Module:URL to diff

-- This module converts Wikipedia diff URLs to the {{diff}} template format.

local p = {}

local validDiffValues = {
	cur = true,
	prev = true,
	['next'] = true
}

local function validateId(s)
	local id = tonumber(s)
	if id and id > 0 then
		return id
	else
		return nil
	end
end

local function validateDiffParam(s)
	if not s then
		return nil
	end
	if validDiffValues[s] then
		return s
	else
		return validateId(s)
	end
end

local function decodeUrl(url)
	if type(url) ~= 'string' then
		return nil
	end
	url = mw.uri.new(url)
	if not url or url.host ~= 'en.wikipedia.org' then
		return nil
	end
	local data = {}
	data.diff = validateDiffParam(url.query.diff)
	if not data.diff then
		return nil
	end
	data.title = url.query.title and mw.uri.decode(url.query.title, 'WIKI')
	data.oldid = validateId(url.query.oldid)
	mw.logObject(data)
	return data
end

local function encodeDiffTemplate(data)
	local isNamed = false -- Track whether we need to use named parameters
	for _, key in ipairs{'title', 'label'} do
		if data[key] and string.find(data[key], '=') then
			isNamed = true
			break
		end
	end
	local ret = {}
end

function p._url(args)
	local data = decodeUrl(args.url)
	if data then
		data.label = args.label
		return encodeDiffTemplate(data)
	else
		return nil
	end
end

function p.url(frame)
	local args = require('Module:Arguments').getArgs(frame, {
		wrappers = 'Template:Make diff',
	})
	return p._url(args)
end

return p