Template:Fallback

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This template was imported from commons:Template:Fallback without the here unusable documentation.

---

Use localised subpage for the user language with fallback to {{CONTENTLANGUAGE}}

Template parameters[Edit template data]

Parameter		Description	Type	Status
page	1	Template name	Page name	required
lang	2	override user language on localised page Default {{int:Lang}}	String	optional

The above documentation is transcluded from Template:Fallback/doc. (edit | history)
Editors can experiment in this template’s sandbox (create | mirror) and testcases (create) pages.
Please add categories to the /doc subpage. Subpages of this template.

local p = {}

local langlist = require('Module:Fallbacklist')

function p.fblist(lang) -- list the full fallback chain from a language to en
	local fbstr = p.fallbackloop(' ' .. lang) 
	fbstr = fbstr .. ' ' .. 'default'
	fbstr = fbstr .. ' ' .. 'en'
	return mw.text.split(fbstr, " ")
end

function p.fallbackloop(init)  --list of fallback languages in string format (more convenient than tables)
	local new = init
	for i, j in pairs(mw.text.split(init, " ")) do
		if langlist[j] then
			for k, l in pairs(langlist[j]) do
				if not string.find(new, ' ' .. l, 1, true) then
					new = new .. ' ' .. l
				end
			end
		end
	end
	if new ~= init then
		return p.fallbackloop(new)
	end
	return new
end

function p.langSwitch(frame)
	args = mw.getCurrentFrame():getParent().args
	-- Return error if there is not default and no english version
	if not args.en and not args.default and args.nocat ~= '1' then
		return frame:expandTemplate{ title = "red", args = {'LangSwitch error: no default'}} .. '[[Category:LangSwitch template without default version]]' 
	end
	-- get language (either stated one or user's default language)
	local lang = args.lang
	if not lang or lang == '' then
		lang = frame:preprocess( "{{int:lang}}" )
	end
	-- get lhe list of accpetable language (lang + those in lang's fallback chain) and check their content
	local parselist = p.fblist(lang)
	for j, k in pairs(parselist) do 
		if args[k] == '~' then return '' end
		if args[k] and args[k] ~= '' then return args[k] end
	end
end

function p.fallbackpage(base, lang)
	local languages = p.fblist(lang)
	for i, j in pairs(languages) do
		if p.pageexist( base .. '/' .. j) then 
			return base .. '/' .. j 
		end
	end
end

function p.pageexist(page) -- isolated function to deal with old-style #ifexist parser without Lua equivalent 
	local frame = mw.getCurrentFrame()
	local exist = frame:callParserFunction{name = '#ifexist', args= {[1] = page, [2] = "true"} }
	if exist == "true" then return true else return false end
end

function p.autotranslate(frame) -- logic for template:Autotranslate
	local args = mw.getCurrentFrame():getParent().args
	if not args.lang or args.lang == '' then
		args.lang = frame:preprocess( "{{int:lang}}" )
	end
	local page = p.fallbackpage('Template:' .. args.base, args.lang)
	if not page then return "no fallback page found for autotranslate" end
	return frame:expandTemplate{ title = page, args = args }
end

return p