-- Constants

local ITERATIONS    = 8

-- Module

local SPRING    = {}

-- Functions

function SPRING.create(self, mass, force, damping, speed)
    local spring    = {
        Target      = Vector3.new();
        Position    = Vector3.new();
        Velocity    = Vector3.new();

        Mass        = mass or 5;
        Force       = force or 50;
        Damping     = damping or 4;
        Speed       = speed  or 4;
    }

    function spring.shove(self, force)
        local x, y, z   = force.X, force.Y, force.Z
        if x ~= x or x == math.huge or x == -math.huge then
            x   = 0
        end
        if y ~= y or y == math.huge or y == -math.huge then
            y   = 0
        end
        if z ~= z or z == math.huge or z == -math.huge then
            z   = 0
        end
        self.Velocity   = self.Velocity + Vector3.new(x, y, z)
    end

    function spring.update(self, dt)
        local scaledDeltaTime = math.min(dt,1) * self.Speed / ITERATIONS

        for i = 1, ITERATIONS do
            local force         = self.Target - self.Position
            local acceleration  = (force * self.Force) / self.Mass

            acceleration        = acceleration - self.Velocity * self.Damping

            self.Velocity   = self.Velocity + acceleration * scaledDeltaTime
            self.Position   = self.Position + self.Velocity * scaledDeltaTime
        end

        return self.Position
    end

    return spring
end

-- Return

return SPRING