
+    end
+
+    other_fields.each do |field|
+      field[:id_value_h] = case field[TABLE]
+      when 'self'
+        Dossier
+          .where(id: dossiers_ids)
+          .pluck(:id, field[COLUMN].to_sym)
+          .to_h { |id, col| [id, col&.strftime('%d/%m/%Y')] }
+      when 'user'
+        Dossier
+          .joins(:user)
+          .where(id: dossiers_ids)
+          .pluck('dossiers.id, users.email')
+          .to_h
+      when 'individual'
+        Individual
+          .where(dossier_id: dossiers_ids)
+          .pluck(:dossier_id, field[COLUMN].to_sym)
+          .to_h
+      when 'etablissement'
+        Etablissement
+          .where(dossier_id: dossiers_ids)
+          .pluck(:dossier_id, field[COLUMN].to_sym)
+          .to_h
+      when 'groupe_instructeur'
+        Dossier
+          .joins(:groupe_instructeur)
+          .where(id: dossiers_ids)
+          .pluck('dossiers.id, groupe_instructeurs.label')
+          .to_h
+      when 'followers_instructeurs'
+        Follow
+          .active
+          .joins(instructeur: :user)
+          .where(dossier_id: dossiers_ids)
+          .pluck('dossier_id, users.email')
+          .group_by { |dossier_id, _| dossier_id }
+          .to_h { |dossier_id, dossier_id_emails| [dossier_id, dossier_id_emails.map { |_, email| email }&.join(', ')] }
+      end
+    end
+
+    Dossier
+      .select(:id, :state, :archived) # the dossier object is needed in the view
+      .find(dossiers_ids) # keeps dossiers_ids order and raise exception if one is missing
+      .map do |dossier|
+      DossierProjection.new(dossier, fields.map { |f| f[:id_value_h][dossier.id] })
+    end
+  end
+end