local Bone = {}
function Bone.new (data, parent)
	if not data then error("data cannot be nil", 2) end
	
	local self = {
		data = data,
		parent = parent
	}

	function self:updateWorldTransform (flipX, flipY)
		local parent = self.parent
		if parent then
			self.worldX = self.x * parent.m00 + self.y * parent.m01 + parent.worldX
			self.worldY = self.x * parent.m10 + self.y * parent.m11 + parent.worldY
			self.worldScaleX = parent.worldScaleX * self.scaleX
			self.worldScaleY = parent.worldScaleY * self.scaleY
			self.worldRotation = parent.worldRotation + self.rotation
		else
			self.worldX = self.x
			self.worldY = self.y
			self.worldScaleX = self.scaleX
			self.worldScaleY = self.scaleY
			self.worldRotation = self.rotation
		end
		local radians = math.rad(self.worldRotation)
		local cos = math.cos(radians)
		local sin = math.sin(radians)
		self.m00 = cos * self.worldScaleX
		self.m10 = sin * self.worldScaleX
		self.m01 = -sin * self.worldScaleY
		self.m11 = cos * self.worldScaleY
		if flipX then
			self.m00 = -self.m00
			self.m01 = -self.m01
		end
		if flipY then
			self.m10 = -self.m10
			self.m11 = -self.m11
		end
	end

	function self:setToBindPose ()
		local data = self.data
		self.x = data.x
		self.y = data.y
		self.rotation = data.rotation
		self.scaleX = data.scaleX
		self.scaleY = data.scaleY
	end
	
	return self
end
return Bone