refactor: reduce function nesting depth to fix Credo warnings

Extract nested conditionals into separate helper functions:
- check_amount_change/2 and related helpers in MembershipFeeTypeLive.Form
- check_interval_change/2 and related helpers in MemberLive.Form

This reduces nesting depth from 3 to 2, improving code readability.

lib/mv_web/live/member_live/form.ex

@@ -272,39 +272,7 @@ defmodule MvWeb.MemberLive.Form do
     validated_form = AshPhoenix.Form.validate(socket.assigns.form, member_params)
 
     # Check for interval mismatch if membership_fee_type_id changed
-    socket =
+    socket = check_interval_change(socket, member_params)
-      if Map.has_key?(member_params, "membership_fee_type_id") &&
-           socket.assigns.member &&
-           socket.assigns.member.membership_fee_type do
-        new_fee_type_id = member_params["membership_fee_type_id"]
-
-        if new_fee_type_id != "" &&
-             new_fee_type_id != socket.assigns.member.membership_fee_type_id do
-          new_fee_type = find_fee_type(socket.assigns.available_fee_types, new_fee_type_id)
-
-          if new_fee_type &&
-               new_fee_type.interval != socket.assigns.member.membership_fee_type.interval do
-            assign(
-              socket,
-              :interval_warning,
-              gettext(
-                "Warning: Changing from %{old_interval} to %{new_interval} is not allowed. Please select a membership fee type with the same interval.",
-                old_interval:
-                  MembershipFeeHelpers.format_interval(
-                    socket.assigns.member.membership_fee_type.interval
-                  ),
-                new_interval: MembershipFeeHelpers.format_interval(new_fee_type.interval)
-              )
-            )
-          else
-            assign(socket, :interval_warning, nil)
-          end
-        else
-          assign(socket, :interval_warning, nil)
-        end
-      else
-        socket
-      end
 
     {:noreply, assign(socket, form: validated_form)}
   end
@@ -427,6 +395,53 @@ defmodule MvWeb.MemberLive.Form do
     end
   end
 
+  # Checks if membership fee type interval changed and updates socket assigns
+  defp check_interval_change(socket, member_params) do
+    if Map.has_key?(member_params, "membership_fee_type_id") &&
+         socket.assigns.member &&
+         socket.assigns.member.membership_fee_type do
+      handle_interval_change(socket, member_params["membership_fee_type_id"])
+    else
+      socket
+    end
+  end
+
+  # Handles interval change validation
+  defp handle_interval_change(socket, new_fee_type_id) do
+    if new_fee_type_id != "" &&
+         new_fee_type_id != socket.assigns.member.membership_fee_type_id do
+      validate_interval_match(socket, new_fee_type_id)
+    else
+      assign(socket, :interval_warning, nil)
+    end
+  end
+
+  # Validates that new fee type has same interval as current
+  defp validate_interval_match(socket, new_fee_type_id) do
+    new_fee_type = find_fee_type(socket.assigns.available_fee_types, new_fee_type_id)
+
+    if new_fee_type &&
+         new_fee_type.interval != socket.assigns.member.membership_fee_type.interval do
+      show_interval_warning(socket, new_fee_type)
+    else
+      assign(socket, :interval_warning, nil)
+    end
+  end
+
+  # Shows interval mismatch warning
+  defp show_interval_warning(socket, new_fee_type) do
+    assign(
+      socket,
+      :interval_warning,
+      gettext(
+        "Warning: Changing from %{old_interval} to %{new_interval} is not allowed. Please select a membership fee type with the same interval.",
+        old_interval:
+          MembershipFeeHelpers.format_interval(socket.assigns.member.membership_fee_type.interval),
+        new_interval: MembershipFeeHelpers.format_interval(new_fee_type.interval)
+      )
+    )
+  end
+
   defp find_fee_type(fee_types, fee_type_id) do
     Enum.find(fee_types, &(&1.id == fee_type_id))
   end

lib/mv_web/live/membership_fee_type_live/form.ex

@@ -195,36 +195,7 @@ defmodule MvWeb.MembershipFeeTypeLive.Form do
     validated_form = AshPhoenix.Form.validate(socket.assigns.form, params)
 
     # Check if amount changed on edit
-    socket =
+    socket = check_amount_change(socket, params)
-      if socket.assigns.membership_fee_type && Map.has_key?(params, "amount") do
-        new_amount_str = params["amount"]
-        old_amount = socket.assigns.membership_fee_type.amount
-
-        case Decimal.parse(new_amount_str) do
-          {new_amount, _} when is_struct(new_amount, Decimal) ->
-            if Decimal.compare(new_amount, old_amount) != :eq do
-              # Amount changed - show warning
-              affected_count = get_affected_member_count(socket.assigns.membership_fee_type.id)
-
-              socket
-              |> assign(:show_amount_warning, true)
-              |> assign(:old_amount, old_amount)
-              |> assign(:new_amount, new_amount)
-              |> assign(:affected_member_count, affected_count)
-              |> assign(:pending_amount, new_amount_str)
-            else
-              # Amount unchanged - hide warning
-              socket
-              |> assign(:show_amount_warning, false)
-              |> assign(:pending_amount, nil)
-            end
-
-          :error ->
-            socket
-        end
-      else
-        socket
-      end
 
     {:noreply, assign(socket, form: validated_form)}
   end
@@ -322,6 +293,49 @@ defmodule MvWeb.MembershipFeeTypeLive.Form do
   defp return_path("index", _membership_fee_type), do: ~p"/membership_fee_types"
 
   @spec get_affected_member_count(String.t()) :: non_neg_integer()
+  # Checks if amount changed and updates socket assigns accordingly
+  defp check_amount_change(socket, params) do
+    if socket.assigns.membership_fee_type && Map.has_key?(params, "amount") do
+      handle_amount_change(socket, params["amount"], socket.assigns.membership_fee_type.amount)
+    else
+      socket
+    end
+  end
+
+  # Handles amount change detection and warning assignment
+  defp handle_amount_change(socket, new_amount_str, old_amount) do
+    case Decimal.parse(new_amount_str) do
+      {new_amount, _} when is_struct(new_amount, Decimal) ->
+        if Decimal.compare(new_amount, old_amount) != :eq do
+          show_amount_warning(socket, old_amount, new_amount, new_amount_str)
+        else
+          hide_amount_warning(socket)
+        end
+
+      :error ->
+        socket
+    end
+  end
+
+  # Shows amount change warning with affected member count
+  defp show_amount_warning(socket, old_amount, new_amount, new_amount_str) do
+    affected_count = get_affected_member_count(socket.assigns.membership_fee_type.id)
+
+    socket
+    |> assign(:show_amount_warning, true)
+    |> assign(:old_amount, old_amount)
+    |> assign(:new_amount, new_amount)
+    |> assign(:affected_member_count, affected_count)
+    |> assign(:pending_amount, new_amount_str)
+  end
+
+  # Hides amount change warning
+  defp hide_amount_warning(socket) do
+    socket
+    |> assign(:show_amount_warning, false)
+    |> assign(:pending_amount, nil)
+  end
+
   defp get_affected_member_count(fee_type_id) do
     case Ash.count(Member |> Ash.Query.filter(membership_fee_type_id == ^fee_type_id)) do
       {:ok, count} -> count