local export = {}

local data = mw.loadData("Modulo:ja/data")

function export.kana_to_romaji(text, nodiacr, keepdot)
	if type(text) == "table" then -- assume a frame.
		text, nodiacr = text.args[1], text.args[2]
	end

	-- remove %
	text = mw.ustring.gsub(text, '%%', '')

	text = mw.ustring.gsub(text, "%^'''", "'''^")

	-- local kr_minus_period = data.kr
	-- kr_minus_period["。"] = "。"

	-- convert Japanese spaces to western spaces
	text = mw.ustring.gsub(text, '　', ' ')

	-- if there is a は separated by halfwidth spaces, romanize it as " wa "
	text = mw.ustring.gsub(text, ' は ', ' wa ')
	-- also if it follows a space and is the last character, e.g. それでは
	text = mw.ustring.gsub(text, ' は$', ' wa')
	-- or " は、"
	text = mw.ustring.gsub(text, ' は、', ' wa, ')
	-- or " は。"
	text = mw.ustring.gsub(text, ' は。', ' wa. ')
	text = mw.ustring.gsub(text, ' は？', ' wa? ')
	text = mw.ustring.gsub(text, ' は）', ' wa)')
	-- or " '''は''' "
	text = mw.ustring.gsub(text, " '''は''' ", " '''wa''' ")
	-- romanize では as "dewa"
	text = mw.ustring.gsub(text, ' では ', ' dewa ')
	text = mw.ustring.gsub(text, ' では$', ' dewa')
	text = mw.ustring.gsub(text, ' では、', ' dewa, ')
	text = mw.ustring.gsub(text, ' では。', ' dewa. ')
	text = mw.ustring.gsub(text, ' では？', ' dewa? ')
	text = mw.ustring.gsub(text, ' では）', ' dewa)')
	text = mw.ustring.gsub(text, "'''では'''", "'''dewa'''")
	-- romanize で は (with space) as "de wa"
	text = mw.ustring.gsub(text, "'''で は'''", "'''de wa'''")
	-- same sort of thing for へ
	text = mw.ustring.gsub(text, ' へ ', ' e ')
	text = mw.ustring.gsub(text, " '''へ''' ", " '''e''' ")
	text = mw.ustring.gsub(text, ' へ$', ' e')
	text = mw.ustring.gsub(text, ' へ、', ' e, ')
	text = mw.ustring.gsub(text, ' へ。', ' e. ')
	text = mw.ustring.gsub(text, ' へ？', ' e?')
	text = mw.ustring.gsub(text, ' へ）', ' e)')
	-- dangling small tsu is romanized as nothing
	text = mw.ustring.gsub(text, 'ッ。', '。')
	text = mw.ustring.gsub(text, 'ッ！', '！')
	text = mw.ustring.gsub(text, 'ッ」', '」')
	text = mw.ustring.gsub(text, 'ッ、', '、')

	-- ゝ means "repeat the previous character" and is used with hiragana, like 々 is for kanji
	text = mw.ustring.gsub(text, '(.)ゝ', '%1%1')
	text = mw.ustring.gsub(text, '(.)ゞ', function(char) return mw.ustring.toNFC(char .. char .. '゙') end)

	-- romanising ヶ
	text = mw.ustring.gsub(text, 'ヶげつ', 'kagetsu')
	text = mw.ustring.gsub(text, 'ヶ', 'ga')

	-- convert hiragana to katakana
	text = require('modulo:ja').hira_to_kata(text)
	-- replace katakana with romaji (?? not sure what the pattern below does ??)
	-- this is hackish, but we're using the period to indicate morpheme boundaries to prevent macrons
	-- from forming across them, so we'll remove the ASCII periods used for markup but not the Japanese periods

	-- convert the Japanese periods at the end
	--table.remove(kr_minus_period, "。")
	text = mw.ustring.gsub(text, '.[ィェォャュョァヮゥ゜]?ェ?',
	                       function (char)
	                       	if char == "。" then
	                       		return char
	                       	else
	                       		return data.kr_old[char] or char
	                       	end
	                       end)

	text = require('modulo:ja').fullwidth_to_halfwidth(text)

	-- replace long vowel mark with the vowel that comes before
	text = mw.ustring.gsub(text, '([aeiou])ー', '%1%1')

	-- add vowels with diacritics
	if not nodiacr then
		text = mw.ustring.gsub(text, 'oo', 'ō')
		text = mw.ustring.gsub(text, 'aa', 'ā')
		text = mw.ustring.gsub(text, 'ee', 'ē')
		text = mw.ustring.gsub(text, 'ou', 'ō')
		text = mw.ustring.gsub(text, 'uu', 'ū')
		text = mw.ustring.gsub(text, 'ii', 'ī')
	end

	if not keepdot then
		-- if input had spaces, keep them
		-- if the input string had periods, then remove them now
		text = mw.ustring.gsub(text, '%.', '')
		-- now that markup periods are gone, convert the Japanese periods to western periods
		text = mw.ustring.gsub(text, "。", ". ")
	end

	-- romanize sokuon or geminate consonants
	-- text = mw.ustring.gsub(text, '^ッ', '')
	-- double the previous consonant letter if there is a small tsu
	text = mw.ustring.gsub(text, 'ッ([kstpgdbjzrfh])', '%1%1')
	text = mw.ustring.gsub(text, 'ッ\'\'\'([kstpgdbjzrfh])', '%1\'\'\'%1')
	-- replace ッc with tc
	text = mw.ustring.gsub(text, 'ッc', 'tc')
	text = mw.ustring.gsub(text, 'ッ\'\'\'c', 't\'\'\'c')
	-- if small tsu comes at the end, just throw it away
	-- text = mw.ustring.gsub(text, 'ッ$', '')

	-- the @ is used to determine when to insert an opostrophe after ん or ン
	-- (all is kata at that point)
	-- insert apostrophe when ン is followed by a vowel or
	-- y, which corresponds to the cases んや (n'ya) んゆ (n'yu) and んよ (n'yo)
	text = mw.ustring.gsub(text, "@([aeiouāēīōūy])", "'%1")
	-- remove @
	text = mw.ustring.gsub(text, "@", "")

	-- capitalize any letter following a ^ symbol
	text = mw.ustring.gsub(text, "%^%l", mw.ustring.upper)
	-- remove ^
	text = mw.ustring.gsub(text, "%^", "")

	-- clean up spaces
	text = mw.text.trim(text)
	text = mw.ustring.gsub(text, ' +', ' ')

	return text
end

return export