Module:Fallback

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This documentation is transcluded from Module:Fallback/doc.

This module is rated as ready for general use. It has reached a mature form and is thought to be bug-free and ready for use wherever appropriate. To reduce server load and bad output, it should be improved by sandbox testing rather than repeated trial-and-error editing.

This module is subject to page protection. It is a highly visible module in use by a very large number of pages, or is substituted very frequently. Because vandalism or mistakes would affect many pages, and even trivial editing might cause substantial load on the servers, it is protected from editing.

Dependencies

• Module:Fallbacklist catalogs old fallback chains for each language as it was set up on Commons a decade ago. Lua allows now to access the default MediaWiki fallback chains which are used by most templates.

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

local function normalize_input_args(input_args, output_args)
	for name, value in pairs(input_args) do
		if value ~= '' then -- nuke empty strings
			if type(name) == 'string' then name = string.lower(name) end -- convert to lower case
			output_args[name] = value
		end
	end
	return output_args
end

local p = {}

--[[
_langSwitch
 
This function is the core part of the LangSwitch template. 
 
Example usage from Lua:
text = _langSwitch({en='text in english', pl='tekst po polsku'}, lang)
 
Parameters:
  args - table with translations by language
  lang - desired language (often user's native language)
 
 Error Handling:
 
]]

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 then
		local err = '<strong class="error">LangSwitch Error: no default</strong>'
		if args.nocat ~= '1' then
			err = err..'[[Category:LangSwitch template without default version]]'
			return err
		end
	end
	-- get the list of accepetable language (lang + those in lang's fallback chain) and check their content
	assert(lang, 'LangSwitch Error: no lang')
	local langList = mw.language.getFallbacksFor(lang)
	table.insert(langList, 1, lang)
	table.insert(langList, math.max(#langList, 2), 'default')
	for _, language in ipairs(langList) do
		if args[language] == '~' then
			return ''
		elseif args[language] and args[language] ~= '' then
			return args[language]
		end
	end
end
	
--[[
langSwitch
 
This function is the core part of the LangSwitch template. 
 
Example Usage from a template:
{{#invoke:fallback|langSwitch|en=text in english|pl=tekst po polsku|lang={{int:lang}} }}
 
Parameters:
  frame.args - table with translations by language
  frame.args.lang - desired language (often user's native language)
 
 Error Handling:
 
]]
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
	local lang = args.lang
	if not lang or not mw.language.isSupportedLanguage(lang) then
		lang = frame:callParserFunction("int", "lang") -- get user's chosen language
	end
	args.lang = nil
	return p._langSwitch(args, lang)
end

--[[
autotranslate
 
This function is the core part of the Autotranslate template. 
 
Usage from a template:
{{#invoke:fallback|autotranslate|base=|lang= }}
 
Parameters:
  frame.args.base - base page name
  frame.args.lang - desired language (often user's native language)
 
 Error Handling:
 
]]
function p.autotranslate(frame)
	
	-- switch to lowercase parameters to make them case independent
	local args = {}
	args = normalize_input_args(frame:getParent().args, args)
	args = normalize_input_args(frame.args, args)
	
	-- get language fallback list
	if not args.lang or not mw.language.isSupportedLanguage(args.lang) then
		args.lang = frame:callParserFunction("int", "lang") -- get user's chosen language
	end
	local langList = mw.language.getFallbacksFor(args.lang)
	table.insert(langList, 1, args.lang)
	
	-- find base page
	local base = args.base
	args.base = nil
	assert(base and #base > 0, 'Base page not provided for autotranslate')
	if not mw.ustring.find(base, ':') then -- if base page does not indicate namespace
		base = 'Template:' .. base -- than assume it is a template
	end
	
	-- find base template language subpage
	local page = nil
	for _, language in ipairs(langList) do
		if mw.title.new(base .. '/' .. language).exists then
			page = base .. '/' .. language -- returns only the page
			break
		end
	end
	assert(page, string.format('No fallback page found for autotranslate (base=[[%s]], lang=%s)', base, args.lang))
	
	-- Transclude {{page |....}} with template arguments the same as the ones passed to {{autotranslate}} template.
	return frame:expandTemplate{title = page, args = args}
end

--[[
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 = 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:callParserFunction("int", "lang")
	end
	if frame.args[2] then
		page = page[mw.text.trim(frame.args[2])]
	end
	return p._langSwitch(page, lang)
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