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



local newBuffer = require('Module:OutputBuffer')



local p = {}



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.title = url.query.title and mw.uri.decode(url.query.title, 'WIKI')

	data.diff = url.query.diff

	data.oldid = url.query.oldid

	data.diffonly = url.query.diffonly

	return data

end



local function encodeDiffTemplate(data)

	if not data.title and not data.diff and not data.oldid then

		return nil

	end

	local isNamed = false -- Track whether we need to use named parameters

	for k, v in pairs(data) do

		if string.find(v, '=') then

			isNamed = true

			break

		end

	end

	local getBuffer, print, printf = newBuffer()

	print('diff')

	printf('%s%s', isNamed and 'page=' or '', data.title or '')

	printf('%s%s', isNamed and 'diff=' or '', data.diff or '')

	printf('%s%s', isNamed and 'oldid=' or '', data.oldid or '')

	if data.label then

		printf('%s%s', isNamed and 'label=' or '', data.label)

	end

	if data.diffonly then

		printf('diffonly=%s', data.diffonly)

	end

	local ret = getBuffer('|')

	ret = '{{' .. ret .. '}}'

	return 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:URL to diff',

	})

	return p._url(args)

end



return p