refactor: fix review comments

lib/mv/config.ex

@@ -470,11 +470,19 @@ defmodule Mv.Config do
   # ---------------------------------------------------------------------------
 
   @doc """
-  Returns SMTP host. ENV `SMTP_HOST` overrides Settings.
+  Returns SMTP host.
+
+  Policy:
+  - ENV-only mode (`SMTP_HOST` set): read from ENV `SMTP_HOST`
+  - Settings mode: read from Settings only
   """
   @spec smtp_host() :: String.t() | nil
   def smtp_host do
-    smtp_env_or_setting("SMTP_HOST", :smtp_host)
+    if smtp_env_mode?() do
+      System.get_env("SMTP_HOST") |> trim_nil()
+    else
+      get_from_settings(:smtp_host)
+    end
   end
 
   @doc """
@@ -522,7 +530,7 @@ defmodule Mv.Config do
   def smtp_password do
     if smtp_env_mode?() do
       case System.get_env("SMTP_PASSWORD") do
-        nil -> smtp_password_from_file_or_settings()
+        nil -> smtp_password_from_file()
         value -> trim_nil(value)
       end
     else
@@ -530,7 +538,7 @@ defmodule Mv.Config do
     end
   end
 
-  defp smtp_password_from_file_or_settings do
+  defp smtp_password_from_file do
     case System.get_env("SMTP_PASSWORD_FILE") do
       nil -> nil
       path -> read_smtp_password_file(path)
@@ -568,14 +576,6 @@ defmodule Mv.Config do
     present?(smtp_host())
   end
 
-  @doc """
-  Returns true when SMTP ENV mode is active.
-  """
-  @spec smtp_env_configured?() :: boolean()
-  def smtp_env_configured? do
-    smtp_env_mode?()
-  end
-
   @doc """
   Returns true when SMTP is managed by environment variables.
 
@@ -599,6 +599,7 @@ defmodule Mv.Config do
       []
       |> maybe_add_missing("SMTP_USERNAME", smtp_username_env_set?())
       |> maybe_add_missing("SMTP_PASSWORD/SMTP_PASSWORD_FILE", smtp_password_env_set?())
+      |> Enum.reverse()
     else
       []
     end
@@ -665,8 +666,6 @@ defmodule Mv.Config do
   @spec mail_from_email_env_set?() :: boolean()
   def mail_from_email_env_set?, do: env_set?("MAIL_FROM_EMAIL")
 
-  defp parse_smtp_port_env(nil), do: nil
-
   defp parse_smtp_port_env(value) when is_binary(value) do
     case Integer.parse(String.trim(value)) do
       {port, _} when port > 0 -> port
@@ -676,16 +675,8 @@ defmodule Mv.Config do
 
   defp parse_smtp_port_env(_), do: nil
 
-  # Reads a plain string SMTP setting: ENV first, then Settings.
-  defp smtp_env_or_setting(env_key, setting_key) do
-    case System.get_env(env_key) do
-      nil -> get_from_settings(setting_key)
-      value -> trim_nil(value)
-    end
-  end
-
   defp maybe_add_missing(acc, _label, true), do: acc
-  defp maybe_add_missing(acc, label, false), do: acc ++ [label]
+  defp maybe_add_missing(acc, label, false), do: [label | acc]
 
   # Reads an integer setting attribute from Settings.
   defp get_from_settings_integer(key) do