Lua Timer

timer.lua

local Timer = {}
Timer.__index = Timer

local RunService = game:GetService("RunService")

function Timer.new()
    local self = setmetatable({}, Timer)

    -- Events
    self._finishedEvent = Instance.new("BindableEvent")
    self.Finished = self._finishedEvent.Event

    self._countdownEvent = Instance.new("BindableEvent")
    self.Countdown = self._countdownEvent.Event

    -- Properties
    self._running = false
    self._duration = nil
    self._time = nil

    return self
end

function Timer:Start(duration)
    if not self._running then
        local timerThread =
            coroutine.wrap(
            function()
                self._running = true
                self._duration = duration
                self._time = tick()

                local prevNum = 0

                while self._running and tick() - self._time < duration do
                    RunService.Heartbeat:Wait()

                    local rounded = 0

                    if self._running then
                        rounded = math.round(self:GetTimeLeft())
                    end

                    if rounded >= 0 and prevNum ~= rounded then
                        self._countdownEvent:Fire(rounded)
                        prevNum = rounded
                    end
                end

                self._running = false
                self._time = nil
                self._duration = nil

                self._finishedEvent:Fire()
            end
        )

        timerThread()
    else
        warn("Timer is already running!")
    end
end

function Timer:Restart(duration)
    self:Stop()
    self:Start(duration)
end

function Timer:GetTimeLeft()
    if self._running then
        local now = tick()
        local timeLeft = self._time + self._duration - now

        if timeLeft <= 0 then
            timeLeft = 0
        end

        return timeLeft
    else
        warn("Timer is not running. You must use timer:Start()")
    end
end

function Timer:IsRunning()
    return self._running
end

function Timer:Stop()
    self._running = false
end

return Timer