local p = {}



local Date = require('Module:Date')._Date



function p.snowflakeToDate(frame)

	local format = frame.args.format or "%B %e, %Y"

	local epoch = tonumber(frame.args.epoch) or 1288834974

	local id_str = frame.args.id_str

	if type(id_str) ~= "string" then error("bad argument #1 (expected string, got " .. type(id_str) .. ")", 2) end

	if type(format) ~= "string" then error("bad argument #2 (expected string, got " .. type(format) .. ")", 2) end

	if type(epoch) ~= "number" then error("bad argument #3 (expected number, got " .. type(epoch) .. ")", 2) end

	local hi, lo = 0, 0

	local hiexp = 1

	local two32 = 2^32

	for c in id_str:gmatch(".") do

		lo = lo * 10 + c

		if lo >= two32 then

			hi, lo = hi * 10^hiexp + math.floor(lo / two32), lo % two32

			hiexp = 1

		else hiexp = hiexp + 1 end

	end

	hi = hi * 10^(hiexp-1)

	local timestamp = math.floor((hi * 1024 + math.floor(lo / 4194304)) / 1000) + epoch

	return os.date(format, timestamp)

end



function p.getDate(frame)

	-- just pass frame directly to snowflakeToDate, this wraps it but the args are the same plus

	if (frame.args.id_str):match("%D") then -- not a number, so return -2

		return -2

	end

	frame.args.format = "%B %e, %Y"

	if frame.args.date then 

		frame.args.date = mw.ustring.gsub(frame.args.date, "(%d%d%d%d)%a", "%1")

	end

	frame.args.epoch = tonumber(frame.args.epoch) or 1288834974

	local epochdate = Date(os.date("%B %e, %Y", frame.args.epoch))

	local twitterdate = Date(p.snowflakeToDate(frame))

	if twitterdate == epochdate then -- created before epoch, so can't determine the date

		return -1

	end

	local date = Date(frame.args.date) or 0 -- if we error here, then an input of no date causes an error, which is contrary to the entire way {{TwitterSnowflake/datecheck}} works

	return date - twitterdate

end



local function abs_datediff(x)

	if type(x) == 'number' then return math.abs(x) end

	return math.abs(x.age_days)

end



function p.datecheck(frame)

	local args = frame.args

	if not (args.date and args.id_str) then

		error('Must define date and id_str, even if they are blank.')

	end

	local errors = {

		args.error1 or 'Date mismatch of two or more days',

		args.error2 or 'No date, and posted before November 4, 2010',

		args.error3 or 'Invalid id_str'

	}

	if mw.title.getCurrentTitle():inNamespace(0) and args.error_cat then

		for i = 1, 3 do errorsi = errorsi .. '[[' .. args.error_cat .. ']]' end

	end

	if not args.date:match('^%s*$') then -- #if:{{{date|}}}

		local testResult = p.getDate{ args = { date = args.date, id_str = args.id_str }}

		if testResult == -2 then return errors3 end

		if abs_datediff(testResult) > 1 then return errors1 end

	elseif not args.id_str:match('^%s*$') then

		local testResult = p.getDate{ args = { id_str = args.id_str }}

		if testResult == -1 then return errors2 end

		if testResult == -2 then return errors3 end

	end

end



return p