local LIBSTUB_MAJOR, LIBSTUB_MINOR = "LibStub", 2
local LibStub = _G[LIBSTUB_MAJOR]

if not LibStub or LibStub.minor < LIBSTUB_MINOR then
	LibStub = LibStub or {libs = { }, minors = { }}
	_G[LIBSTUB_MAJOR] = LibStub
	LibStub.minor = LIBSTUB_MINOR
	function LibStub:NewLibrary(major, minor)
		assert(type(major) == "string", "Bad argument #2 to `NewLibrary' (string expected)")
		minor = assert(tonumber(strmatch(minor, "%d+")), "Minor version must either be a number or contain a number.")
		
		local oldminor = self.minors[major]
		if oldminor and oldminor >= minor then return nil end
		self.minors[major], self.libs[major] = minor, self.libs[major] or { }
		return self.libs[major], oldminor
	end
	function LibStub:GetLibrary(major, silent)
		if not self.libs[major] and not silent then
			error(("Cannot find a library instance of %q."):format(tostring(major)), 2)
		end
		return self.libs[major], self.minors[major]
	end
	function LibStub:IterateLibraries() return pairs(self.libs) end
	setmetatable(LibStub, {__call = LibStub.GetLibrary })
end