require("strict")

local yesno = require("Module:Yesno")



-- Behaviour for these functions determined via [[Help:Pipe trick]]

local function wlPipeTrick(target)

	target = target:gsub("^[a-zA-Z0-9 _-]-:(.*)$", "%1") --Remove the namespace

	if target:find("%(.+%)$") then --If ending parenthesis

		target = target:gsub("^(.-) *%(.+%)$", "%1") --Remove ending parenthesis

	else 

		target = target:gsub("^(.-), .*$", "%1") --Else, remove ending comma

	end

	return target

end



local function wlReversePipeTrick(target)

	local current = mw.title.getCurrentTitle().prefixedText

	if current:find("%(.+%)$") then --If ending parenthesis

		target = target .. current:gsub("^.-( *%(.+%))$", "%1") --Append ending parenthesis

	else 

		target = target .. current:gsub("^.-(, .*)$", "%1") --Else, append ending comma

	end

	return target

end



local function getWikilinkInfo(wikilink)

	--[=[

		Returns the wikilink's target and its display text.

		Automatically recreates the effect of any [[Help:pipe tricks|]]

	--]=]

	local trim = mw.text.trim

	local trimmed = string.sub(wikilink, 3, -3)

	local firstPipe = string.find(trimmed, "|")

	if firstPipe then

		local target = string.sub(trimmed, 1, firstPipe-1)

		local displayText = string.sub(trimmed, firstPipe+1)

		if target == "" then -- [[|XYZ]]

			return trim(wlReversePipeTrick(displayText)), trim(displayText)

		elseif displayText == "" then -- [[XYZ|]]

			return trim(target), trim(wlPipeTrick(target))

		else --[[ABC|XYZ]]

			return trim(target), trim(displayText)

		end

	else

		local out = trim(trimmed)

		if out:find("^/.-/+$") and mw.title.getCurrentTitle().namespace ~= 0 then -- [[/Test/]]

			return out, out:gsub("^/(.-)/+$", "%1")

		else -- [[Test]]

			return out, nil

		end

	end

end



local function linkOnce(text, options) -- Module entry point

	--[=[

		We are going to traverse the text linearly ourselves.

		Using %b[] isn't preferable as nested brackets (E.g. the wikilink to t

		in [[File:x|Cap[[t]]ion]]) would be missed and doing a check for

		%[%[.-%]%] wouldn't work for the exact same testcase for other reasons

	--]=]

	local options = options or {follow_redirects=true}

	local newText = {}

	local scannerPosition = 1

	local existingWikilinks = {}

	local openWikilinks = {}

	while true do

		local Position, _, Character = string.find(text, "([%[%]])%1", scannerPosition)

		local container = (openWikilinks#openWikilinks or {Text=newText}).Text

		if not Position then --Done

			container#container+1 = string.sub(text, scannerPosition)

			break

		end

		container#container+1 = string.sub(text, scannerPosition, Position-1)



		scannerPosition = Position+2 --+2 to pass the [[ / ]]

		if Character == "[" then --Add a [[ to the pending wikilink queue

			openWikilinks#openWikilinks+1 = {Position = Position, Text = {"[["}}



		else --Pair up the ]] to any available [[

			if #openWikilinks >= 1 then

				local openingPair = table.remove(openWikilinks) --Pop the latest [[

				local wlStart, wlText = openingPair.Position, table.concat(openingPair.Text, "") .. "]]"

				local wikilink = string.sub(text, wlStart, Position+1)

				local wlTarget, wlPiped = getWikilinkInfo(wikilink)



				local newContainer = (openWikilinks#openWikilinks or {Text=newText}).Text

				if wlTarget:find("^[Ii]mage:") or wlTarget:find("^[Ff]ile:") or wlTarget:find("^[Cc]ategory:") then --Files/Images/Categories aren't processed (they aren't really wikilinks)

					newContainer#newContainer+1 = wlText

				else

					local realTarget = wlTarget:sub(1, 1):upper() .. wlTarget:sub(2)

					if existingWikilinksrealTarget then

						newContainer#newContainer+1 = wlPiped or wlTarget

					else

						local resolvedTarget = realTarget

						if options.follow_redirects then

							local titleObj = mw.title.new(wlTarget)

							if titleObj then

								local newTarget = titleObj.isRedirect and titleObj.redirectTarget.fullText or titleObj.fullText

								resolvedTarget = newTarget:sub(1, 1):upper() .. newTarget:sub(2)

							end

						end

						if existingWikilinksresolvedTarget then

							newContainer#newContainer+1 = wlPiped or wlTarget

						else

							existingWikilinksrealTarget = true

							existingWikilinksresolvedTarget = true

							newContainer#newContainer+1 = wlText

						end

					end

				end



			else --Just a random ]] with no matching pair, dont process it

				newText#newText+1 = "]]"

			end

		end

	end



	if #openWikilinks > 0 then --Random [[ with no matching pair, dont process it

		for i = #openWikilinks, 2, -1 do

			local nextLink = openWikilinksi-1

			nextLink.Text#nextLink.Text+1 = table.concat(openWikilinksi].Text, "")

		end

		newText#newText+1 = table.concat(openWikilinks1].Text, "")

	end

	return table.concat(newText, "")

end



local function main(frame) -- Template entry point

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

	return linkOnce(args1 or "", {

		follow_redirects = yesno(args.follow_redirects) or true,

	})

end



return {

	-- Main entry points

	main = main,

	linkOnce = linkOnce,

	-- Helper functions

	wlPipeTrick = wlPipeTrick,

	wlReversePipeTrick = wlReversePipeTrick,

	getWikilinkInfo = getWikilinkInfo

}