-- This module de-links most wikitext.



require("strict")



local p = {}



local getArgs



local function delinkReversePipeTrick(s)

	if s:match("^%[%[|.*[|\n]") then -- Check for newlines or multiple pipes.

		return s

	end

	return s:match("%[%[|(.*)%]%]")



end



local function delinkPipeTrick(s)

	-- We need to deal with colons, brackets, and commas, per [[Help:Pipe trick]].

	-- First, remove the text before the first colon, if any.

	if s:match(":") then

		s = s:match("%[%[.-:(.*)|%]%]")

	-- If there are no colons, grab all of the text apart from the square brackets and the pipe.

	else

		s = s:match("%[%[(.*)|%]%]")

	end

	

	-- Next up, brackets and commas.

	if s:match("%(.-%)$") then -- Brackets trump commas.

		s = s:match("(.-) ?%(.-%)$")

	elseif s:match(",") then -- If there are no brackets, display only the text before the first comma.

		s = s:match("(.-),.*$")

	end

	return s

end



-- Return wikilink target |wikilinks=target

local function getDelinkedTarget(s)

	local result = s

	-- Deal with the reverse pipe trick.

	if result:match("%[%[|") then

		return delinkReversePipeTrick(result)

	end

	

	result = mw.uri.decode(result, "PATH") -- decode percent-encoded entities. Leave underscores and plus signs.

	result = mw.text.decode(result, true) -- decode HTML entities.

	

	-- Check for bad titles. To do this we need to find the

	-- title area of the link, i.e. the part before any pipes.

	local target_area

	if result:match("|") then -- Find if we're dealing with a piped link.

		target_area = result:match("^%[%[(.-)|.*%]%]")

	else

		target_area = result:match("^%[%[(.-)%]%]")

	end



	-- Check for bad characters.

	if mw.ustring.match(target_area, "[%[%]<>{}%%%c\n]") and mw.ustring.match(target_area, "[%[%]<>{}%%%c\n]") ~= "?" then

		return s

	end

	

	return target_area

end



local function getDelinkedLabel(s)

	local result = s

	-- Deal with the reverse pipe trick.

	if result:match("%[%[|") then

		return delinkReversePipeTrick(result)

	end



	result = mw.uri.decode(result, "PATH") -- decode percent-encoded entities. Leave underscores and plus signs.

	result = mw.text.decode(result, true) -- decode HTML entities.



	-- Check for bad titles. To do this we need to find the

	-- title area of the link, i.e. the part before any pipes.

	local target_area

	if result:match("|") then -- Find if we're dealing with a piped link.

		target_area = result:match("^%[%[(.-)|.*%]%]")

	else

		target_area = result:match("^%[%[(.-)%]%]")

	end



	-- Check for bad characters.

	if mw.ustring.match(target_area, "[%[%]<>{}%%%c\n]") and mw.ustring.match(target_area, "[%[%]<>{}%%%c\n]") ~= "?" then

		return s

	end



	-- Check for categories, interwikis, and files.

	local colon_prefix = result:match("%[%[(.-):.*%]%]") or "" -- Get the text before the first colon.

	local ns = mw.site.namespacescolon_prefix -- see if this is a known namespace

	if mw.language.isKnownLanguageTag(colon_prefix) or (ns and (ns.canonicalName == "File" or ns.canonicalName == "Category")) then

		return ""

	end



	-- Remove the colon if the link is using the [[Help:Colon trick]].

	if result:match("%[%[:") then

		result = "[[" .. result:match("%[%[:(.*%]%])")

	end



	-- Deal with links using the [[Help:Pipe trick]].

	if mw.ustring.match(result, "^%[%[[^|]*|%]%]") then

		return delinkPipeTrick(result)

	end

	

	-- Find the display area of the wikilink

	if result:match("|") then -- Find if we're dealing with a piped link.

		result = result:match("^%[%[.-|(.+)%]%]")

		-- Remove new lines from the display of multiline piped links,

		-- where the pipe is before the first new line.

		result = result:gsub("\n", "")

	else

		result = result:match("^%[%[(.-)%]%]")

	end



	return result

end



local function delinkURL(s)

	-- Assume we have already delinked internal wikilinks, and that

	-- we have been passed some text between two square brackets [foo].

	

	-- If the text contains a line break it is not formatted as a URL, regardless of other content.

	if s:match("\n") then

		return s

	end

	

	-- Check if the text has a valid URL prefix and at least one valid URL character.

	local valid_url_prefixes = {"//", "http://", "https://", "ftp://", "gopher://", "mailto:", "news:", "irc://"} 

	local url_prefix

	for _ ,v in ipairs(valid_url_prefixes) do

		if mw.ustring.match(s, '^%[' .. v ..'[^"%s].*%]' ) then

			url_prefix = v

			break

		end

	end

	

	-- Get display text

	if not url_prefix then

		return s

	end

	s = s:match("^%[" .. url_prefix .. "(.*)%]") -- Grab all of the text after the URL prefix and before the final square bracket.

	s = s:match('^.-(["<> ].*)') or "" -- Grab all of the text after the first URL separator character ("<> ).

	s = mw.ustring.match(s, "^%s*(%S.*)$") or "" -- If the separating character was a space, trim it off.

	

	local s_decoded = mw.text.decode(s, true)

	if mw.ustring.match(s_decoded, "%c") then

		return s

	end



	return s_decoded



end



local function delinkLinkClass(text, pattern, delinkFunction)

	if type(text) ~= "string" then

		error("Attempt to de-link non-string input.", 2)

	end

	if type(pattern) ~= "string" or mw.ustring.sub(pattern, 1, 1) ~= "^" then

		error('Invalid pattern detected. Patterns must begin with "^".', 2)

	end

	-- Iterate over the text string, and replace any matched text. using the 

	-- delink function. We need to iterate character by character rather 

	-- than just use gsub, otherwise nested links aren't detected properly.

	local result = ""

	while text ~= "" do

		-- Replace text using one iteration of gsub.

		text = mw.ustring.gsub(text, pattern, delinkFunction, 1)

		-- Append the left-most character to the result string.

		result = result .. mw.ustring.sub(text, 1, 1)

		text = mw.ustring.sub(text, 2, -1)

	end

	return result

end



function p._delink(args)

	local text = args1 or ""

	if args.refs == "yes" then

		-- Remove any [[Help:Strip markers]] representing ref tags. In most situations 

		-- this is not a good idea - only use it if you know what you are doing!

		text = mw.ustring.gsub(text, "UNIQ%w*%-ref%-%d*%-QINU", "")

	end

	if args.comments ~= "no" then

		text = text:gsub("<!%-%-.-%-%->", "") -- Remove html comments.

	end



	if args.wikilinks ~= "no" and args.wikilinks ~= "target" then

		-- De-link wikilinks and return the label portion of the wikilink.

		text = delinkLinkClass(text, "^%[%[.-%]%]", getDelinkedLabel)

	elseif args.wikilinks == "target" then

		-- De-link wikilinks and return the target portions of the wikilink.

		text = delinkLinkClass(text, "^%[%[.-%]%]", getDelinkedTarget)

	end

	if args.urls ~= "no" then

		text = delinkLinkClass(text, "^%[.-%]", delinkURL) -- De-link URLs.

	end

	if args.whitespace ~= "no" then

		-- Replace single new lines with a single space, but leave double new lines

		-- and new lines only containing spaces or tabs before a second new line.

		text = mw.ustring.gsub(text, "([^\n \t][ \t]*)\n([ \t]*[^\n \t])", "%1 %2")

		text = text:gsub("[ \t]+", " ") -- Remove extra tabs and spaces.

	end

	return text

end



function p.delink(frame)

	if not getArgs then

		getArgs = require('Module:Arguments').getArgs

	end

	return p._delink(getArgs(frame, {wrappers = 'Template:Delink'}))

end



return p