Add support for FASP data sharing (#34415)

app/models/fasp/backfill_request.rb

@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: fasp_backfill_requests
+#
+#  id               :bigint(8)        not null, primary key
+#  category         :string           not null
+#  cursor           :string
+#  fulfilled        :boolean          default(FALSE), not null
+#  max_count        :integer          default(100), not null
+#  created_at       :datetime         not null
+#  updated_at       :datetime         not null
+#  fasp_provider_id :bigint(8)        not null
+#
+class Fasp::BackfillRequest < ApplicationRecord
+  belongs_to :fasp_provider, class_name: 'Fasp::Provider'
+
+  validates :category, presence: true, inclusion: Fasp::DATA_CATEGORIES
+  validates :max_count, presence: true,
+                        numericality: { only_integer: true }
+
+  after_commit :queue_fulfillment_job, on: :create
+
+  def next_objects
+    @next_objects ||= base_scope.to_a
+  end
+
+  def next_uris
+    next_objects.map { |o| ActivityPub::TagManager.instance.uri_for(o) }
+  end
+
+  def more_objects_available?
+    return false if next_objects.empty?
+
+    base_scope.where(id: ...(next_objects.last.id)).any?
+  end
+
+  def advance!
+    if more_objects_available?
+      update!(cursor: next_objects.last.id)
+    else
+      update!(fulfilled: true)
+    end
+  end
+
+  private
+
+  def base_scope
+    result = category_scope.limit(max_count).order(id: :desc)
+    result = result.where(id: ...cursor) if cursor.present?
+    result
+  end
+
+  def category_scope
+    case category
+    when 'account'
+      Account.discoverable.without_instance_actor
+    when 'content'
+      Status.indexable
+    end
+  end
+
+  def queue_fulfillment_job
+    Fasp::BackfillWorker.perform_async(id)
+  end
+end