Sap system restore domain

lib/trento/domain/sap_system/events/sap_system_restored.ex

@@ -0,0 +1,17 @@
+defmodule Trento.Domain.Events.SapSystemRestored do
+  @moduledoc """
+  This event is emitted when a sap system is restored.
+  """
+
+  use Trento.Event
+
+  require Trento.Domain.Enums.Health, as: Health
+
+  defevent do
+    field :sap_system_id, Ecto.UUID
+    field :sid, :string
+    field :tenant, :string
+    field :db_host, :string
+    field :health, Ecto.Enum, values: Health.values()
+  end
+end

lib/trento/domain/sap_system/sap_system.ex

@@ -79,6 +79,7 @@ defmodule Trento.Domain.SapSystem do
     SapSystemDeregistered,
     SapSystemHealthChanged,
     SapSystemRegistered,
+    SapSystemRestored,
     SapSystemRolledUp,
     SapSystemRollUpRequested,
     SapSystemTombstoned,
@@ -238,6 +239,27 @@ defmodule Trento.Domain.SapSystem do
     |> Multi.execute(&maybe_emit_sap_system_health_changed_event/1)
   end
 
+  # Restore sap system
+  # Same registration rules
+  def execute(
+        %SapSystem{deregistered_at: deregistered_at} = sap_system,
+        %RegisterApplicationInstance{} = instance
+      )
+      when not is_nil(deregistered_at) do
+    sap_system
+    |> Multi.new()
+    |> Multi.execute(fn sap_system ->
+      emit_application_instance_registered_or_application_instance_health_changed(
+        sap_system,
+        instance
+      )
+    end)
+    |> Multi.execute(fn sap_system ->
+      maybe_emit_sap_system_restored_event(sap_system, instance)
+    end)
+    |> Multi.execute(&maybe_emit_sap_system_health_changed_event/1)
+  end
+
   # SAP system not registered, application already present
   # If the instance is not one of MESSAGESERVER or ABAP we discard.
   # Otherwise if the instance we want register together with already present instances
@@ -668,6 +690,18 @@ defmodule Trento.Domain.SapSystem do
     }
   end
 
+  def apply(%SapSystem{} = sap_system, %SapSystemRestored{
+        sid: sid,
+        health: health
+      }) do
+    %SapSystem{
+      sap_system
+      | sid: sid,
+        health: health,
+        deregistered_at: nil
+    }
+  end
+
   def apply(%SapSystem{} = sap_system, %SapSystemTombstoned{}), do: sap_system
 
   defp maybe_emit_database_instance_registered_event(
@@ -848,6 +882,27 @@ defmodule Trento.Domain.SapSystem do
     end
   end
 
+  defp maybe_emit_sap_system_restored_event(
+         %SapSystem{application: %Application{instances: instances}},
+         %RegisterApplicationInstance{
+           sap_system_id: sap_system_id,
+           sid: sid,
+           tenant: tenant,
+           db_host: db_host,
+           health: health
+         }
+       ) do
+    if instances_have_abap?(instances) and instances_have_messageserver?(instances) do
+      %SapSystemRestored{
+        db_host: db_host,
+        health: health,
+        sap_system_id: sap_system_id,
+        sid: sid,
+        tenant: tenant
+      }
+    end
+  end
+
   defp maybe_emit_sap_system_registered_or_updated_event(
          %SapSystem{sid: nil, application: %Application{instances: instances}},
          %RegisterApplicationInstance{

test/support/factory.ex

@@ -21,6 +21,7 @@ defmodule Trento.Factory do
   }
 
   alias Trento.Domain.Events.{
+    ApplicationInstanceDeregistered,
     ApplicationInstanceRegistered,
     ClusterDeregistered,
     ClusterRegistered,
@@ -29,6 +30,7 @@ defmodule Trento.Factory do
     DatabaseInstanceDeregistered,
     DatabaseInstanceRegistered,
     DatabaseRegistered,
+    DatabaseRestored,
     HostAddedToCluster,
     HostDetailsUpdated,
     HostRegistered,
@@ -267,6 +269,14 @@ defmodule Trento.Factory do
     })
   end
 
+  def database_restored_event_factory do
+    DatabaseRestored.new!(%{
+      sap_system_id: Faker.UUID.v4(),
+      sid: Faker.UUID.v4(),
+      health: Health.passing()
+    })
+  end
+
   def deregister_database_instance_command_factory do
     DeregisterDatabaseInstance.new!(%{
       sap_system_id: Faker.UUID.v4(),
@@ -298,6 +308,15 @@ defmodule Trento.Factory do
     }
   end
 
+  def application_instance_deregistered_event_factory do
+    ApplicationInstanceDeregistered.new!(%{
+      sap_system_id: Faker.UUID.v4(),
+      deregistered_at: DateTime.utc_now(),
+      instance_number: "00",
+      host_id: Faker.UUID.v4()
+    })
+  end
+
   def deregister_application_instance_command_factory do
     DeregisterApplicationInstance.new!(%{
       sap_system_id: Faker.UUID.v4(),