Editing Module:Check for unknown parameters

-- This module may be used to compare the arguments passed to the parent
-- with a list of arguments, returning a specified result if an argument is
-- not on the list
local p = {}

local function trim(s)
	return s:match('^%s*(.-)%s*$')
end

local function isnotempty(s)
	return s and trim(s) ~= ''
end

function p.check (frame)
	local args = frame.args
	local pargs = frame:getParent().args
	local ignoreblank = isnotempty(frame.args['ignoreblank'])
	local checkpos = isnotempty(frame.args['checkpositional'])
	local knownargs = {}
	local unknown = frame.args['unknown'] or 'Found _VALUE_, '
	local preview = frame.args['preview'] or unknown

	local res = {}
	local regexps = {}
	local comments = {}
	local commentstr = ''
	
	local ispreview = frame:preprocess( "{{REVISIONID}}" ) == "" and 1 or 0
	if ispreview then ignoreblank = nil end

	-- create the list of known args, regular expressions, and the return string
	for k, v in pairs(args) do
		if type(k) == 'number' then
			v = trim(v)
			knownargs[v] = 1
		elseif k:find('^regexp[1-9][0-9]*$') then
			table.insert(regexps, '^' .. v .. '$')
		end
	end
	if isnotempty(frame.args['preview']) then 
		preview = '<div class="hatnote" style="color:red"><strong>Warning:</strong> ' .. frame.args['preview'] .. ' (this message is shown only in preview).</div>'
	elseif frame.args['preview'] then
		preview = frame.args['preview']
	else
		preview = unknown
	end
	if ispreview == 1 then unknown = preview end
	
	-- adds one result to the output tables
	local function addresult(k)
		if k == '' then
			-- Fix odd bug for | = which gets stripped to the empty string and
			-- breaks category links
			k = ' '
		end
		local r = unknown:gsub('_VALUE_', k)
		table.insert(res, r)
		table.insert(comments, '"' .. k .. '"')
	end

	-- loop over the parent args, and make sure they are on the list
	for k, v in pairs(pargs) do
		if type(k) == 'string' and knownargs[k] == nil then
			local knownflag = false
			for i, regexp in ipairs(regexps) do
				if mw.ustring.match(k, regexp) then
					knownflag = true
					break
				end
			end
			if not knownflag and ( not ignoreblank or isnotempty(v) )  then
				k = mw.ustring.gsub(k, '[^%w\-_ ]', '?')
				addresult(k)
			end
		elseif checkpos and
			type(k) == 'number' and 
			knownargs[tostring(k)] == nil and
			( not ignoreblank or isnotempty(v) )
		then
			addresult(k)
		end
	end

	if #comments > 0 then
		commentstr = '<!-- Module:Check for unknown parameters results: ' ..
			table.concat(comments, ', ') .. '-->'
	end
	
	return table.concat(res) .. commentstr
end

return p