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88 lines
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Lua

local util = require "rx.util"
local Subscription = require "rx.subscription"
--- @class CooperativeScheduler
-- @description Manages Observables using coroutines and a virtual clock that must be updated
-- manually.
local CooperativeScheduler = {}
CooperativeScheduler.__index = CooperativeScheduler
CooperativeScheduler.__tostring = util.constant("CooperativeScheduler")
--- Creates a new CooperativeScheduler.
-- @arg {number=0} currentTime - A time to start the scheduler at.
-- @returns {CooperativeScheduler}
function CooperativeScheduler.create(currentTime)
local self = {
tasks = {},
currentTime = currentTime or 0,
}
return setmetatable(self, CooperativeScheduler)
end
--- Schedules a function to be run after an optional delay. Returns a subscription that will stop
-- the action from running.
-- @arg {function} action - The function to execute. Will be converted into a coroutine. The
-- coroutine may yield execution back to the scheduler with an optional
-- number, which will put it to sleep for a time period.
-- @arg {number=0} delay - Delay execution of the action by a virtual time period.
-- @returns {Subscription}
function CooperativeScheduler:schedule(action, delay)
local task = {
thread = coroutine.create(action),
due = self.currentTime + (delay or 0),
}
table.insert(self.tasks, task)
return Subscription.create(function()
return self:unschedule(task)
end)
end
function CooperativeScheduler:unschedule(task)
for i = 1, #self.tasks do
if self.tasks[i] == task then
table.remove(self.tasks, i)
end
end
end
--- Triggers an update of the CooperativeScheduler. The clock will be advanced and the scheduler
-- will run any coroutines that are due to be run.
-- @arg {number=0} delta - An amount of time to advance the clock by. It is common to pass in the
-- time in seconds or milliseconds elapsed since this function was last
-- called.
function CooperativeScheduler:update(delta)
self.currentTime = self.currentTime + (delta or 0)
local i = 1
while i <= #self.tasks do
local task = self.tasks[i]
if self.currentTime >= task.due then
local success, delay = coroutine.resume(task.thread)
if coroutine.status(task.thread) == "dead" then
table.remove(self.tasks, i)
else
task.due = math.max(task.due + (delay or 0), self.currentTime)
i = i + 1
end
if not success then
error(delay)
end
else
i = i + 1
end
end
end
--- Returns whether or not the CooperativeScheduler's queue is empty.
function CooperativeScheduler:isEmpty()
return not next(self.tasks)
end
return CooperativeScheduler