# 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