local p = {}

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

local yesNo = require('Module:Yesno')

local getPlain = require('Module:Text').Text().getPlain



-- function to determine whether "sub" occurs in "s"

local function plainFind(s, sub)

	return mw.ustring.find(s, sub, 1, true)

end



-- function to count the number of times "pattern" (a regex) occurs in "s"

local function countMatches(s, pattern)

	local _, count = mw.ustring.gsub(s, pattern, '')

	return count

end



local singular = 1

local likelyPlural = 2

local plural = 3



-- Determine whether a string is singular or plural (i.e., it represents one

-- item or many)

-- Arguments:

--   origArgs[1]: string to process

--   origArgs.no_comma:  if false, use commas to detect plural (default false)

--   origArgs.parse_links: if false, treat wikilinks as opaque singular objects (default false)

-- Returns:

--   singular, likelyPlural, or plural (see constants above), or nil for completely unknown

function p._main(origArgs)

	origArgs = type(origArgs) == 'table' and origArgs or {}

	local args = {}

	-- canonicalize boolean arguments

	for key, default in pairs({no_comma=false,parse_links=false,any_comma=false,no_and=false}) do

		if origArgskey == nil then

			argskey = default

		else

			argskey = yesNo(origArgskey],default)

		end

	end

	local checkComma = not args.no_comma

	local checkAnd = not args.no_and

	local rewriteLinks = not args.parse_links

	local anyComma = args.any_comma

	local s = origArgs1  -- the input string

	if not s then

		return nil -- empty input returns nil

	end

	s = tostring(s)

	s = mw.text.decode(s,true)  --- replace HTML entities (to avoid spurious semicolons)

	if plainFind(s,'data-plural="0"') then -- magic data string to return true

		return singular

	end

	if plainFind(s,'data-plural="1"') then -- magic data string to return false

		return plural

	end

	-- count number of list items

	local numListItems = countMatches(s,'<%s*li')

	-- if exactly one, then singular, if more than one, then plural

	if numListItems == 1 then

		return singular

	end

	if numListItems > 1 then

		return plural

	end

	-- if "list of" occurs inside of wlink, then it's plural

	if mw.ustring.find(s:lower(), '%[%[[^%]]*list of[^%]]+%]%]') then

		return plural

	end

	-- fix for trailing br tags passed through [[template:marriage]]

	s = mw.ustring.gsub(s, '<%s*br[^>]*>%s*(</div>)', '%1')

	-- replace all wikilinks with fixed string

	if rewriteLinks then

		s = mw.ustring.gsub(s,'%b[]','WIKILINK') 

	end

	-- Five conditions: any one of them can make the string a likely plural or plural

	local hasBreak = mw.ustring.find(s,'<%s*br')

	-- For the last 4, evaluate on string stripped of wikimarkup

	s = getPlain(s)

	local hasBullets = countMatches(s,'%*+') > 1

	local multipleQids = mw.ustring.find(s,'Q%d+[%p%s]+Q%d+') -- has multiple QIDs in a row

	if hasBullets or multipleQids then

		return plural

	end

	local commaPattern = anyComma and '[,;]' or '%D[,;]%D'  -- semi-colon similar to comma

	local hasComma = checkComma and mw.ustring.find(s, commaPattern)

	local hasAnd = checkAnd and mw.ustring.find(s,'[,%s]and%s')

	if hasBreak or hasComma or hasAnd then

		return likelyPlural

	end

	return singular

end



function p._pluralize(args)

	args = type(args) == 'table' and args or {}

	local singularForm = args3 or args.singular or ""

	local pluralForm = args4 or args.plural or ""

	local likelyForm = args.likely or pluralForm

	local link = args5 or args.link

	if link then

		link = tostring(link)

		singularForm = '[['..link..'|'..singularForm..']]'

		pluralForm = '[['..link..'|'..pluralForm..']]'

		likelyForm = '[['..link..'|'..likelyForm..']]'

	end

	if args2 then

		return pluralForm

	end

	local detect = p._main(args)

	if detect == nil then

		return ""   -- return blank on complete failure

	end

	if detect == singular then

		return singularForm

	elseif detect == likelyPlural then

		return likelyForm

	else

		return pluralForm

	end

end



function p.main(frame)

	local args = getArgs(frame)

	-- For template, return 1 if singular, blank if plural or empty

	local result = p._main(args)

	if result == nil then

		return 1

	end

	return result == singular and 1 or ""

end



function p.pluralize(frame)

	local args = getArgs(frame)

	return p._pluralize(args)

end



return p