local match = require("Module:String")._match



local p = {}



--[[

Local function which is used to return a number without commas.

For example: 4,722 will become 4722.

--]]

local function cleanNumberFromCommas(title)

	return string.gsub(title, "(%d+)(,+)", "%1")

end



--[[

Local function which is used to check if the word is an article.

Returns true if it is, false if it isn't.

--]]

local function isFirstWordAnArticle(word)

	word = string.lower(word)

	if (word == "a" or word == "an" or word == "the") then

		return true

	else

		return false

	end

end



--[[

Local function which is used to return the title without its disambiguation.

--]]

local function getTitleWithoutDisambiguation(title, disambiguation)

	local newTitle = string.gsub(title, "%(".. disambiguation .. "%)", "")

	return mw.text.trim(newTitle)

end



--[[

Local function which is used to return a title without its first word.

--]]

local function getTitleWithoutFirstWord(title)

	return mw.ustring.gsub(title, "^[^%s]*%s*", "")

end



--[[

Local function which is used to return the first word from a title.

--]]

local function getFirstWord(title)

	return match(title, "^[^%s]*", 1, 1, false, "")

end



--[[

Local function which is used to return a sort key for a specific part.

--]]

local function getSortKey(title, firstWord)

	local sortKey = title

	if (isFirstWordAnArticle(firstWord) and firstWord ~= title) then

		title = getTitleWithoutFirstWord(title)

		sortKey = title .. ", " .. firstWord

	end

	

	return sortKey

end



--[[

Local function which is used to return the disambiguation sort key.

--]]

local function getDisambiguationSortKey(disambiguation)

	if (disambiguation == "") then

		return ""

	end

	

	local firstWord = getFirstWord(disambiguation)

	local disambiguationSortKey = getSortKey(disambiguation, firstWord)

	return "(" .. disambiguationSortKey .. ")"

end



--[[

Local function which is used to return the disambiguation from a title.

--]]

local function getDisambiguation(title)

	local disambiguation = match(title, "%s%((.-)%)", 1, -1, false, "")

	if (disambiguation == "") then

		return ""

	else

		return disambiguation

	end

end



--[[

The main function.

--]]

local function _main(title)

	if (not title) then

		title = mw.title.getCurrentTitle().text

	end



	local firstWord = getFirstWord(title)

	local disambiguation = getDisambiguation(title)

	local disambiguationSortKey = getDisambiguationSortKey(disambiguation)

	

	title = getTitleWithoutDisambiguation(title, disambiguation)

	title = cleanNumberFromCommas(title)

	title = getSortKey(title, firstWord)

	

	local sortKey = title .. " " .. disambiguationSortKey

	return mw.text.trim(sortKey)

end



--[[

Public function which allows modules to retrieve a sort key.

--]]

function p._getSortKey()

	return _main(nil)

end



--[[

Public function which allows templates to retrieve a sort key.

--]]

function p.getSortKey(frame)

	return _main(nil) 

end



--[[

Public function which allows templates to retrieve the sort key inside a DEFAULTSORT.

--]]

function p.getDefaultSort(frame)

	local sortKey = _main(nil)

	return frame:preprocess{text = "{{DEFAULTSORT:" .. sortKey .. "}}"} 

end



--[[

Public function which is used for testing various names and not the current page name.

--]]

function p.testcases(frame)

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

	local args = getArgs(frame)

	return _main(args1])

end



return p