local p = {}

-- Credit to http://stackoverflow.com/a/1283608/2644759
-- cc-by-sa 3.0
local function tableMerge(t1, t2, overwrite)
	for k,v in pairs(t2) do
		if type(v) == "table" and type(t1[k]) == "table" then
			-- since type(t1[k]) == type(v) == "table", so t1[k] and v is true
			tableMerge(t1[k], v, overwrite) -- t2[k] == v
		else
			if overwrite or t1[k] == nil then t1[k] = v end
		end
	end
	return t1
end

function p.loadI18n(name, i18n_arg)
	local exist, res = pcall(require, name)
	if exist and next(res) ~= nil then
		if i18n_arg then
			tableMerge(i18n_arg, res.i18n, true)
		elseif type(i18n) == "table" then
			-- merge to global i18n
			tableMerge(i18n, res.i18n, true)
		end
	end
end

function p.loadI18nFrame(frame, i18n_arg)
	p.loadI18n(frame:getTitle().."/i18n", i18n_arg)
end

local function missinginpage(page, lang)
	if type(page) == 'string' then
		page = require(page)
	end
	local list = {}
	for i, j in pairs(page) do
		if i ~= 'keys' and (not j[lang]) and not (j.default) and (not j.message) and (not j.item) then
			table.insert(list, i)
		end
	end
	if #list == 0 then
		return "No translation missing for " .. lang .. '! '
	else
		return #list .. " translations missing in " .. lang .. ':\n* ' .. table.concat(list, '\n* ')
	end
end
function p.pagedoc(frame)
	local page = mw.title.getCurrentTitle().fullText
	page = mw.text.split(page , '/')[1] .. '/' .. mw.text.split(page , '/')[2]
	local lang = frame:preprocess("{{int:lang}}")
	return missinginpage(page, lang)
end

return p