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

local err_msg = 'No fallback page found for autotranslate (base=[[:%s]], lang=%s)'

-- local function to help normalize input arguments
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 function fallback_list(lang)
	-- get language fallback list
	if not lang or not mw.language.isSupportedLanguage(lang) then
		lang = frame:callParserFunction( "int", "lang" ) -- get user's chosen language 
	end
	local langList = mw.language.getFallbacksFor(lang)
	table.insert(langList,1,lang) -- user's language will be the first one to check
	return langList
end

-------------------------------------------------------------------------
local function verify(base)
    res = ''
	if (mw.title.getCurrentTitle().namespace==10) then
		-- English language is the last fallback language for most languages, if
		-- nothing else there should be at least an english subpage
		local en_exist = mw.title.new(base .. '/en').exists
		assert(en_exist, string.format(err_msg, base, 'en'))
		if (mw.site.siteName=='Wikimedia Commons') then
			res = '\n[[Category:Autotranslated templates|' .. base .. ']]'
		end 
	end
	return res
end

-- initialize object to be returned
local p = {}

--[[
autotranslate
 
This function is the core part of the Autotranslate template. 
 
Usage from a template:
{{#invoke:autotranslate|autotranslate|base=|lang= }}
 
Parameters:
  frame.args.base - base page name
  frame.args.lang - desired language (often user's default 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)
	local langList = fallback_list(args.lang)

	-- single out autotranslate template parameters and exclude them from
	-- parameters passed to language sub-templates
	local base    = args.base
	local lang    = args.lang
	local default = args.default
	args.base     = nil -- blank it
	args.lang     = nil -- blank it 
	args.default  = nil -- blank it 
	assert(base and  #base>0, 'Base page not provided for autotranslate' )

	-- Local function for expanding a template that can be pcall()ed: call the template 
	-- with the same template arguments as the ones passed to {{autotranslate}} template.
	local function expandTemplate(title)
		return frame:expandTemplate{ title = title, args = args }
	end
	
	-- find base template language subpage
	local success, res
	for _, language in ipairs(langList) do
		success, res = pcall(expandTemplate, base .. '/' .. language)
		if success then
			break
		end
	end
	if (not success) then
		assert(default, string.format(err_msg, base, lang)) 
		success, res = pcall(expandTemplate, default)
		assert(success, string.format(err_msg, base, default))
	end

	return res .. verify(base)
end

--------------------------------------------------------------------------------
function p.autotranslate_te(frame) 
	-- version of autotranslate that works with translation extension

	-- 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)
	local langList = fallback_list(args.lang)
	
	-- single out autotranslate template parameters and exclude them from
	-- parameters passed to language sub-templates
	local base    = args.base
	local lang    = args.lang
	local default = args.default
	args.base     = nil -- blank it
	args.lang     = nil -- blank it 
	args.default  = nil -- blank it 
	assert(base and  #base>0, 'Base page not provided for autotranslate' )
	
	-- find base template language subpage
	local page = default  -- default page if provided or nil otherwise
	for _, language in ipairs(langList) do
		if mw.title.new(base .. '/' .. language).exists then
			page =  base .. '/' .. language -- returns only the page
			break
		end
	end
	
	-- last check for errors. This one would be vary rarely used maybe a language which "isSupportedLanguage" but does 
	-- not have any fallback languages, like qqx
	assert(page, string.format(err_msg, base, lang))
 
	-- Transclude {{page |....}} with template arguments the same as the ones passed to {{autotranslate}} template.
	local res = frame:expandTemplate{ title = page, args = args}
	return res .. verify(base)
end

return p