-- Prosody IM
-- Copyright (C) 2008-2010 Matthew Wild
-- Copyright (C) 2008-2010 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--

local random = require "prosody.util.random";
local random_bytes = random.bytes;
local time = require "prosody.util.time";
local hex = require "prosody.util.hex".encode;
local m_ceil = math.ceil;
local m_floor = math.floor;

local function get_nibbles(n)
	return hex(random_bytes(m_ceil(n/2))):sub(1, n);
end

local function get_twobits()
	return ("%x"):format(random_bytes(1):byte() % 4 + 8);
end

local function generate()
	-- generate RFC 4122 complaint UUIDs (version 4 - random)
	return get_nibbles(8).."-"..get_nibbles(4).."-4"..get_nibbles(3).."-"..(get_twobits())..get_nibbles(3).."-"..get_nibbles(12);
end

local function generate_v7()
	-- Sortable based on time and random
	-- https://datatracker.ietf.org/doc/html/rfc9562#name-uuid-version-7
	local unix_ts_ms = m_floor(time.now()*1000);
	local unix_ts_ms_a = m_floor(unix_ts_ms / 0x10000);
	local unix_ts_ms_b = unix_ts_ms % 0x10000;
	return ("%08x-%4x-7%3s-%1s%3s-%12s"):format(unix_ts_ms_a, unix_ts_ms_b, get_nibbles(3), get_twobits(), get_nibbles(3), get_nibbles(12));
end

return {
	v4 = generate;
	v7 = generate_v7;
	get_nibbles=get_nibbles;
	generate = generate ;
	-- COMPAT
	seed = random.seed;
};