Module:Redirect hatnote

 --[[
 -- This module produces a "redirect" hatnote. It looks like this:
 -- '"X" redirects here. For other uses, see Y.'
 -- It implements the {{redirect}} template.
 --]]

 local mHatnote = require('Module:Hatnote')
 local mHatList = require('Module:Hatnote list')
 local mArguments --lazily initialize
 local libraryUtil = require('libraryUtil')
 local checkType = libraryUtil.checkType
 local checkTypeMulti = libraryUtil.checkTypeMulti

 local p = {}

 --------------------------------------------------------------------------------
 -- Helper functions
 --------------------------------------------------------------------------------

 local function getTitle(...)
	--Calls mw.title.new and returns either a title object, or nil on error
	local success, titleObj = pcall(mw.title.new, ...)
	return success and titleObj or nil
 end

 --------------------------------------------------------------------------------
 -- Main functions
 --------------------------------------------------------------------------------

 function p.redirect(frame)
	mArguments = require('Module:Arguments')
	local args = mArguments.getArgs(frame, {parentOnly=true})
	--Get number of redirects
	local numRedirects = tonumber(frame.args[1]) or 1
	-- Create the options table.
	local options = {}
	options.selfref = args.selfref
	return p._redirect(args, numRedirects, options)
 end

 function p._redirect(args, numRedirects, options, currentTitle, redirectTitle, targetTitle)
	-- Validate the input. Don't bother checking currentTitle, redirectTitle or
	-- targetTitle, as they are only used in testing.
	checkType('_redirect', 1, args, 'table')
	checkType('_redirect', 2, numRedirects, 'number', true)
	numRedirects = numRedirects or 1
	checkType('_redirect', 3, options, 'table', true)
	options = options or {}
	currentTitle = currentTitle or mw.title.getCurrentTitle()
	-- Get the table of redirects
	local redirect = {}
	for i = 1, numRedirects do
		-- Return an error if a redirect parameter is missing.
		if not args[i] then
			return mHatnote.makeWikitextError(
				'missing redirect parameter',
				'Template:Redirect#Errors',
				args.category
			)
		end
		redirect[i] = args[i]
	end
	-- Generate the text.
	local formattedRedirect = {}
	for k,v in pairs(redirect) do
		formattedRedirect[k] = mHatnote.quote(v)
	end
	local text = {
		mHatList.andList(formattedRedirect) .. ' ' .. (#redirect == 1 and 'redirects' or 'redirect') .. ' here.',
		mHatList._forSee(args, #redirect + 1, {title = redirect[1], extratext = args.text})
	}
	text = table.concat(text, ' ')
	-- Functionality for adding categories	
	local categoryTable = {}
	local function addCategory(cat)
		if cat and cat ~= '' then
			-- Add by index to avoid duplicates
			categoryTable[string.format('[[Category:%s]]', cat)] = true
		end
	end
	--Generate tracking categories
	local mhOptions = {}
	local redirTitle
	for k,v in pairs(redirect) do
		-- We don't need a tracking category if the template invocation has been
		-- copied directly from the docs, or if we aren't in main- or category-space.
		if not v:find('^REDIRECT%d*$') and v ~= 'TERM' -- 
			and currentTitle.namespace == 0 or currentTitle.namespace == 14
		then
			redirTitle = redirectTitle or getTitle(v)
			if not redirTitle or not redirTitle.exists then
				addCategory('Missing redirects')
			elseif not redirTitle.isRedirect then
				if string.find(redirTitle:getContent(), '#invoke:RfD') then
					addCategory('Articles with redirect hatnotes impacted by RfD')
				else
					addCategory('Articles with redirect hatnotes needing review')
				end
			else
				local target = targetTitle or redirTitle.redirectTarget
				if target and target ~= currentTitle then
					addCategory('Articles with redirect hatnotes needing review')
				end
			end
		end

		-- Generate the options to pass to [[Module:Hatnote]].
		if currentTitle.namespace == 0 and not mhOptions.selfref
			and redirTitle and redirTitle.namespace ~= 0
		then
			-- We are on a mainspace page, and the hatnote starts with something
			-- like "Wikipedia:Foo redirects here", so automatically label it as
			-- a self-reference.
			mhOptions.selfref = true
		else
			mhOptions.selfref = options.selfref
		end
	end
	--concatenate all the categories
	local category = ''
	for k,v in pairs(categoryTable) do
		category = category .. k
	end

	return mHatnote._hatnote(text, mhOptions) .. category
 end
 
 return p