-- Prosody IM

-- Copyright (C) 2016 Kim Alvefur

--

-- This project is MIT/X11 licensed. Please see the

-- COPYING file in the source package for more information.

--

-- server_epoll

--  Server backend based on https://luarocks.org/modules/zash/lua-epoll

local t_sort = table.sort;

local t_insert = table.insert;

local t_remove = table.remove;

local t_concat = table.concat;

local setmetatable = setmetatable;

local tostring = tostring;

local pcall = pcall;

local pairs = pairs;

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

local epoll = require "epoll";

local socket = require "socket";

local luasec = require "ssl";

local gettime = require "util.time".now;

local createtable = require "util.table".create;

local _SOCKETINVALID = socket._SOCKETINVALID or -1;

assert(socket.tcp6 and socket.tcp4, "Incompatible LuaSocket version");

local _ENV = nil;

local default_config = { __index = {

	read_timeout = 900;

	write_timeout = 7;

	tcp_backlog = 128;

	accept_retry_interval = 10;

	read_retry_delay = 1e-06;

	connect_timeout = 20;

	handshake_timeout = 60;

	max_wait = 86400;

	min_wait = 1e-06;

}};

local cfg = default_config.__index;

local fds = createtable(10, 0); -- FD -> conn

-- Timer and scheduling --

local timers = {};

local function noop() end

local function closetimer(t)

	t[1] = 0;

	t[2] = noop;

end

-- Set to true when timers have changed

local resort_timers = false;

-- Add absolute timer

local function at(time, f)

	local timer = { time, f, close = closetimer };

	t_insert(timers, timer);

	resort_timers = true;

	return timer;

end

-- Add relative timer

local function addtimer(timeout, f)

	return at(gettime() + timeout, f);

end

-- Run callbacks of expired timers

-- Return time until next timeout

local function runtimers(next_delay, min_wait)

	-- Any timers at all?

	if not timers[1] then

		return next_delay;

	end

	if resort_timers then

		-- Sort earliest timers to the end

		t_sort(timers, function (a, b) return a[1] > b[1]; end);

		resort_timers = false;

	end

	-- Iterate from the end and remove completed timers

	for i = #timers, 1, -1 do

		local timer = timers[i];

		local t, f = timer[1], timer[2];

		-- Get time for every iteration to increase accuracy

		local now = gettime();

		if t > now then

			-- This timer should not fire yet

			local diff = t - now;

			if diff < next_delay then

				next_delay = diff;

			end

			break;

		end

		local new_timeout = f(now);

		if new_timeout then

			-- Schedule for 'delay' from the time actually scheduled,

			-- not from now, in order to prevent timer drift.

			timer[1] = t + new_timeout;

			resort_timers = true;

		else

			t_remove(timers, i);

		end

	end

	if resort_timers or next_delay < min_wait then

		-- Timers may be added from within a timer callback.

		-- Those would not be considered for next_delay,

		-- and we might sleep for too long, so instead

		-- we return a shorter timeout so we can

		-- properly sort all new timers.

		next_delay = min_wait;

	end

	return next_delay;

end

-- Socket handler interface

local interface = {};

local interface_mt = { __index = interface };

function interface_mt:__tostring()

	if self.sockname and self.peername then

		return ("FD %d (%s, %d, %s, %d)"):format(self:getfd(), self.peername, self.peerport, self.sockname, self.sockport);

	elseif self.sockname or self.peername then

		return ("FD %d (%s, %d)"):format(self:getfd(), self.sockname or self.peername, self.sockport or self.peerport);

	end

	return ("%s FD %d"):format(tostring(self.conn), self:getfd());

end

-- Replace the listener and tell the old one

function interface:setlistener(listeners)

	self:on("detach");

	self.listeners = listeners;

end

-- Call a listener callback

function interface:on(what, ...)

	local listener = self.listeners["on"..what];

	if not listener then

		-- log("debug", "Missing listener 'on%s'", what); -- uncomment for development and debugging

		return;

	end

	local ok, err = pcall(listener, self, ...);

	if not ok then

		log("error", "Error calling on%s: %s", what, err);

	end

	return err;

end

-- Return the file descriptor number

function interface:getfd()

	if self.conn then

		return self.conn:getfd();

	end

	return _SOCKETINVALID;

end

-- Get IP address

function interface:ip()

	return self.peername or self.sockname;

end

-- Get a port number, doesn't matter which

function interface:port()

	return self.sockport or self.peerport;

end

-- Get local port number

function interface:clientport()

	return self.sockport;

end

-- Get remote port

function interface:serverport()

	if self.sockport then

		return self.sockport;

	elseif self.server then

		self.server:port();

	end

end

-- Return underlying socket

function interface:socket()

	return self.conn;

end

function interface:setoption(k, v)

	-- LuaSec doesn't expose setoption :(

	if self.conn.setoption then

		self.conn:setoption(k, v);

	end

end

-- Timeout for detecting dead or idle sockets

function interface:setreadtimeout(t)

	if t == false then

		if self._readtimeout then

			self._readtimeout:close();

			self._readtimeout = nil;

		end

		return

	end

	t = t or cfg.read_timeout;

	if self._readtimeout then

		self._readtimeout[1] = gettime() + t;

		resort_timers = true;

	else

		self._readtimeout = addtimer(t, function ()

			if self:on("readtimeout") then

				return cfg.read_timeout;

			else

				self:on("disconnect", "read timeout");

				self:destroy();

			end

		end);

	end

end

-- Timeout for detecting dead sockets

function interface:setwritetimeout(t)

	if t == false then

		if self._writetimeout then

			self._writetimeout:close();

			self._writetimeout = nil;

		end

		return

	end

	t = t or cfg.write_timeout;

	if self._writetimeout then

		self._writetimeout[1] = gettime() + t;

		resort_timers = true;

	else

		self._writetimeout = addtimer(t, function ()

			self:on("disconnect", "write timeout");

			self:destroy();

		end);

	end

end

-- lua-epoll flag for currently requested poll state

function interface:flags()

	if self._wantread then

		if self._wantwrite then

			return "rw";

		end

		return "r";

	elseif self._wantwrite then

		return "w";

	end

end

-- Add or remove sockets or modify epoll flags

function interface:setflags(r, w)

	if r ~= nil then self._wantread = r; end

	if w ~= nil then self._wantwrite = w; end

	local flags = self:flags();

	local currentflags = self._flags;

	if flags == currentflags then

		return true;

	end

	local fd = self:getfd();

	if fd < 0 then

		self._wantread, self._wantwrite = nil, nil;

		return nil, "invalid fd";

	end

	local op = "mod";

	if not flags then

		op = "del";

	elseif not currentflags then

		op = "add";

	end

	local ok, err = epoll.ctl(op, fd, flags);

--	log("debug", "epoll_ctl(%q, %d, %q) -> %s" .. (err and ", %q" or ""),

--		op, fd, flags or "", tostring(ok), err);

	if not ok then return ok, err end

	if op == "add" then

		fds[fd] = self;

	elseif op == "del" then

		fds[fd] = nil;

	end

	self._flags = flags;

	return true;

end

-- Called when socket is readable

function interface:onreadable()

	local data, err, partial = self.conn:receive(self._pattern);

	if data then

		self:on("incoming", data);

	else

		if partial then

			self:on("incoming", partial, err);

		end

		if err == "wantread" then

			self:setflags(true, nil);

		elseif err == "wantwrite" then

			self:setflags(nil, true);

		elseif err ~= "timeout" then

			self:on("disconnect", err);

			self:destroy()

			return;

		end

	end

	if not self.conn then return; end

	if self.conn:dirty() then

		self:setreadtimeout(false);

		self:pausefor(cfg.read_retry_delay);

	else

		self:setreadtimeout();

	end

end

-- Called when socket is writable

function interface:onwriteable()

	local buffer = self.writebuffer;

	local data = t_concat(buffer);

	local ok, err, partial = self.conn:send(data);

	if ok then

		for i = #buffer, 1, -1 do

			buffer[i] = nil;

		end

		self:setflags(nil, false);

		self:setwritetimeout(false);

		self:ondrain(); -- Be aware of writes in ondrain

		return;

	end

	if partial then

		buffer[1] = data:sub(partial+1);

		for i = #buffer, 2, -1 do

			buffer[i] = nil;

		end

		self:setwritetimeout();

	end

	if err == "wantwrite" or err == "timeout" then

		self:setflags(nil, true);

	elseif err == "wantread" then

		self:setflags(true, nil);

	elseif err ~= "timeout" then

		self:on("disconnect", err);

		self:destroy();

	end

end

-- The write buffer has been successfully emptied

function interface:ondrain()

	if self._toclose then

		return self:close();

	elseif self._starttls then

		return self:starttls();

	else

		return self:on("drain");

	end

end

-- Add data to write buffer and set flag for wanting to write

function interface:write(data)

	local buffer = self.writebuffer;

	if buffer then

		t_insert(buffer, data);

	else

		self.writebuffer = { data };

	end

	self:setwritetimeout();

	self:setflags(nil, true);

	return #data;

end

interface.send = interface.write;

-- Close, possibly after writing is done

function interface:close()

	if self._wantwrite then

		self:setflags(false, true); -- Flush final buffer contents

		self.write, self.send = noop, noop; -- No more writing

		log("debug", "Close %s after writing", tostring(self));

		self._toclose = true;

	else

		log("debug", "Close %s now", tostring(self));

		self.write, self.send = noop, noop;

		self.close = noop;

		self:on("disconnect");

		self:destroy();

	end

end

function interface:destroy()

	self:setflags(false, false);

	self:setwritetimeout(false);

	self:setreadtimeout(false);

	self.onreadable = noop;

	self.onwriteable = noop;