Module:a or an/sandbox

This is the module sandbox page for Module:A or an (diff).
See also the companion subpage for test cases (run).
local p = {}
local words = mw.loadData('Module:A or an/words')

local lcVChars = 'aeiouà-æè-ïò-öø-üāăąēĕėęěĩīĭįıĳōŏőœũūŭůűų'
local ucVvChars = 'AEFHILMNORSXÀ-ÆÈ-ÏÒ-ÖØĀĂĄĒĔĖĘĚĨĪĬĮıĲŌŎŐŒÑĤĦĹĻĽĿŁŃŅŇŊŔŖŘŚŜŞ'

local article = {
	a = "a",
	an = "an",
}

local function findWord(text, array)
	for _, v in ipairs(array) do
		if mw.ustring.find(text, '^' .. v .. '$') then
			return true
		end
	end
end

local function get_article_from_acronym(text)
	if mw.ustring.find(text, '^[' .. ucVvChars .. ']')
		and not findWord(text, words.cvAcronyms) -- Exclude 'NASA' etc.
		or findWord(text, words.vvAcronyms) -- 'UNRWA' etc.
	then
		return article.an
	end
	return article.a
end

local function get_article_from_number_word(text)
	text = mw.ustring.match(text, '^[0-9]+') -- Extract the number
	if findWord(text, words.vNums) then -- '18' etc.
		return article.an
	end
	return article.a
end

local function clean_text(text)
	text = mw.ustring.gsub(text, '</?[A-Za-z][^>]->', '') -- Remove HTML tags
	text = mw.ustring.gsub(text, '%[%[[^%|]+%|(..-)%]%]', '%1') -- Remove wikilinks
	text = mw.ustring.gsub(mw.ustring.gsub(text, '%[%[', ''), '%]%]', '')
	text = mw.ustring.gsub(text, '^["%$\'%(<%[%{¢-¥₠-₿]+', '') -- Strip some symbols at the beginning
	text = mw.ustring.match(text, '^%.?[0-9%u%l]+') or text -- Extract the first word
	return text
end

function p._main(args)
	local original_text = args[1] and mw.text.trim(args[1])
	local text = original_text
	local article = article.a
	local ret = ''

	if text and text ~= '' then
		text = clean_text(text)

		if mw.ustring.find(text, '^[0-9]') then -- It begins with a number
			article = get_article_from_number_word(text)
		elseif mw.ustring.match(text, '^[0-9%u]+$') then -- It looks like an acronym
			article = get_article_from_acronym(text)
		else
			text = mw.ustring.lower(text) -- Uncapitalize
			if mw.ustring.find(text, '^['.. lcVChars .. ']') then -- It begins with a vowel
				if not findWord(text, words.vcWords) -- Exclude 'euro' etc.
					or findWord(text, words.vvWords) -- But not 'Euler' etc.
				then
					article = article.an
				end
			elseif args.variety and mw.ustring.lower(args.variety) == 'us' -- 'herb' etc.
				and findWord(text, words.cvWordsUS)
				or findWord(text, words.cvWords) -- 'hour' etc.
			then
				article = article.an
			end
		end
		ret = article .. ' ' .. original_text
	end
	
	return ret
end

function p.main(frame)
	return p._main(frame:getParent().args)
end

return p