-- This module implements {{Category see also}}



local mHatnote = require('Module:Hatnote')



local p = {}



local function makeWikitextError(msg)

	return string.format(

		'<strong class="error">Error: %s ([[Template:Category see also]])</strong>',

		msg

	)

end



-- Gets the length of the sequence seq. Usually this should be done with the #

-- operator, but we need to work with tables that get their values through an

-- __index metamethod.

local function getSequenceLength(seq)

	local length = 0

	for i in ipairs(seq) do

		length = i

	end

	return length

end



-- Given a table of options, returns a function that formats categories for

-- those options.

--

-- Options:

-- project - a project code such as "fr" (for the French Wikipedia)

-- showPrefix - a boolean value for whether to show the "Category:" prefix

--              (and the project prefix if specified)

--

-- This is implemented as a function generator rather than a simple function

-- so that we can just process the options once, instead of every time we

-- generate a category.

local function newCategoryLinker(options)

	local formatString

	if options.project then

		if options.showPrefix then

			formatString = '[[:' .. options.project .. ':Category:%s]]'

		else

			formatString = '[[:' .. options.project .. ':Category:%s|%s]]'

		end

	else

		if options.showPrefix then

			formatString = '[[:Category:%s]]'

		else

			formatString = '[[:Category:%s|%s]]'

		end

	end

	return function (category)

		local title = mw.title.new(category)

		local pageName, display

		if not title then

			-- category is not a valid title, usually because of invalid

			-- characters like < or [. Raise an error and suppress the stack

			-- level information so that we can catch it and format the error

			-- message as wikitext.

			error(string.format(

				"'%s' is not a valid category name",

				category

			), 0)

		elseif title.namespace == 14 then -- Category namespace

			pageName = title.text

			display = title.text

		else

			pageName = title.prefixedText

			display = category

		end

		-- We can get away with using two arguments even when

		-- options.showDisplay is false, as string.format ignores extra

		-- arguments as long as there is an argument for each flag in the

		-- format string.

		return formatString:format(pageName, display)

	end

end



function p._main(args)

	local nLinks = getSequenceLength(args)



	if nLinks < 1 then

		return makeWikitextError('at least one parameter required')

	end



	local makeCategoryLink = newCategoryLinker{

		project = args.project,

		showPrefix = nLinks == 1,

	}



	local links = {}

	for i, cat in ipairs(args) do

		local success, categoryLink = pcall(makeCategoryLink, cat)

		if success then

			linksi = categoryLink

		else

			-- If there was an error, then categoryLink is the error message.

			return makeWikitextError(categoryLink)

		end

	end



	local formatString

	if nLinks == 1 then

		formatString = '%s: %s'

	else

		formatString = '%s the categories %s'

	end



	-- Don't output a comma before the "and" if we have only two links.

	local conjunction

	if nLinks == 2 then

		conjunction = ' and '

	else

		conjunction = ', and '

	end



	local hatnoteText = formatString:format(

		args.LABEL or 'See also',

		mw.text.listToText(links, ', ', conjunction)

	)

	return mHatnote._hatnote(hatnoteText, {selfref = true})

end



function p.main(frame)

	local args = require('Module:Arguments').getArgs(frame, {

		wrappers = 'Template:Category see also',

	})

	return p._main(args)

end



return p