local export = {}

local function fake_frame(args, parent_args)
	return {
		args = args,
		getParent = function()
			return {
				args = parent_args,
			}
		end
	}
end

function get_by_code(code)
	return require("Module:languages").getByCode(code, nil, true, true) or require("Module:scripts").getByCode(code)
end

local function get_code_from_title_without_namespace(title_without_namespace)
	local prefix = title_without_namespace:match("^(.+)%-translit%f")
	if not prefix then
		error("Base segment of title should end in -translit: " .. title_without_namespace)
	end
	local code = prefix
	local lang_or_family_or_script = get_by_code(code)
	if not lang_or_family_or_script then
		-- Accommodate modules with multiple codes in the title.
		-- The first code should be used.
		-- Right now it strips segments from the end until it finds a match:
		-- Module:Deva-Beng-translit -> Deva-Beng -> Deva
		-- Module:pra-Deva-translit -> pra-Deva -> pra
		-- Module:Deva-mnc-Mong-translit -> Deva-mnc-Mong -> Deva-mnc -> Deva
		while true do
			new_code = code:match("^(.+)%-+$")
			if new_code then
				code = new_code
			else
				break
			end
			lang_or_family_or_script = get_by_code(new_code)
			if lang_or_family_or_script then
				break
			end
		end
	end
	
	return code, lang_or_family_or_script
end

function export.documentation(title_without_namespace, explanation)
	local code, lang_or_family_or_script = get_code_from_title_without_namespace(title_without_namespace)
	return export.documentation_from_code(code, explanation, title_without_namespace)
end

function export.documentation_from_code(code, explanation, title_without_namespace)
	local lang_or_family_or_script = get_by_code(code)
	
	if not lang_or_family_or_script then
		return "Language code in page name (<code>" .. code .. "</code>) not recognized."
	end
	
	local category_name = lang_or_family_or_script:getCategoryName()
	
	local transliteration_input
	if lang_or_family_or_script:hasType("script") then
		transliteration_input = "text in the ]"
	elseif lang_or_family_or_script:hasType("family") then
		transliteration_input = "text in one of the ]"
	else -- language
		transliteration_input = "] text"
	end
	
	local tr_page = "WT:" .. mw.ustring.upper(code) .. " TR"
	
	return "This module will transliterate " .. transliteration_input
		.. (explanation and " " .. explanation or "")
		.. (mw.title.new(tr_page).exists and " per ]" or "")
		.. ". "
		.. require("Module:documentation").translitModuleLangList({args = {  = title_without_namespace:gsub("/documentation$", "") }})
		.. [=[

The module should preferably not be called directly from templates or other modules.
To use it from a template, use <code>{{]}}</code>.
Within a module, use ].

For testcases, see =] .. title_without_namespace:gsub("/documentation$", "") .. ].

== Functions ==
; <code>tr(text, lang, sc)</code>
: Transliterates a given piece of <code>text</code> written in the script specified by the code <code>sc</code>, and language specified by the code <code>lang</code>.
: When the transliteration fails, returns <code>nil</code>.]=]
		.. require("Module:module categorization").categorize(fake_frame({
				is_template = "1",
				 = title_without_namespace,
			}, {
				 = code,
			}))
end

function export.documentation_template(frame)
	-- Parameters to {{translit module documentation}}:
	-- |code|description
	-- Ignore code because we get it from the page name.
	local pagename = mw.title.getCurrentTitle().text
	local args = frame:getParent().args
	if args and get_code_from_title_without_namespace(pagename) ~= args then
		-- ]
		require("Module:debug").track("translit/input different from title")
	end
	if args then
		return export.documentation_from_code(args, args, pagename)
	else
		return export.documentation(pagename, args)
	end
end

return export