Module:Redirect hatnote
--[[
 -- This module produces a &quot;redirect&quot; hatnote. It looks like this:
 -- '&quot;X&quot; 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 = {}
 
 local function getTitle(...)
 	local success, titleObj = pcall(mw.title.new, ...)
 	if success then
 		return titleObj
 	else
 		return nil
 	end
 end
 
 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] = '&quot;' .. v .. '&quot;'
 	end
 	local text = {
 		mHatList.andList(formattedRedirect) .. ' ' .. (#redirect == 1 and 'redirects' or 'redirect') .. ' here.',
 		mHatList._forSee(args, #redirect + 1, {title = redirect[1]})
 	}
 	text = table.concat(text, ' ')
 	-- Functionality for adding categories	
 	local categoryTable = {}
 	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 = {}
 	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
 			redirectTitle = redirectTitle or getTitle(v)
 			if not redirectTitle or not redirectTitle.exists then
 				addCategory('Missing redirects')
 			elseif not redirectTitle.isRedirect then
 				addCategory('Articles with redirect hatnotes needing review')
 			else
 				local mRedirect = require('Module:Redirect')
 				local target = mRedirect.getTarget(redirectTitle)
 				targetTitle = targetTitle or target and getTitle(target)
 				if targetTitle and targetTitle ~= 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 redirectTitle and redirectTitle.namespace ~= 0
 		then
 			-- We are on a mainspace page, and the hatnote starts with something
 			-- like &quot;Wikipedia:Foo redirects here&quot;, 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