Oscillator.lua

local Oscillator = {}
Oscillator.__index = Oscillator

function Oscillator.new(period)
    assert(period > 0)
    return setmetatable({
        period = period or 1,
        time = 0
    }, Oscillator)
end

function Oscillator:update(dt)
    if self.time + dt < self.period then
        self.time = self.time + dt
    else
        self.time = self.time + dt - self.period
    end
end

function Oscillator:reset()
    self.time = 0
end

function Oscillator:get()
    return self.time
end

function Oscillator:getFraction()
    return self.time / self.period
end

function Oscillator:getSin()
    return math.sin(self:getFraction() * math.pi * 2)
end

function Oscillator:getCos()
    return math.cos(self:getFraction() * math.pi * 2)
end

return setmetatable(Oscillator,
    { __call = function(_, ...) return Oscillator.new(...) end })