extends SchedulerBase
class_name Scheduler

## Base class for the various scheduler implementations in this package as
## This does not include an implementation of [method PeriodicSchedulerBase.schedule_periodic], 
## refer to [PeriodicScheduler].

const UTC_ZERO : float = 0
const DELTA_ZERO : float = 0

## Represents a notion of time for this scheduler. Tasks being
## scheduled on a scheduler will adhere to the time denoted by this
## property.
## [br]
## [b]Returns:[/b]
## [br]
##    The scheduler's current time, as a datetime instance.
func now() -> float:
	return GDRx.basic.default_now()

## Invoke the given action. This is typically called by instances
## of [ScheduledItem].
## [br]
## [b]Args:[/b]
## [br]
##    [code]action[/code] Action to be executed.
## [br]
##    [code]state[/code] [Optional] state to be given to the action function.
## [br][br]
## 
## [b]Returns:[/b]
## [br]
##    The disposable object returned by the action, if any; or a new
##    (no-op) disposable otherwise.
func invoke_action(action : Callable, state = null) -> DisposableBase:
	var ret = action.call(self, state)
	if ret is DisposableBase:
		return ret
	return Disposable.new()