h1. cron.lua

@cron.lua@ are a set of functions for executing actions at a certain time interval.

h1. Examples of use

* @cron.after(time, callback)@ will execute callback after the given amount of time units. Returns an identifier (@id@)
* @cron.every(time, callback)@ will repeat the same action periodically. Returns an identifier (@id@)
* @cron.cancel(id)@ will stop a timed action from happening, and will interrupt the periodical execution of a periodic action.
* @cron.reset()@ removes all timed and periodic actions, and resets the time passed back to 0.
* @cron.update(dt)@ is needed to be executed on the main program loop. @dt@ is the amount of time that has passed since the last iteration. When @cron.update@ is executed, cron will check the list of pending actions and execute them if needed.
* @cron.tagged(tag1, tag2, tag3 ...)@ filters other cron methods (@cron.after@, @cron.every@, @cron.update@ & @cron.cancel@ but not @cron.reset@) so that they create clocks with specific tags/ act on clocks with specific tags.

<pre>
local cron = require 'cron'

local function printMessage()
  print('Hello')
end

-- the following calls are equivalent:
cron.after(5, printMessage)
cron.after(5, print, 'Hello')

cron.update(5) -- will print 'Hello' twice

-- this will print the message periodically:
local id = cron.every(10, printMessage)

cron.update(5) -- nothing
cron.update(4) -- nothing
cron.update(12) -- prints 'Hello' twice

cron.cancel(id) -- stops the execution the element defined by id. Works with periodical or one-time actions.

cron.reset() -- stops all the current actions, both timed ones and periodical ones.
</pre>

Some tag examples:
<pre>
  -- This has the same effect of cron.after(2, showMenu), except that the
  -- time entry is tagged with the tags 'main-menu' and 'menu'
  cron.tagged('main-menu', 'menu').after(2, showMenu)

  -- This updates the time entries tagged with the tag 'menu', but not the rest
  cron.tagged('menu').update(2)

  -- cron.cancel does not admit filtering via tags, but it admits tags as params
  -- the previous call is equivalent to this one:
  cron.tagged('main-menu').cancel()
</pre>


h1. Gotchas / Warnings

* @cron.lua@ does *not* implement any hardware or software clock; you will have to provide it with the access to the hardware timers, in the form of periodic calls to @cron.update@
* @cron@ does not have any defined time units (seconds, milliseconds, etc). You define the units it uses by passing it a @dt@ on @cron.update@. If @dt@ is in seconds, then @cron@ will work in seconds. If @dt@ is in milliseconds, then @cron@ will work in milliseconds.

h1. Installation

Just copy the cron.lua file somewhere in your projects (maybe inside a /lib/ folder) and require it accordingly.

Remember to store the value returned by require somewhere! (I suggest a local variable named @cron@)

<pre>
local cron = require 'cron'
</pre>

Also, make sure to read the license file; the text of that license file must appear somewhere in your projects' files.

h1. Specs

This project uses "telescope":https://github.com/norman/telescope for its specs. If you want to run the specs, you will have to install telescope first. Then run:

<pre>
tsc spec/*
</pre>


