diff --git a/Fallback.lua b/Fallback.lua
new file mode 100644
index 0000000..9cb56bd
--- /dev/null
+++ b/Fallback.lua
@@ -0,0 +1,158 @@
+local p = {}
+
+function p.fblist(lang) -- list the full fallback chain from a language to en
+	local fbtable = mw.language.getFallbacksFor(lang)
+	table.insert(fbtable, 1, lang)
+	table.insert(fbtable, 'message')
+	table.insert(fbtable, 'default')
+	return fbtable
+end
+
+function p._langSwitch(args, lang) -- args: table of translations
+	-- Return error if there is not default and no English version
+	-- otherwise returns the message in the most appropriate, plus the lang code as a second value
+	if not args.en and not args.default and not args.message and args.nocat ~= '1' then
+		return error("langSwitch error: no default")
+	end
+	-- get language (either stated one or user's default language)
+	if not lang then
+		return '<strong class="error">LangSwitch Error: no lang</strong>' -- must become proper error
+	end
+	-- get the list of acceptable language (lang + those in lang's fallback chain) and check their content
+	for i, j in ipairs(p.fblist(lang)) do
+		if args[j] then
+			if args[j] == '~' then return nil, j end
+			if j == 'message' then return tostring(mw.message.new(args[j]):inLanguage(lang)) end -- if this is an interface message
+			if args[j] ~= '' then return args[j], j end
+		end
+	end
+	return nil
+end
+
+function p.langSwitch(frame) -- version to be used from wikitext
+	local args = frame.args
+	-- if no expected args provided than check parent template/module args
+	if not args.en and not args.default and not args.nocat then
+		args = frame:getParent().args
+	end
+	local lang
+	if args.lang and args.lang ~= '' then
+		lang = args.lang
+		args.lang = nil
+	else -- get user's chosen language
+		lang = frame:preprocess( "{{int:lang}}" )
+	end
+	local str, language = p._langSwitch(args, lang)
+	return str -- get the first value of the langSwitch, (the text) not the second (the language)
+end
+
+function p.fallbackpage(base, lang, formatting)
+	local languages = p.fblist(lang)
+	for i, lng in ipairs(languages) do
+		if mw.title.new(base .. '/' .. lng).exists then
+			if formatting == 'table' then
+				return {base .. '/' .. lng, lng} -- returns name of the page + name of the language
+			else
+				return base .. '/' .. lng -- returns only the page
+			end
+		end
+	end
+	return base
+end
+
+function p.autotranslate(frame) -- logic for [[template:Autotranslate]]
+	local args = frame.args
+	if not args.lang or args.lang == '' then
+		args.lang = frame:preprocess( "{{int:lang}}" )           -- get user's chosen language
+	end
+
+	-- find base page
+	local base = args.base
+	if not base or base == '' then
+		return '<strong class="error">Base page not provided for autotranslate</strong>'
+	end
+	if string.sub(base, 2, 9) ~= 'emplate:' then
+		base = 'Template:' .. base   -- base provided without 'Template:' part
+	end
+
+	-- find base template language subpage
+	local page = p.fallbackpage(base, args.lang) --
+	if (not page and base ~= args.base) then
+		-- try the original args.base string. This case is only needed if base is not in template namespace
+		page = p.fallbackpage(args.base, args.lang)
+	end
+	if not page then
+		return string.format('<strong class="error">no fallback page found for autotranslate (base=[[%s]], lang=%s)</strong>', args.base, args.lang)
+	end
+
+	-- repack args in a standard table
+	local newargs = {}
+	for field, value in pairs(args) do
+		if field ~= 'base' then
+			newargs[field] = value
+		end
+	end
+
+	-- Transclude {{page |....}} with template arguments the same as the ones passed to {{autotranslate}} template.
+	return frame:expandTemplate{ title = page, args = newargs }
+end
+
+function p.translate(page, key, lang) --translate data stored in a module
+	if type(page) == 'string' then -- if the requested translation table is not yet loaded
+		page = require('Module:' .. page)
+	end
+
+	local val
+	if page[key] then
+		val = page[key]
+	elseif page.keys and page.keys[key] then-- key 'keys" is an index of all keys, including redirects, see [[Module:i18n/datatype]]
+		val = page.keys[key]
+	end
+	if not val then
+		return '<' .. key .. '>'
+	end
+	return p._langSwitch(val, lang)
+end
+
+function p.translatelua(frame)
+	local lang = frame.args.lang
+	local page = require('Module:' .. mw.text.trim(frame.args[1])) -- page should only contain a simple of translations
+	if not lang or mw.text.trim(lang) == '' then
+		lang = frame:preprocess( "{{int:lang}}" )
+	end
+	if frame.args[2] then
+		page = page[mw.text.trim(frame.args[2])]
+	end
+	return p._langSwitch(page, lang)
+end
+
+function p.runTests()
+	local toFallbackTest = require('Module:Fallback/tests/fallbacks')
+	local result = true
+
+	mw.log('Testing fallback chains')
+	for i, t in ipairs(toFallbackTest) do
+		local fbtbl = table.concat(p.fblist(t.initial), ', ')
+		local expected = table.concat(t.expected, ', ')
+		local ret = (fbtbl == expected)
+		mw.log(i, ret and 'passed' or 'FAILED', t.initial, (not ret) and ('FAILED\nis >>' .. fbtbl .. '<<\nbut should be >>' .. expected .. '<<\n') or '')
+		result = result and ret
+	end
+	
+	return result
+end
+
+function p.showTemplateArguments(frame)
+-- list all input arguments of the template that calls "{{#invoke:Fallback|showTemplateArguments}}"
+	local str = ''
+	for name, value in pairs( frame:getParent().args ) do
+		if str == '' then
+			str = string.format('%s=%s', name, value)          -- argument #1
+		else
+			str = string.format('%s, %s=%s', str, name, value) -- the rest
+		end
+	end
+	return str
+end
+
+return p