Help with recreating the Roblox Dragger object.

I'm recreating the dragger object to seamlessly work with code that uses it already, all is well except I can't quite figure out that actual part dragging.

Basically I need to come up with a function that can take a table of parts, an offset point (the point grabbed at), and a new CFrame (that being mouse.hit). How might I do that? Also how would i get parts to stick to the side of other parts instead of popping on top?

My code so far (in a module script):

local Dragger = {
	MainPart = nil,
	GrabPoint = Vector3.new(),
	Parts = {},
	IsDown = false,
	MoveParts = (function(self, Parts, Offset, New)
		-- Here's where i'm stuck
	end),
	MouseDown = (function(self, MousePart, PointOnMousePart, Parts)
		print("Down")
		if self.IsDown == false then
			--set MainPart, GrabPoint, and Parts, Set IsDown to true.
			self.MainPart = MousePart
			self.GrabPoint = PointOnMousePart
			self.Parts = Parts
			self.IsDown = true
		else
			pcall(error("MouseDown is in use, call MouseUp before using again"))
		end
	end),
	MouseMove = (function(self,MouseRay)
		print("Move")
		if self.IsDown == true then
			--Move GrabPoint and Parts relative to GrabPoint
			local NewRay = Ray.new(MouseRay.Origin, MouseRay.Direction * 999)
			local RayPart, RayHit = Workspace:FindPartOnRayWithIgnoreList(NewRay, self.Parts)
			if RayPart then
				print(self.GrabPoint)
				self:MoveParts(self.Parts, CFrame.new(self.GrabPoint), CFrame.new(RayHit))
			end
		else
			error("MouseMoved called without MouseDown")
		end
	end),
	MouseUp = (function(self)
		print("Up")
		--stop the dragging action, clear mainpart, grabpoint, parts, Set IsDown to false.
		if self.IsDown == true then
			self.MainPart = nil
			self.GrabPoint = Vector3.new()
			self.Parts = {}
			self.IsDown = false
		else
			error("MouseUp called before MouseDown")
		end
	end),
	AxisRotate = (function(self, Axis)
		--Rotate on the given axis
		if Axis == 0 or Axis == Enum.Axis.X or (type(Axis) == "string" and Axis:lower() == "x")then
			Axis = CFrame.Angles(90,0,0)
		elseif Axis == 1 or Axis == Enum.Axis.Y or (type(Axis) == "string" and Axis:lower() == "y") then
			Axis = CFrame.Angles(0,90,0)
		elseif Axis == 2 or Axis == Enum.Axis.Z or (type(Axis) == "string" and Axis:lower() == "z") then
			Axis = CFrame.Angles(0,0,90)
		--[[else
			Axis = CFrame.Angles(0,0,0)--]]
		end
		print(Axis)
		self:MoveParts(self.Parts, CFrame.new(self.GrabPoint), CFrame.new(self.GrabPoint) * Axis)
	end)
}

return Dragger

Two things:

**1)**Why did you do a script that check the position of the GrabPoint instead of getting the mouse position?

2)Parts = {}, why? You need to move only 1 part..