local gettime = require "socket".gettime;

local setmetatable = setmetatable;

local floor = math.floor;

module "throttle"

local throttle = {};

local throttle_mt = { __index = throttle };

function throttle:update()

	local newt = gettime();

	local elapsed = newt - self.t;

	self.t = newt;

	local balance = floor(self.rate * elapsed) + self.balance;

	if balance > self.max then

		self.balance = self.max;

	else

		self.balance = balance;

	end

	return self.balance;

end

function throttle:peek(cost)

	cost = cost or 1;

	return self.balance >= cost or self:update() >= cost;

end

function throttle:poll(cost, split)

	if self:peek(cost) then

		self.balance = self.balance - cost;

		return true;

	else

		local balance = self.balance;

		if split then

			self.balance = 0;

		end

		return false, balance, (cost-balance);

	end

end

function create(max, period)

	return setmetatable({ rate = max / period, max = max, t = 0, balance = max }, throttle_mt);

end

return _M;