--[[
-- 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 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)
	-- Get the args table and work out the maximum arg key.
	local origArgs = frame:getParent().args
	local args = {}
	local maxArg = 0
	for k, v in pairs(origArgs) do
		if type(k) == 'number' and k > maxArg then
			maxArg = k
		end
		v = v:match('^%s*(.-)%s*$') -- Trim whitespace
		if v ~= '' then
			args[k] = v
		end
	end

	--Get table of redirects
	local numRedirects = tonumber(frame.args[1]) or 1
	local redirect = {}
	for i = 1, numRedirects do
		-- Return an error if no redirect was specified.
		if not args[i] then
			return mHatnote.makeWikitextError(
				'no redirect specified',
				'Template:Redirect#Errors',
				args.category
			)
		end
		redirect[i] = args[i]
	end


	-- Create the data table.
	local data = {}
	local iArg = numRedirects - 1
	local iData = 1
	repeat
		iArg = iArg + 2
		local useTable = data[iData] or {}
		local pages = useTable.pages or {}
		local use = args[iArg]
		local page = args[iArg + 1]
		local nextUse = args[iArg + 2]
		--Tracking for and-gaps
		if (page == nil) and (nextUse == 'and' or use == 'and') then
			--It's an "unusual cat". Get it? :P
			local cheshire = '[[Category:Hatnote templates using unusual parameters]]'
			if use ~= nil and use ~= 'and' then
				use = use .. cheshire
			elseif useTable.use ~= nil then
				useTable.use = useTable.use .. cheshire
			else
				--Previous tracking suggests this won't change behaviour in
				--practice, for any extant uses, but it does change behaviour in
				--theory.
				use = 'other uses' .. cheshire
			end
		end
		pages[#pages + 1] = page
		useTable.pages = pages
		if use ~= 'and' then
			useTable.use = use
		end
		data[iData] = useTable
		if nextUse ~= 'and' then
			iData = iData + 1
		end
	until iArg >= maxArg - 1

	-- Create the options table.
	local options = {}
	options.selfref = args.selfref
		
	return p._redirect(redirect, data, options)
end

local function formatUseTable(useTable, isFirst, redirect)
	-- Formats one use table. Use tables are the tables inside the data array.
	-- Each one corresponds to one use. (A use might be the word "cats" in the
	-- phrase "For cats, see [[Felines]]".)
	-- Returns a string, or nil if no use was specified.
	-- The isFirst parameter is legacy, but partly maintained for its effect of
	-- cancelling empty use items.
	useTable = useTable or {}
	local use
	if not (useTable.use or isFirst) then
		if (not isFirst) and useTable.pages and #useTable.pages ~= 0 then
			return '[[Category:Hatnote templates using unusual parameters]]'
		else
			return nil
		end
	end
	use = useTable.use or 'other uses'
	local pages = useTable.pages or {}
	redirect = redirect[1] or error(
		'no redirect was supplied',
		2
	)
	pages[1] = pages[1] or redirect .. ' (disambiguation)'
	pages = mHatnote.formatPages(unpack(pages))
	pages = mw.text.listToText(pages)
	return string.format(
		'For %s, see %s.',
		use,
		pages
	)
end

function p._redirect(redirect, data, options, currentTitle, redirectTitle, targetTitle)
	-- Validate the input. Don't bother checking currentTitle, redirectTitle or
	-- targetTitle, as they are only used in testing.
	checkTypeMulti('_redirect', 1, redirect, {'string', 'table'})
	-- String type can stay valid until extant use-cases are checked-for and
	-- updated, but we'll coerce them to table for now
	if type(redirect) == 'string' then redirect = {redirect} end
	checkType('_redirect', 2, data, 'table', true)
	checkType('_redirect', 3, options, 'table', true)
	data = data or {}
	options = options or {}
	currentTitle = currentTitle or mw.title.getCurrentTitle()

	-- Generate the text.
	local text = {}
	local formattedRedirect = {}
	for k,v in pairs(redirect) do
		formattedRedirect[k] = '"' .. v .. '"'
	end
	text[#text + 1] = mw.text.listToText(formattedRedirect) .. ' ' .. (#redirect == 1 and 'redirects' or 'redirect') .. ' here.'
	text[#text + 1] = formatUseTable(data[1] or {}, true, redirect)
	if data[1] and data[1].use then
		for i = 2, #data do
			text[#text + 1] = formatUseTable(data[i] or {}, false, redirect)
		end
	end
	text = table.concat(text, ' ')
	
	local categoryTable = {}
	--add categories to a table by index, so we don't get duplicates
	function addCategory(cat)
		if cat and cat ~= '' then
			categoryTable[string.format('[[Category:%s]]', cat)] = true
		end
	end

	local mhOptions = {}
	for k,v in pairs(redirect) do
		-- Generate the tracking category.
		-- 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 "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