-- This module implements {{section link}}.

require('strict');



local checkType = require('libraryUtil').checkType



local p = {}



local function makeSectionLink(page, section, display)

	display = display or section

	page = page or ''

	-- MediaWiki doesn't allow these in 'page', so only need to do for 'section'

	if type(section) == 'string' then

		section = string.gsub(section, "{", "{")

		section = string.gsub(section, "}", "}")

	end

	return string.format('[[%s#%s|%s]]', page, section, display)

end



local function normalizeTitle(title)

	title = mw.ustring.gsub(mw.ustring.gsub(title, "'", ""), '"', '')

	title = mw.ustring.gsub(title, "%b<>", "")

	return mw.title.new(title).prefixedText

end



function p._main(page, sections, options, title)

	-- Validate input.

	checkType('_main', 1, page, 'string', true)

	checkType('_main', 3, options, 'table', true)

	if sections == nil then

		sections = {}

	elseif type(sections) == 'string' then

		sections = {sections}

	elseif type(sections) ~= 'table' then

		error(string.format(

			"type error in argument #2 to '_main' " ..

			"(string, table or nil expected, got %s)",

			type(sections)

		), 2)

	end

	options = options or {}

	title = title or mw.title.getCurrentTitle()



	-- Deal with blank page names elegantly

	if page and not page:find('%S') then

		page = nil

		options.nopage = true

	end



	-- Make the link(s).

	local isShowingPage = not options.nopage

	if #sections <= 1 then

		local linkPage = page or ''

		if options.permalink then												-- when oldid provided

			linkPage = 'Special:Permalink/' .. options.permalink;				-- make Special:Permalink/oldid wikilink

		end

		local section = sections1];											-- sections[1] must have a value

		local display = '§&nbsp;' .. section

		if isShowingPage then

			page = page or title.prefixedText

			if options.display and options.display ~= '' then

				if normalizeTitle(options.display) == normalizeTitle(page) then

					display = options.display .. ' ' .. display

				else

					error(string.format(

						'Display title "%s" was ignored since it is ' ..

						"not equivalent to the page's actual title",

						options.display

					), 0)

				end

			else

				display = page .. ' ' .. display

			end

		end

		return makeSectionLink(linkPage, section, display)

	else

		-- Multiple sections. First, make a list of the links to display.

		local ret = {}

		for i, section in ipairs(sections) do

			reti = makeSectionLink(page, section)

		end



		-- Assemble the list of links into a string with mw.text.listToText.

		-- We use the default separator for mw.text.listToText, but a custom

		-- conjunction. There is also a special case conjunction if we only

		-- have two links.

		local conjunction

		if #sections == 2 then

			conjunction = '&#8203; and '

		else

			conjunction = ', and '

		end

		ret = mw.text.listToText(ret, nil, conjunction)



		-- Add the intro text.

		local intro = '§§&nbsp;'

		if isShowingPage then

			intro = (page or title.prefixedText) .. ' ' .. intro

		end

		ret = intro .. ret



		return ret

	end

end



function p.main(frame)

	local yesno = require('Module:Yesno')

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

		wrappers = 'Template:Section link',

		valueFunc = function (key, value)

			value = value:match('^%s*(.-)%s*$') -- Trim whitespace

			-- Allow blank first parameters, as the wikitext template does this.

			if value ~= '' or key == 1 then

				return value

			end

		end

	})



	for k, v in pairs(args) do													-- replace underscores in the positional parameter values

		if 'number' == type(k) then

			if not yesno (args'keep-underscores']) then						-- unless |keep-underscores=yes

				argsk = mw.uri.decode (v, 'WIKI');							-- percent-decode; replace underscores with space characters

			else

				argsk = mw.uri.decode (v, 'PATH');							-- percent-decode; retain underscores

			end

		end

	end



	-- Sort the arguments.

	local page

	local sections, options = {}, {}

	for k, v in pairs(args) do

		if k == 1 then

			-- Doing this in the loop because of a bug in [[Module:Arguments]]

			-- when using pairs with deleted arguments.

			page = mw.text.decode(v, true)

		elseif type(k) == 'number' then

			sectionsk = v

		else

			optionsk = v

		end

	end



	options.nopage = yesno (options.nopage);									-- make boolean

	

	-- Extract section from page, if present

	if page then

		local p, s = page:match('^(.-)#(.*)$')

		if p then page, sections1 = p, s end

	end



	-- Compress the sections array.

	local function compressArray(t)

		local nums, ret = {}, {}

		for num in pairs(t) do

			nums#nums + 1 = num

		end

		table.sort(nums)

		for i, num in ipairs(nums) do

			reti = tnum

		end

		return ret

	end

	sections = compressArray(sections)



	if not sections1 then														-- empty section parameter makes {{Section link}} meaningless

		return ('<span style="color:#d33"><span style="font-family:monospace">{{[[Template:Section link|Section link]]}}</span>: required section parameter(s) missing</span>');	-- emit error message and abandon

	end



	return p._main(page, sections, options)

end



return p