-- Please take care when updating it! It outputs two functions: p.portal, which generates a table of portals, and p.image, which
-- produces the image name for an individual portal.

-- The portal image data is kept in submodules of Module:Portal/그림, listed below:
-- Module:Portal/그림/가		- for portal names beginning with "가"~"끼".
-- ...
-- Module:Portal/그림/하		- for portal names beginning with "하"~"히".
-- Module:Portal/그림/기타	- for portal names beginning with any other letters. This includes numbers,
-- 									 letters with diacritics, and letters in non-Latin alphabets.
-- Module:Portal/그림/별칭	- for adding aliases for existing portal names. Use this page for variations
-- 									 in spelling and diacritics, etc., no matter what letter the portal begins with.
--
-- The images data pages are separated by the first letter to reduce server load when images are added, changed, or removed.
-- Previously all the images were on one data page at Module:Portal/images, but this had the disadvantage that all
-- 5,000,000 pages using this module needed to be refreshed every time an image was added or removed.
]==]

local p = {}

local function firstLetterClass(s)
 local firstLetter = mw.ustring.sub
 
 if firstLetter == nil then return nil end
 
 if firstLetter >= '가' and firstLetter <= '힣' then
 local codepoint = mw.ustring.codepoint(firstLetter)
 local class = (codepoint - 0xAC00) / 588
 return mw.ustring.sub
 end
 
 return nil
end

local function matchImagePage(s)
	-- Finds the appropriate image subpage given a lower-case
	-- portal name plus the first letter of that portal name.
	if type(s) ~= 'string' or #s < 1 then return end
	local firstLetter = firstLetterClass(s)
	local imagePage
	if firstLetter then
		imagePage = 'Module:Portal/그림/' .. firstLetter
	else
		imagePage = 'Module:Portal/그림/기타'
	end
	return mw.loadData(imagePage)[s]
end

local function getAlias(s)
	-- Gets an alias from the image alias data page.
	local aliasData = mw.loadData('Module:Portal/그림/별칭')
	for portal, aliases in pairs(aliasData) do
		for _, alias in ipairs(aliases) do
			if alias == s then
				return portal
			end
		end
	end
end

local function getImageName(s)
	-- Gets the image name for a given string.
	if type(s) ~= 'string' or #s < 1 then
		return 'Portal-puzzle.svg'
	end
	s = mw.ustring.lower(s)
	return matchImagePage(s) or matchImagePage(getAlias(s)) or 'Portal-puzzle.svg'
end

function p._portal
	-- This function builds the portal box used by the template.
	local root = mw.html.create('div')

	-- Start the table. This corresponds to the start of the wikitext table in the old Template:Portal.
	local tableroot = root:tag('table')

	-- If no portals have been specified, display an error and add the page to a tracking category.
	if not portals[1] then
		tableroot:wikitext('분류:변수없이 사용된 포털 틀')
	end

	-- Display the portals specified in the positional arguments.
	for _, portal in ipairs(portals) do
		local image = getImageName(portal)

		-- Generate the html for the image and the portal name.
		tableroot
	end
	return tostring(root)
end

function p._image(portals)

	-- Wrapper function to allow getImageName to be accessed through #invoke.
	return getImageName(portals[1])
end

local function getAllImageTables
	-- Returns an array containing all image subpages (minus aliases) as loaded by mw.loadData.
	local images = {}
	for i, subpage in ipairs{'가', '나', '다', '라', '마', '바', '사', '아', '자', '차', '카', '타', '파', '하', '기타'} do
		images[i] = mw.loadData('Module:Portal/그림/' .. subpage)
	end
	return images
end

function p._displayAll
	-- This function displays all portals that have portal images. This function is for maintenance purposes and should not be used in
	-- articles, for two reasons: 1) there are over 1500 portals with portal images, and 2) the module doesn't record how the portal
	-- names are capitalized, so the portal links may be broken.
	local lang = mw.language.getContentLanguage
	local count = 1
	for _, imageTable in ipairs(getAllImageTables) do
		for portal in pairs(imageTable) do
			portals[count] = lang:ucfirst(portal)
			count = count + 1
		end
	end
	return p._portal
end

function p._imageDupes
	-- This function searches the image subpages to find duplicate images. If duplicate images exist, it is not necessarily a bad thing,
	-- as different portals might just happen to choose the same image. However, this function is helpful in identifying images that
	-- should be moved to a portal alias for ease of maintenance.
	local exists, dupes = {}, {}
	for _, imageTable in ipairs(getAllImageTables) do
		for portal, image in pairs(imageTable) do
			if not exists[image] then
				exists[image] = portal
			else
				table.insert(dupes, string.format)
			end
		end
	end
	if #dupes < 1 then
		return 'No duplicate images found.'
	else
		return 'The following duplicate images were found:\n* ' .. table.concat
	end
end

local function processPortalArgs(args)
	-- This function processes a table of arguments and returns two tables: an array of portal names for processing by ipairs, and a table of
	-- the named arguments that specify style options, etc. We need to use ipairs because we want to list all the portals in the order
	-- they were passed to the template, but we also want to be able to deal with positional arguments passed explicitly, for example
	-- . The behaviour of ipairs is undefined if nil values are present, so we need to make sure they are all removed.
	args = type(args) == 'table' and args or {}
	local portals = {}
	local namedArgs = {}
	for k, v in pairs(args) do
		if type(k) == 'number' and type(v) == 'string' then -- Make sure we have no non-string portal names.
			table.insert
		elseif type(k) ~= 'number' then
			namedArgs[k] = v
		end
	end
	table.sort(portals)
	for i, v in ipairs(portals) do
		portals[i] = args[v]
	end
	return portals, namedArgs
end

local function makeWrapper(funcName)
	-- Processes external arguments and sends them to the other functions.
	return function (frame)
		-- If called via #invoke, use the args passed into the invoking
		-- template, or the args passed to #invoke if any exist. Otherwise
		-- assume args are being passed directly in from the debug console
		-- or from another Lua module.
		local origArgs
		if type(frame.getParent) == 'function' then
			origArgs = frame:getParent.args
			for k, v in pairs(frame.args) do
				origArgs = frame.args
				break
			end
		else
			origArgs = frame
		end
		-- Trim whitespace and remove blank arguments.
		local args = {}
		for k, v in pairs(origArgs) do
			if type(v) == 'string' then
				v = mw.text.trim(v)
			end
			if v ~= '' then
				args[k] = v
			end
		end
		return p[funcName](processPortalArgs(args)) -- passes two tables to func: an array of portal names, and a table of named arguments.
	end
end

for _, funcName in ipairs{'portal', 'image', 'imageDupes', 'displayAll'} do
	p[funcName] = makeWrapper('_' .. funcName)
end