feat: Allow creating a budget up to 2 years ahead

app/models/budget.rb

@@ -29,13 +29,14 @@ class Budget < ApplicationRecord
     end
 
     def budget_date_valid?(date, family:)
-      if family.uses_custom_month_start?
-        budget_start = family.custom_month_start_for(date)
-        budget_start >= oldest_valid_budget_date(family) && budget_start <= family.custom_month_end_for(Date.current)
+      budget_start = if family.uses_custom_month_start?
+        family.custom_month_start_for(date)
       else
-        beginning_of_month = date.beginning_of_month
-        beginning_of_month >= oldest_valid_budget_date(family) && beginning_of_month <= Date.current.end_of_month
+        date.beginning_of_month
       end
+
+      budget_start >= oldest_valid_budget_date(family) &&
+        budget_start <= latest_valid_budget_start_date(family)
     end
 
     def find_or_bootstrap(family, start_date:)
@@ -70,6 +71,14 @@ class Budget < ApplicationRecord
         oldest_entry_date = family.oldest_entry_date.beginning_of_month
         [ two_years_ago, oldest_entry_date ].min
       end
+
+      def latest_valid_budget_start_date(family)
+        if family.uses_custom_month_start?
+          family.current_custom_month_period.start_date + 2.years
+        else
+          Date.current.beginning_of_month + 2.years
+        end
+      end
   end
 
   def period
@@ -151,8 +160,6 @@ class Budget < ApplicationRecord
   end
 
   def next_budget_param
-    return nil if current?
-
     next_date = start_date + 1.month
     return nil unless self.class.budget_date_valid?(next_date, family: family)
 

test/models/budget_test.rb

@@ -58,8 +58,35 @@ class BudgetTest < ActiveSupport::TestCase
     refute Budget.budget_date_valid?(3.years.ago.beginning_of_month, family: @family)
   end
 
-  test "budget_date_valid? does not allow future dates beyond current month" do
-    refute Budget.budget_date_valid?(2.months.from_now, family: @family)
+  test "budget_date_valid? allows future dates up to 2 years ahead" do
+    travel_to Date.current.beginning_of_month do
+      assert Budget.budget_date_valid?(Date.current.beginning_of_month + 1.month, family: @family)
+      assert Budget.budget_date_valid?(Date.current.beginning_of_month + 2.years, family: @family)
+    end
+  end
+
+  test "budget_date_valid? does not allow future dates beyond 2 years ahead" do
+    travel_to Date.current.beginning_of_month do
+      refute Budget.budget_date_valid?(Date.current.beginning_of_month + 2.years + 1.month, family: @family)
+    end
+  end
+
+  test "budget_date_valid? for custom month start allows dates up to 2 years ahead" do
+    @family.update!(month_start_day: 15)
+
+    travel_to Date.current.beginning_of_month do
+      cap_start = @family.current_custom_month_period.start_date + 2.years
+      assert Budget.budget_date_valid?(cap_start, family: @family)
+    end
+  end
+
+  test "budget_date_valid? for custom month start does not allow dates beyond 2 years ahead" do
+    @family.update!(month_start_day: 15)
+
+    travel_to Date.current.beginning_of_month do
+      beyond_cap = @family.current_custom_month_period.start_date + 2.years + 1.month
+      refute Budget.budget_date_valid?(beyond_cap, family: @family)
+    end
   end
 
   test "previous_budget_param returns nil when date is too old" do
@@ -75,6 +102,49 @@ class BudgetTest < ActiveSupport::TestCase
     assert_nil budget.previous_budget_param
   end
 
+  test "next_budget_param returns next month when current month budget is selected" do
+    travel_to Date.current.beginning_of_month do
+      budget = Budget.create!(
+        family: @family,
+        start_date: Date.current.beginning_of_month,
+        end_date: Date.current.end_of_month,
+        currency: "USD"
+      )
+
+      assert_equal Budget.date_to_param(Date.current.beginning_of_month + 1.month), budget.next_budget_param
+    end
+  end
+
+  test "next_budget_param returns nil at future cap" do
+    travel_to Date.current.beginning_of_month do
+      cap_start = Date.current.beginning_of_month + 2.years
+      budget = Budget.create!(
+        family: @family,
+        start_date: cap_start,
+        end_date: cap_start.end_of_month,
+        currency: "USD"
+      )
+
+      assert_nil budget.next_budget_param
+    end
+  end
+
+  test "next_budget_param returns nil at future cap for custom month start" do
+    @family.update!(month_start_day: 15)
+
+    travel_to Date.current.beginning_of_month do
+      cap_start = @family.current_custom_month_period.start_date + 2.years
+      budget = Budget.create!(
+        family: @family,
+        start_date: cap_start,
+        end_date: cap_start + 1.month - 1.day,
+        currency: "USD"
+      )
+
+      assert_nil budget.next_budget_param
+    end
+  end
+
   test "actual_spending nets refunds against expenses in same category" do
     family = families(:dylan_family)
     budget = Budget.find_or_bootstrap(family, start_date: Date.current.beginning_of_month)