diff -r 000000000000 -r 550f506de75a util/logger.lua
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/util/logger.lua	Thu Dec 03 17:05:27 2020 +0000
@@ -0,0 +1,90 @@
+-- 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.
+--
+-- luacheck: ignore 213/level
+
+local pairs = pairs;
+local ipairs = ipairs;
+local require = require;
+
+local _ENV = nil;
+-- luacheck: std none
+
+local level_sinks = {};
+
+local make_logger;
+
+local function init(name)
+	local log_debug = make_logger(name, "debug");
+	local log_info = make_logger(name, "info");
+	local log_warn = make_logger(name, "warn");
+	local log_error = make_logger(name, "error");
+
+	return function (level, message, ...)
+			if level == "debug" then
+				return log_debug(message, ...);
+			elseif level == "info" then
+				return log_info(message, ...);
+			elseif level == "warn" then
+				return log_warn(message, ...);
+			elseif level == "error" then
+				return log_error(message, ...);
+			end
+		end
+end
+
+function make_logger(source_name, level)
+	local level_handlers = level_sinks[level];
+	if not level_handlers then
+		level_handlers = {};
+		level_sinks[level] = level_handlers;
+	end
+
+	local logger = function (message, ...)
+		for i = 1,#level_handlers do
+			level_handlers[i](source_name, level, message, ...);
+		end
+	end
+
+	return logger;
+end
+
+local function reset()
+	for level, handler_list in pairs(level_sinks) do
+		-- Clear all handlers for this level
+		for i = 1, #handler_list do
+			handler_list[i] = nil;
+		end
+	end
+end
+
+local function add_level_sink(level, sink_function)
+	if not level_sinks[level] then
+		level_sinks[level] = { sink_function };
+	else
+		level_sinks[level][#level_sinks[level] + 1 ] = sink_function;
+	end
+end
+
+local function add_simple_sink(simple_sink_function, levels)
+	local format = require "util.format".format;
+	local function sink_function(name, level, msg, ...)
+		return simple_sink_function(name, level, format(msg, ...));
+	end
+	for _, level in ipairs(levels or {"debug", "info", "warn", "error"}) do
+		add_level_sink(level, sink_function);
+	end
+end
+
+return {
+	init = init;
+	make_logger = make_logger;
+	reset = reset;
+	add_level_sink = add_level_sink;
+	add_simple_sink = add_simple_sink;
+	new = make_logger;
+};