kingdoms_game/mods/utils/scheduler.lua

--[[
Copyright (c) 2014, Robert 'Bobby' Zenz
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--- The Scheduler allows you to easily schedule functions for execution. Under
-- the hood it used minetest.register_on_globalstep to schedule functions.
scheduler = {
	--- If more time has elapsed than the interval of the scheduled function,
	-- the function will be run as many times as necessary to catch up.
	OVERSHOOT_POLICY_CATCH_UP = 1,
	
	--- If more time has elpased than the interval of the scheduled function,
	-- the function will still only be run once.
	OVERSHOOT_POLICY_RUN_ONCE = 2,
	
	--- The table of functions for immediate execution.
	immediate_functions = {},
	
	--- If the scheduler has been initialized.
	initialized = false,
	
	-- The table of scheduled functions.
	scheduled_functions = {}
}


--- Initializes the scheduler.
--
-- Note that the client should never need to call this function.
function scheduler.init()
	if not scheduler.initialized then
		minetest.register_globalstep(scheduler.step)
	end
end

--- Schedules the given function.
--
-- @param name The name of the function.
-- @param interval The interval in which to run the function. A value of zero
--                 will make the function run on every global step,
--                 the overshoot policy will have no effect in that case.
-- @param run_function The function to execute.
-- @param overshoot_policy Optional. The overshoot policy. Defaults to
--                         scheduler.OVERSHOOT_POLICY_RUN_ONCE.
function scheduler.schedule(name, interval, run_function, overshoot_policy)
	scheduler.scheduled_functions[name] = {
		interval = interval,
		overshoot_policy = overshoot_policy or scheduler.OVERSHOOT_POLICY_RUN_ONCE,
		run_function = run_function,
		timer = 0
	}
	
	if not scheduler.initialized then
		scheduler.init()
	end
end

--- The step function that is registered with minetest.register_on_globalstep.
--
-- Note that the client should never call this function as it might mess up
-- the scheduled functions.
--
-- @param since_last_call The elapsed time since the last call.
function scheduler.step(since_last_call)
	for name, scheduled in pairs(scheduler.scheduled_functions) do
		if scheduled.interval > 0 then
			scheduled.timer = scheduled.timer + since_last_call
			
			if scheduled.timer >= scheduled.interval then
				scheduled.run_function()
				
				local additional_runs = math.floor(scheduled.timer / scheduled.interval) - 1
				
				if scheduled.overshoot_policy == scheduler.OVERSHOOT_POLICY_CATCH_UP then
					for counter = 1, additional_runs, 1 do
						scheduled.run_function()
					end
				end
				
				scheduled.timer = 0
			end
		else
			scheduled.run_function()
		end
	end
end

--- Unschedules/Removes the function with the given name.
--
-- @param name The name of the function to unschedule.
function scheduler.unschedule(name)
	scheduler.scheduled_functions[name] = nil
end