Add support for delay() and eta() in .s() and .then()

Refs #720

huey/api.py

@@ -859,7 +859,15 @@ def call_local(self, *args, **kwargs):
         return self.func(*args, **kwargs)
 
     def s(self, *args, **kwargs):
+        eta = kwargs.pop('eta', None)
+        delay = kwargs.pop('delay', None)
+        if delay is not None and isinstance(delay, datetime.timedelta):
+            delay = delay.total_seconds()
+        if eta is not None or delay is not None:
+            eta = normalize_time(eta, delay, self.huey.utc)
+
         return self.task_class(args, kwargs,
+                               eta=eta,
                                retries=kwargs.pop('retries', None),
                                retry_delay=kwargs.pop('retry_delay', None),
                                priority=kwargs.pop('priority', None),

huey/tests/test_api.py

@@ -126,6 +126,28 @@ def task_a(n):
         self.assertEqual(len(sched), 1)
         self.assertEqual(sched[0], task)
 
+    def test_schedule_s(self):
+        @self.huey.task()
+        def add(a, b):
+            return a + b
+
+        task = add.s((1, 2), delay=10)
+        task = task.then(add, (3,), delay=20)
+        self.huey.execute(task)
+
+        sched = self.huey.scheduled()
+        self.assertEqual(len(sched), 1)
+        self.assertEqual(sched[0], task)
+
+        t10 = datetime.datetime.now() + datetime.timedelta(seconds=10)
+        self.assertFalse(self.huey.ready_to_run(task))
+        self.assertTrue(self.huey.ready_to_run(task, t10))
+
+        t20 = datetime.datetime.now() + datetime.timedelta(seconds=20)
+        oc = task.on_complete
+        self.assertFalse(self.huey.ready_to_run(oc, t10))
+        self.assertTrue(self.huey.ready_to_run(oc, t20))
+
     def test_revoke_task(self):
         state = {}
         @self.huey.task()