Add validation and flash message for invalid date range in Reports

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

test/controllers/reports_controller_test.rb

@@ -92,6 +92,24 @@ class ReportsControllerTest < ActionDispatch::IntegrationTest
     assert_response :ok # Should not crash, uses defaults
   end
 
+  test "index swaps dates when end_date is before start_date" do
+    start_date = Date.current
+    end_date = 1.month.ago.to_date
+    
+    get reports_path(
+      period_type: :custom,
+      start_date: start_date.to_s,
+      end_date: end_date.to_s
+    )
+    
+    assert_response :ok
+    # Should show flash message about invalid date range
+    assert flash[:alert].present?, "Flash alert should be present"
+    assert_match /End date cannot be before start date/, flash[:alert]
+    # Should display the swapped date range
+    assert_select ".text-sm.text-secondary", text: /Showing data from #{Regexp.escape(end_date.strftime("%b %-d, %Y"))} to #{Regexp.escape(start_date.strftime("%b %-d, %Y"))}/
+  end
+
   test "spending patterns returns data when expense transactions exist" do
     # Create expense category
     expense_category = @family.categories.create!(
@@ -185,4 +203,21 @@ class ReportsControllerTest < ActionDispatch::IntegrationTest
     assert_response :ok, "Export should work with session auth. Response: #{@response.body}"
     assert_equal "text/csv", @response.media_type
   end
+
+  test "export transactions swaps dates when end_date is before start_date" do
+    start_date = Date.current
+    end_date = 1.month.ago.to_date
+    
+    get export_transactions_reports_path(
+      format: :csv,
+      period_type: :custom,
+      start_date: start_date.to_s,
+      end_date: end_date.to_s
+    )
+    
+    assert_response :ok
+    assert_equal "text/csv", @response.media_type
+    # Verify the CSV content is generated (should not crash)
+    assert_not_nil @response.body
+  end
 end