#!lua

require "luanet"

-- C#-style using clause:
--	luanet.using(expr, function(var) ... end)
local IDisposable = luanet.System.Type:GetType('System.IDisposable')
local function using_statement(expr,body)
	assert(IDisposable:IsInstanceOfType(expr), "Expected: IDisposable")
	pcall(body, expr)
	expr:Dispose()
end

-- C#-style using directive:
--	luanet.using('System', 'System.IO', 'System.Windows.Forms')
local import_type = luanet.import_type
local load_assembly = luanet.load_assembly
local components
local function using_directive(...)
	local _G = getfenv(3) -- 3:caller() 2:using() 1:using_directive()
	if not getmetatable(_G) then
		local m = {}
		function m:__index(name)
			print("_G",name)
			for i = 1,table.getn(components) do
				local n = components[i] .. "." .. name
				print("try",n)
				load_assembly(n)
				local ty = import_type(n)
				if ty then
					print("found",n)
					rawset(self, name, ty)
					return ty
				end
			end
			return nil
		end
		setmetatable(_G, m)
		components = {}
	end
	for i = 1,table.getn(arg) do
		local c = arg[i]
		if type(c) ~= "string" then
			assert(type(c) == "table", "Expected type name or reference")
			c = rawget(c, '.fqn')
		end
		--load_assembly(c)
		table.insert(components, c)
	end
	return using_directive
end

-- Is this a directive or a clause?
local function using(a,...)
	if type(a)=="string" or type(a)=="table" then
		return using_directive(a, unpack(arg))
	else
		return using_statement(a, unpack(arg))
	end
end
luanet.using = using

return using