From 3e6e481a0ff42ca2b1810d8592555dc2e0d5e356 Mon Sep 17 00:00:00 2001
From: novirium <t.wilson.au@gmail.com>
Date: Tue, 24 Mar 2020 15:44:51 +0800
Subject: [PATCH] First pass at task system

---
 shepherd/agent/tasks.py | 118 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 shepherd/agent/tasks.py

diff --git a/shepherd/agent/tasks.py b/shepherd/agent/tasks.py
new file mode 100644
index 0000000..b447592
--- /dev/null
+++ b/shepherd/agent/tasks.py
@@ -0,0 +1,118 @@
+
+from abc import ABC, abstractmethod
+
+from dateutil import tz
+import pytz
+
+from apscheduler.triggers.cron import CronTrigger as APCronTrigger
+
+from configspec import *
+import preserve
+
+
+class TaskTrigger(ABC):
+    """Abstract trigger class"""
+    @abstractmethod
+    def next_time(self, base_time):
+        """
+        Return a time indicating the next trigger time after base_time. Return None if no more
+        trigger events.
+        """
+
+
+@preserve.preservable(exclude_attrs=['ap_trigger'])
+class CronTrigger(TaskTrigger):
+    """
+    Interprets Cron strings using a wrapper around the APScheduler CronTrigger (and so function
+    is similar). Values left as default or supplied as None are set to a wildcard, unless it is
+    a smaller unit than those supplied - where it instead gets set to it's minimum (so setting
+    `hour` to 3 will set `minute` and `second` to 0).
+
+    The trigger format will be matched against
+    The timezone used is always the local system timezone.
+
+    Details available at https://apscheduler.readthedocs.io/en/latest/modules/triggers/cron.html
+    """
+
+    def __init__(self, month=None, day=None, day_of_week=None, hour=None,
+                 minute=None, second=None):
+        self.month = month
+        self.day = day
+        self.day_of_week = day_of_week
+        self.hour = hour
+        self.minute = minute
+        self.second = second
+        self.__restore_init__()
+
+    def __restore_init__(self):
+        # Default timezone is the one from tzlocal
+        self.ap_trigger = APCronTrigger(month=self.month, day=self.day,
+                                        day_of_week=self.day_of_week,
+                                        hour=self.hour, minute=self.minute,
+                                        second=self.second)
+
+    def next_time(self, base_time):
+        """
+        Return a time indicating the next trigger time after base_time. Return None if no more
+        trigger events.
+        """
+        # Convert base_time to UTC with dateutil, then to pytz which APScheduler requires.
+        utc_base_time = base_time.astimezone(tz.tzutc()).astimezone(pytz.utc)
+        fire_time = self.ap_trigger.get_next_fire_time(None, utc_base_time)
+        # Convert back to UTC, as ap_trigger returns a value with local timezone
+        # Use DateUtil, as it doesn't add other crap to tzinfo
+        return fire_time.astimezone(pytz.utc).astimezone(tz.tzutc())
+
+
+TriggerSpec = ConfigSpecification()
+TriggerSpec.add_specs({
+    'month': StringSpec(helptext="Month in year, 1-12"),
+    'day': StringSpec(helptext="Day of month, 1-32"),
+    'day_of_week': StringSpec(helptext="Day of week, 0-6 or mon,tue,wed,thu,fri,sat,sun"),
+    'hour': StringSpec(helptext="Hour in day, 0-23"),
+    'minute': StringSpec(helptext="Minute in hour, 0-59"),
+    'second': StringSpec(helptext="Second in minute, 0-59"),
+}, optional=True)
+
+
+# class IntervalTrigger(TaskTrigger):
+"""
+    Triggers every x period starting from when it was first created (carries over lowpower)
+    """
+#    pass
+
+
+# class SingleTrigger(TaskTrigger):
+"""
+    Either pass a whole datetime instance, or a delta like a period that gets added to current.
+    """
+#    pass
+
+
+class Task():
+    def __init__(self, trigger, interface_call):
+        pass
+        # InterfaceCall already handles the callables and args for us, we just need to preserve
+        # them. Trigger is going to be multiple formats, but the most common will be Cron style.
+
+
+def init_tasks(core_config, applied_config, interface_functions):
+    pass
+    # Check if we have a session to load
+    # Load the session - this includes resolving interfacecalls
+
+    # Return a list of tasks
+
+
+def start_tasks(task_list):
+    pass
+    # Start our scheduler thread to fire off tasks, including the initial grace period checks
+    # Due to our task constraints, our scheduler can be somewhat simplified. We know that task
+    # triggers won't change after init, and they will be infrequent enough that we can just
+    # make a new thread for each task.
+
+    # Maybe have "cycles", where we determine what task is going to occur next, and when.
+    # A main dispatch loop then pretty much delays until that point, or triggers the low power
+    # stuff somehow.
+
+    # Does the low power stuff occur here? Or somewhere else?