Module:Fallback

Note: This module is used on a lot of pages. In order not to put too much load on the servers, edits should be kept to a bare minimum. Please discuss proposed changes on the talk page first. Editing a module causes all pages that use the module to be re-rendered. If the module is used often, this can put a lot of load on the servers since it fills up the job queue. Keep in mind that templates that are used on file description pages also show up on other wikis.

This Module is used as a part of the larger mechanism to show a template content in the user's interface language or the most appropriate fallback language. It is used in

• Template:LangSwitch
• Template:Autotranslate

and it will be used in

• Template:SuperFallback
• Template:Fallback

It will replace Template:GetFallback and Template:GetFallback2 templates.

Dependencies

• Module:Fallbacklist catalogs fallback chains for each language.

---

local p = {}

local langlist = require('Module:Fallbacklist')

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

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 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

function p._langSwitch(args, lang) -- args: table of translations
	-- 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 '<strong class="error">LangSwitch Error: no default</strong>[[Category:LangSwitch template without default version]]' 
	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 accpetable language (lang + those in lang's fallback chain) and check their content
	local parselist = p.fblist(lang)
	for i, k in ipairs(parselist) do 
		if args[k] == '~' then return '' end
		if args[k] and args[k] ~= '' then return args[k] end
	end
end

function p.langSwitch(frame) -- version to be used from wikitext
	args = frame.args
	-- if no expected args provided than check parent template/module args
	if args.en==nil and args.default==nil and args.nocat==nil then
		args = mw.getCurrentFrame():getParent().args 
	end
	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
	return p._langSwitch(args, lang)
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
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
	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.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( mw.getCurrentFrame():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