refactor: add fetch functions to Repo module

they work like get functions but always return a tuple {:ok, item} or
{:error, :not_found}

Signed-off-by: Francesco Noacco <francesco.noacco@secomind.com>

backend/lib/edgehog/astarte.ex

@@ -248,10 +248,7 @@ defmodule Edgehog.Astarte do
 
   """
   def fetch_realm_by_name(realm_name) do
-    case Repo.get_by(Realm, name: realm_name) do
-      %Realm{} = realm -> {:ok, realm}
-      nil -> {:error, :realm_not_found}
-    end
+    Repo.fetch_by(Realm, [name: realm_name], empty_return: :realm_not_found)
   end
 
   @doc """
@@ -399,10 +396,9 @@ defmodule Edgehog.Astarte do
 
   """
   def fetch_realm_device(%Realm{id: realm_id}, device_id) do
-    case Repo.get_by(Device, realm_id: realm_id, device_id: device_id) do
-      %Device{} = device -> {:ok, device}
-      nil -> {:error, :device_not_found}
-    end
+    Repo.fetch_by(Device, [realm_id: realm_id, device_id: device_id],
+      empty_return: :device_not_found
+    )
   end
 
   @doc """

backend/lib/edgehog/base_images.ex

@@ -77,12 +77,8 @@ defmodule Edgehog.BaseImages do
 
   """
   def fetch_base_image_collection(id) do
-    case Repo.get(BaseImageCollection, id) do
-      %BaseImageCollection{} = base_image_collection ->
-        {:ok, preload_defaults_for_base_image_collection(base_image_collection)}
-
-      nil ->
-        {:error, :not_found}
+    with {:ok, base_image_collection} <- Repo.fetch(BaseImageCollection, id) do
+      {:ok, preload_defaults_for_base_image_collection(base_image_collection)}
     end
   end
 
@@ -214,9 +210,8 @@ defmodule Edgehog.BaseImages do
 
   """
   def fetch_base_image(id) do
-    case Repo.get(BaseImage, id) do
-      nil -> {:error, :not_found}
-      %BaseImage{} = base_image -> {:ok, preload_defaults_for_base_image(base_image)}
+    with {:ok, base_image} <- Repo.fetch(BaseImage, id) do
+      {:ok, preload_defaults_for_base_image(base_image)}
     end
   end
 

backend/lib/edgehog/devices.ex

@@ -309,12 +309,8 @@ defmodule Edgehog.Devices do
 
   """
   def fetch_hardware_type(id) do
-    case Repo.get(HardwareType, id) do
-      %HardwareType{} = hardware_type ->
-        {:ok, Repo.preload(hardware_type, :part_numbers)}
-
-      nil ->
-        {:error, :not_found}
+    with {:ok, hardware_type} <- Repo.fetch(HardwareType, id) do
+      {:ok, Repo.preload(hardware_type, :part_numbers)}
     end
   end
 
@@ -483,12 +479,8 @@ defmodule Edgehog.Devices do
 
   """
   def fetch_system_model(id) do
-    case Repo.get(SystemModel, id) do
-      %SystemModel{} = system ->
-        {:ok, Repo.preload(system, [:part_numbers, :hardware_type])}
-
-      nil ->
-        {:error, :not_found}
+    with {:ok, system} <- Repo.fetch(SystemModel, id) do
+      {:ok, Repo.preload(system, [:part_numbers, :hardware_type])}
     end
   end
 

backend/lib/edgehog/groups.ex

@@ -109,10 +109,7 @@ defmodule Edgehog.Groups do
 
   """
   def fetch_device_group(id) do
-    case Repo.get(DeviceGroup, id) do
-      %DeviceGroup{} = device_group -> {:ok, device_group}
-      nil -> {:error, :not_found}
-    end
+    Repo.fetch(DeviceGroup, id)
   end
 
   @doc """

backend/lib/edgehog/repo.ex

@@ -35,6 +35,24 @@ defmodule Edgehog.Repo do
     Process.get(@tenant_key)
   end
 
+  def fetch(queryable, id, opts \\ []) do
+    empty = Keyword.get(opts, :empty_return, :not_found)
+
+    case get(queryable, id, opts) do
+      nil -> {:error, empty}
+      item -> {:ok, item}
+    end
+  end
+
+  def fetch_by(queryable, clauses, opts \\ []) do
+    empty = Keyword.get(opts, :empty_return, :not_found)
+
+    case get_by(queryable, clauses, opts) do
+      nil -> {:error, empty}
+      item -> {:ok, item}
+    end
+  end
+
   @impl true
   def prepare_query(_operation, query, opts) do
     cond do

backend/lib/edgehog/tenants.ex

@@ -72,10 +72,7 @@ defmodule Edgehog.Tenants do
 
   """
   def fetch_tenant_by_slug(slug) do
-    case Repo.get_by(Tenant, [slug: slug], skip_tenant_id: true) do
-      %Tenant{} = tenant -> {:ok, tenant}
-      nil -> {:error, :not_found}
-    end
+    Repo.fetch_by(Tenant, [slug: slug], skip_tenant_id: true)
   end
 
   @doc """

backend/lib/edgehog/update_campaigns.ex

@@ -69,12 +69,8 @@ defmodule Edgehog.UpdateCampaigns do
 
   """
   def fetch_update_channel(id) do
-    case Repo.get(UpdateChannel, id) do
-      nil ->
-        {:error, :not_found}
-
-      %UpdateChannel{} = update_channel ->
-        {:ok, preload_defaults_for_update_channel(update_channel)}
+    with {:ok, update_channel} <- Repo.fetch(UpdateChannel, id) do
+      {:ok, preload_defaults_for_update_channel(update_channel)}
     end
   end
 
@@ -368,12 +364,8 @@ defmodule Edgehog.UpdateCampaigns do
 
   """
   def fetch_update_campaign(id) do
-    case Repo.get(UpdateCampaign, id) do
-      nil ->
-        {:error, :not_found}
-
-      %UpdateCampaign{} = update_campaign ->
-        {:ok, preload_defaults_for_update_campaign(update_campaign)}
+    with {:ok, update_campaign} <- Repo.fetch(UpdateCampaign, id) do
+      {:ok, preload_defaults_for_update_campaign(update_campaign)}
     end
   end
 
@@ -492,12 +484,8 @@ defmodule Edgehog.UpdateCampaigns do
 
   """
   def fetch_target(id) do
-    case Repo.get(Target, id) do
-      nil ->
-        {:error, :not_found}
-
-      %Target{} = target ->
-        {:ok, preload_defaults_for_target(target)}
+    with {:ok, target} <- Repo.fetch(Target, id) do
+      {:ok, preload_defaults_for_target(target)}
     end
   end
 end