-- 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 indexedbheap = require "prosody.util.indexedbheap";

local log = require "prosody.util.logger".init("timer");

local server = require "prosody.net.server";

local get_time = require "prosody.util.time".now

local type = type;

local debug_traceback = debug.traceback;

local tostring = tostring;

local xpcall = require "prosody.util.xpcall".xpcall;

local math_max = math.max;

local pairs = pairs;

if server.timer then

	-- The selected net.server implements this API, so defer to that

	return server.timer;

end

local _ENV = nil;

-- luacheck: std none

local _add_task = server.add_task;

local _server_timer;

local _active_timers = 0;

local h = indexedbheap.create();

local params = {};

local next_time = nil;

local function _traceback_handler(err) log("error", "Traceback[timer]: %s", debug_traceback(tostring(err), 2)); end

local function _on_timer(now)

	local peek;

	local readd;

	while true do

		peek = h:peek();

		if peek == nil or peek > now then break; end

		local _, callback, id = h:pop();

		local param = params[id];

		params[id] = nil;

		--item(now, id, _param);

		local success, err = xpcall(callback, _traceback_handler, now, id, param);

		if success and type(err) == "number" then

			if readd then

				readd[id] = { callback, err + now };

			else

				readd = { [id] = { callback, err + now } };

			end

			params[id] = param;

		end

	end

	if readd then

		for id,timer in pairs(readd) do

			h:insert(timer[1], timer[2], id);

		end

		peek = h:peek();

	end

	if peek ~= nil and _active_timers > 1 and peek == next_time then

		-- Another instance of _on_timer already set next_time to the same value,

		-- so it should be safe to not renew this timer event

		peek = nil;

	else

		next_time = peek;

	end

	if peek then

		-- peek is the time of the next event

		return peek - now;

	end

	_active_timers = _active_timers - 1;

end

local function add_task(delay, callback, param)

	local current_time = get_time();

	local event_time = current_time + delay;

	local id = h:insert(callback, event_time);

	params[id] = param;

	if next_time == nil or event_time < next_time then

		next_time = event_time;

		if _server_timer then

			_server_timer:close();

			_server_timer = nil;

		else

			_active_timers = _active_timers + 1;

		end

		_server_timer = _add_task(next_time - current_time, _on_timer);

	end

	return id;

end

local function stop(id)

	params[id] = nil;

	local result, item, result_sync = h:remove(id);

	local peek = h:peek();

	if peek ~= next_time and _server_timer then

		next_time = peek;

		_server_timer:close();

		if next_time ~= nil then

			_server_timer = _add_task(math_max(next_time - get_time(), 0), _on_timer);

		end

	end

	return result, item, result_sync;

end

local function reschedule(id, delay)

	local current_time = get_time();

	local event_time = current_time + delay;

	h:reprioritize(id, delay);

	if next_time == nil or event_time < next_time then

		next_time = event_time;

		_add_task(next_time - current_time, _on_timer);

	end

	return id;

end

return {

	add_task = add_task;

	stop = stop;

	reschedule = reschedule;

};