Fast fail on impossible year scenarios (#51)

* Refactor search_and_correct_date call to case on the whole response

* Make search_and_correct_date fast-fail on impossible year scenarios

* Add checks on integer-ness of target years to only match on literal years

lib/crontab/scheduler.ex

@@ -280,16 +280,39 @@ defmodule Crontab.Scheduler do
   end
 
   defp get_run_date(conditions, date, max_runs, direction) do
-    {status, corrected_date} = search_and_correct_date(conditions, date, direction)
+    case search_and_correct_date(conditions, date, direction) do
+      {:found, corrected_date} ->
+        {:ok, corrected_date}
 
-    case status do
-      :found -> {:ok, corrected_date}
-      _ -> get_run_date(conditions, corrected_date, max_runs - 1, direction)
+      {:error, :impossible} ->
+        {:error, "No compliant date was found for your interval."}
+
+      {:not_found, corrected_date} ->
+        get_run_date(conditions, corrected_date, max_runs - 1, direction)
     end
   end
 
   @spec search_and_correct_date(CronExpression.condition_list(), NaiveDateTime.t(), direction) ::
           NaiveDateTime.t() | {:not_found, NaiveDateTime.t()}
+
+  defp search_and_correct_date(
+         [{:year, [target_year]} | _],
+         %NaiveDateTime{year: from_year},
+         :increment
+       )
+       when is_integer(target_year) and target_year < from_year do
+    {:error, :impossible}
+  end
+
+  defp search_and_correct_date(
+         [{:year, [target_year]} | _],
+         %NaiveDateTime{year: from_year},
+         :decrement
+       )
+       when is_integer(target_year) and target_year > from_year do
+    {:error, :impossible}
+  end
+
   defp search_and_correct_date([{interval, conditions} | tail], date, direction) do
     if matches_date?(interval, conditions, date) do
       search_and_correct_date(tail, date, direction)