Add timer.lua

timer.lua

@@ -0,0 +1,69 @@
+local is_callable = function(callback)
+  local _type = type(callback)
+  if _type == "function" then return true end
+  of _type == "table" then
+    local metatable = getmetatable(callback)
+    return (type(metatable) == "table") and (type(metatable.__call) == "function")
+  end
+end
+
+local update_after = function(self, delta)
+  if self.running >= self.time then return true end
+  self.running = self.running + delta
+  if self.running >= self.time then
+    self.callback(unpack(self.args))
+    return true
+  end
+end
+
+local update_every = function(self, delta)
+  self.running = self.running + delta
+  while self.running >= self.time do
+    self.callback(unpack(self.args))
+    self.running = self.running - self.time
+  end
+end
+
+local metatable = {
+  reset = function(self, time)
+    self.running = time or 0
+  end,
+}
+
+local timers = {}
+
+local new_timer = function(time, callback, update, ...)
+  assert(is_callable(callback), "callback function must be callable")
+
+  local timer = setmetatable({
+    time = time,
+    callback = callback,
+    update = update,
+    args = {...},
+    running = 0,
+  }, metatable)
+
+  timers[timer] = timer
+  return timer
+end
+
+return {
+  after = function(time, callback, ...)
+    return new_timer(time, callback, update_after, ...)
+  end,
+  every = function(time, callback, ...)
+    return new_timer(time, callback, update_every, ...)
+  end,
+  update = function(delta)
+    local expired = {}
+    for timer in pairs(timers) do
+      if timer:update(delta) then
+        expired[timer] = true
+      end
+    end
+    for timer in pairs(expired) do
+      timers[timer] = nil
+    end
+    return expired
+  end,
+}