# Module:Fallback

local p = {}  
function p.fblist(lang, langonly) -- list the full fallback chain from a language to en
local fbtable = mw.language.getFallbacksFor(lang)
table.insert(fbtable, 1, lang)
if not langonly then
table.insert(fbtable, 'message')
table.insert(fbtable, 'default')
end
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>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 -- version to be used from wikitext
local args = .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 = :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 = :preprocess( "" )
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 -- logic for template:Autotranslate
local args = .args
if not args.lang or args.lang == '' then
args.lang = :preprocess( "" ) -- get user's chosen language
end  
-- find base page
local base = args.base
if not base or base == '' then
return '<strong>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>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 with template arguments the same as the ones passed to template.
return :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
local lang = .args.lang
local page = require('Module:' .. mw.text.trim(.args[1])) -- page should only contain a simple of translations
if not lang or mw.text.trim(lang) == '' then
lang = :preprocess( "" )
end
if .args[2] then
page = page[mw.text.trim(.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
-- list all input arguments of the template that calls ""
local str = ''
for name, value in pairs( :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