మాడ్యూల్:Fallback

--[[
  __  __           _       _        _____     _ _ _                _
 |  \/  | ___   __| |_   _| | ___ _|  ___|_ _| | | |__   __ _  ___| | __
 | |\/| |/ _ \ / _` | | | | |/ _ (_) |_ / _` | | | '_ \ / _` |/ __| |/ /
 | |  | | (_) | (_| | |_| | |  __/_|  _| (_| | | | |_) | (_| | (__|   < 
 |_|  |_|\___/ \__,_|\__,_|_|\___(_)_|  \__,_|_|_|_.__/ \__,_|\___|_|\_\
 
 Authors and maintainers:
* User:Zolo   - original version
* User:Jarekt 
]]

local p = {}

--[[
translatelua
 
Allows easy translation or internalization of pages in Lua. 
 
Example Usage from a template:
{{#invoke: fallback|translatelua| i18n/oil on canvas|lang={{{lang|}}}}}
 
Parameters:
  frame.args.1 - name of translation module
frame.args.2 - field name of the structure in Module:[frame.args.1] to use
  frame.args.lang - desired language (often user's native language)
 
 Error Handling:
 
]]
function p.translatelua(frame)
	local lang = mw.text.trim(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 lang == '' then
		lang = frame:callParserFunction("int", "lang")
	end
	if frame.args[2] then
		page = page[mw.text.trim(frame.args[2])]
	end
	
	local langList = mw.language.getFallbacksFor(lang)
	table.insert(langList,1,lang)
	for _,language in ipairs(langList) do
		if page[language] then
			return page[language]
		end
	end
end

--[[
fblist
 
Similar to  mw.language.getFallbacksFor(lang) but uses Commons old fallback chain 
 
Parameters:
  lang - desired language (often user's native language)
 
 Error Handling:
 
]]
function p.fblist(lang) -- list the full fallback chain from a language to en
	local fbtable = p.fallbackloop{lang:lower()}
	table.insert(fbtable, 'default')
	table.insert(fbtable, 'en')
	return fbtable
end

local function _inArray(x, t)
	for i, v in ipairs(t) do
		if v == x then return i end
	end
	return -1
end

function p.fallbackloop(fbtable) --list of fallback languages in string format (more convenient than tables)
	local langlist = require('Module:Fallbacklist')
	local changes = false
	for i, j in ipairs(fbtable) do
		local seq = langlist[j]
		if seq then
			for k, l in ipairs(seq) do
				if _inArray(l, fbtable) == -1 then
					table.insert(fbtable, l)
					changes = true
				end
			end
		end
	end
	if changes then
		return p.fallbackloop(fbtable)
	end
	return fbtable
end

return p