--[[

        server.lua by blastbeat

        - this script contains the server loop of the program
        - other scripts can reg a server here

]]--

-- // wrapping luadch stuff // --

local use = function( what )
    return _G[ what ]
end
local clean = function( tbl )
    for i, k in pairs( tbl ) do
        tbl[ i ] = nil
    end
end

local log, table_concat = require ("util.logger").init("socket"), table.concat;
local out_put = function (...) return log("debug", table_concat{...}); end
local out_error = function (...) return log("warn", table_concat{...}); end
local mem_free = collectgarbage

----------------------------------// DECLARATION //--

--// constants //--

local STAT_UNIT = 1    -- byte

--// lua functions //--

local type = use "type"
local pairs = use "pairs"
local ipairs = use "ipairs"
local tostring = use "tostring"
local collectgarbage = use "collectgarbage"

--// lua libs //--

local os = use "os"
local table = use "table"
local string = use "string"
local coroutine = use "coroutine"

--// lua lib methods //--

local os_time = os.time
local os_difftime = os.difftime
local table_concat = table.concat
local table_remove = table.remove
local string_len = string.len
local string_sub = string.sub
local coroutine_wrap = coroutine.wrap
local coroutine_yield = coroutine.yield

--// extern libs //--

local luasec = select( 2, pcall( require, "ssl" ) )
local luasocket = require "socket"

--// extern lib methods //--

local ssl_wrap = ( luasec and luasec.wrap )
local socket_bind = luasocket.bind
local socket_sleep = luasocket.sleep
local socket_select = luasocket.select
local ssl_newcontext = ( luasec and luasec.newcontext )

--// functions //--

local id
local loop
local stats
local idfalse
local addtimer
local closeall
local addserver
local wrapserver
local getsettings
local closesocket
local removesocket
local removeserver
local changetimeout
local wrapconnection
local changesettings

--// tables //--

local _server
local _readlist
local _timerlist
local _sendlist
local _socketlist
local _closelist
local _readtimes
local _writetimes

--// simple data types //--

local _
local _readlistlen
local _sendlistlen
local _timerlistlen

local _sendtraffic
local _readtraffic

local _selecttimeout
local _sleeptime

local _starttime
local _currenttime

local _maxsendlen
local _maxreadlen

local _checkinterval
local _sendtimeout
local _readtimeout

local _cleanqueue

local _timer

local _maxclientsperserver

----------------------------------// DEFINITION //--

_server = { }    -- key = port, value = table; list of listening servers
_readlist = { }    -- array with sockets to read from
_sendlist = { }    -- arrary with sockets to write to
_timerlist = { }    -- array of timer functions
_socketlist = { }    -- key = socket, value = wrapped socket (handlers)
_readtimes = { }   -- key = handler, value = timestamp of last data reading
_writetimes = { }   -- key = handler, value = timestamp of last data writing/sending
_closelist = { }    -- handlers to close

_readlistlen = 0    -- length of readlist
_sendlistlen = 0    -- length of sendlist
_timerlistlen = 0    -- lenght of timerlist

_sendtraffic = 0    -- some stats
_readtraffic = 0

_selecttimeout = 1    -- timeout of socket.select
_sleeptime = 0    -- time to wait at the end of every loop

_maxsendlen = 51000 * 1024    -- max len of send buffer
_maxreadlen = 25000 * 1024    -- max len of read buffer

_checkinterval = 1200000    -- interval in secs to check idle clients
_sendtimeout = 60000    -- allowed send idle time in secs
_readtimeout = 6 * 60 * 60    -- allowed read idle time in secs

_cleanqueue = false    -- clean bufferqueue after using

_maxclientsperserver = 1000

----------------------------------// PRIVATE //--

wrapserver = function( listeners, socket, ip, serverport, pattern, sslctx, maxconnections, startssl )    -- this function wraps a server

    maxconnections = maxconnections or _maxclientsperserver

    local connections = 0

    local dispatch, disconnect = listeners.incoming or listeners.listener, listeners.disconnect

    local err

    local ssl = false

    if sslctx then
        if not ssl_newcontext then
            return nil, "luasec not found"
        end
        if type( sslctx ) ~= "table" then
            out_error "server.lua: wrong server sslctx"
            return nil, "wrong server sslctx"
        end
        sslctx, err = ssl_newcontext( sslctx )
        if not sslctx then
            err = err or "wrong sslctx parameters"
            out_error( "server.lua: ", err )
            return nil, err
        end
        ssl = true
    else
	out_put("server.lua: ", "ssl not enabled on ", serverport);
    end

    local accept = socket.accept

    --// public methods of the object //--

    local handler = { }

    handler.shutdown = function( ) end

    handler.ssl = function( )
        return ssl
    end
    handler.remove = function( )
        connections = connections - 1
    end
    handler.close = function( )
        for _, handler in pairs( _socketlist ) do
            if handler.serverport == serverport then
                handler.disconnect( handler, "server closed" )
                handler.close( true )
            end
        end
        socket:close( )
        _sendlistlen = removesocket( _sendlist, socket, _sendlistlen )
        _readlistlen = removesocket( _readlist, socket, _readlistlen )
        _socketlist[ socket ] = nil
        handler = nil
        socket = nil
        mem_free( )
        out_put "server.lua: closed server handler and removed sockets from list"
    end
    handler.ip = function( )
        return ip
    end
    handler.serverport = function( )
        return serverport
    end
    handler.socket = function( )
        return socket
    end
    handler.readbuffer = function( )
        if connections > maxconnections then
            out_put( "server.lua: refused new client connection: server full" )
            return false
        end
        local client, err = accept( socket )    -- try to accept
        if client then
            local ip, clientport = client:getpeername( )
            client:settimeout( 0 )
            local handler, client, err = wrapconnection( handler, listeners, client, ip, serverport, clientport, pattern, sslctx, startssl )    -- wrap new client socket
            if err then    -- error while wrapping ssl socket
                return false
            end
            connections = connections + 1
            out_put( "server.lua: accepted new client connection from ", ip, ":", clientport, " to ",  serverport)
            return dispatch( handler )
        elseif err then    -- maybe timeout or something else
            out_put( "server.lua: error with new client connection: ", err )
            return false
        end
    end
    return handler
end

wrapconnection = function( server, listeners, socket, ip, serverport, clientport, pattern, sslctx, startssl )    -- this function wraps a client to a handler object

    socket:settimeout( 0 )

    --// local import of socket methods //--

    local send
    local receive
    local shutdown

    --// private closures of the object //--

    local ssl

    local dispatch = listeners.incoming or listeners.listener
    local disconnect = listeners.disconnect

    local bufferqueue = { }    -- buffer array
    local bufferqueuelen = 0    -- end of buffer array

    local toclose
    local fatalerror
    local needtls

    local bufferlen = 0

    local noread = false
    local nosend = false

    local sendtraffic, readtraffic = 0, 0

    local maxsendlen = _maxsendlen
    local maxreadlen = _maxreadlen

    --// public methods of the object //--

    local handler = bufferqueue    -- saves a table ^_^

    handler.dispatch = function( )
        return dispatch
    end
    handler.disconnect = function( )
        return disconnect
    end
    handler.setlistener = function( listeners )
        dispatch = listeners.incoming
        disconnect = listeners.disconnect
    end
    handler.getstats = function( )
        return readtraffic, sendtraffic
    end
    handler.ssl = function( )
        return ssl
    end
    handler.send = function( _, data, i, j )
        return send( socket, data, i, j )
    end
    handler.receive = function( pattern, prefix )
        return receive( socket, pattern, prefix )
    end
    handler.shutdown = function( pattern )
        return shutdown( socket, pattern )
    end
    handler.close = function( forced )
        if not handler then return true; end
        _readlistlen = removesocket( _readlist, socket, _readlistlen )
        _readtimes[ handler ] = nil
        if bufferqueuelen ~= 0 then
            if not ( forced or fatalerror ) then
                handler.sendbuffer( )
                if bufferqueuelen ~= 0 then   -- try again...
                    handler.write = nil    -- ... but no further writing allowed
                    toclose = true
                    return false
                end
            else
                send( socket, table_concat( bufferqueue, "", 1, bufferqueuelen ), 1, bufferlen )    -- forced send
            end
        end
        _ = shutdown and shutdown( socket )
        socket:close( )
        _sendlistlen = removesocket( _sendlist, socket, _sendlistlen )
        _socketlist[ socket ] = nil
        _writetimes[ handler ] = nil
        _closelist[ handler ] = nil
        handler = nil
        socket = nil
        mem_free( )
	if server then
		server.remove( )
	end
        out_put "server.lua: closed client handler and removed socket from list"
        return true
    end
    handler.ip = function( )
        return ip
    end
    handler.serverport = function( )
        return serverport
    end
    handler.clientport = function( )
        return clientport
    end
    local write = function( data )
        bufferlen = bufferlen + string_len( data )
        if bufferlen > maxsendlen then
            _closelist[ handler ] = "send buffer exceeded"   -- cannot close the client at the moment, have to wait to the end of the cycle
            handler.write = idfalse    -- dont write anymore
            return false
        elseif socket and not _sendlist[ socket ] then
            _sendlistlen = _sendlistlen + 1
            _sendlist[ _sendlistlen ] = socket
            _sendlist[ socket ] = _sendlistlen
        end
        bufferqueuelen = bufferqueuelen + 1
        bufferqueue[ bufferqueuelen ] = data
        if handler then
        	_writetimes[ handler ] = _writetimes[ handler ] or _currenttime
        end
        return true
    end
    handler.write = write
    handler.bufferqueue = function( )
        return bufferqueue
    end
    handler.socket = function( )
        return socket
    end
    handler.pattern = function( new )
        pattern = new or pattern
        return pattern
    end
    handler.bufferlen = function( readlen, sendlen )
        maxsendlen = sendlen or maxsendlen
        maxreadlen = readlen or maxreadlen
        return maxreadlen, maxsendlen
    end
    handler.lock = function( switch )
        if switch == true then
            handler.write = idfalse
            local tmp = _sendlistlen
            _sendlistlen = removesocket( _sendlist, socket, _sendlistlen )
            _writetimes[ handler ] = nil
            if _sendlistlen ~= tmp then
                nosend = true
            end
            tmp = _readlistlen
            _readlistlen = removesocket( _readlist, socket, _readlistlen )
            _readtimes[ handler ] = nil
            if _readlistlen ~= tmp then
                noread = true
            end
        elseif switch == false then
            handler.write = write
            if noread then
                noread = false
                _readlistlen = _readlistlen + 1
                _readlist[ socket ] = _readlistlen
                _readlist[ _readlistlen ] = socket
                _readtimes[ handler ] = _currenttime
            end
            if nosend then
                nosend = false
                write( "" )
            end
        end
        return noread, nosend
    end
    local _readbuffer = function( )    -- this function reads data
        local buffer, err, part = receive( socket, pattern )    -- receive buffer with "pattern"
        if not err or ( err == "timeout" or err == "wantread" ) then    -- received something
            local buffer = buffer or part or ""
            local len = string_len( buffer )
            if len > maxreadlen then
                disconnect( handler, "receive buffer exceeded" )
                handler.close( true )
                return false
            end
            local count = len * STAT_UNIT
            readtraffic = readtraffic + count
            _readtraffic = _readtraffic + count
            _readtimes[ handler ] = _currenttime
            --out_put( "server.lua: read data '", buffer, "', error: ", err )
            return dispatch( handler, buffer, err )
        else    -- connections was closed or fatal error
            out_put( "server.lua: client ", ip, ":", tostring(clientport), " error: ", tostring(err) )
            fatalerror = true
            disconnect( handler, err )
	    _ = handler and handler.close( )
            return false
        end
    end
    local _sendbuffer = function( )    -- this function sends data
        local buffer = table_concat( bufferqueue, "", 1, bufferqueuelen )
        local succ, err, byte = send( socket, buffer, 1, bufferlen )
        local count = ( succ or byte or 0 ) * STAT_UNIT
        sendtraffic = sendtraffic + count
        _sendtraffic = _sendtraffic + count
        _ = _cleanqueue and clean( bufferqueue )
        --out_put( "server.lua: sended '", buffer, "', bytes: ", succ, ", error: ", err, ", part: ", byte, ", to: ", ip, ":", clientport )
        if succ then    -- sending succesful
            bufferqueuelen = 0
            bufferlen = 0
            _sendlistlen = removesocket( _sendlist, socket, _sendlistlen )    -- delete socket from writelist
            _ = needtls and handler.starttls(true)
            _writetimes[ handler ] = nil
	    _ = toclose and handler.close( )
            return true
        elseif byte and ( err == "timeout" or err == "wantwrite" ) then    -- want write
            buffer = string_sub( buffer, byte + 1, bufferlen )    -- new buffer
            bufferqueue[ 1 ] = buffer    -- insert new buffer in queue
            bufferqueuelen = 1
            bufferlen = bufferlen - byte
            _writetimes[ handler ] = _currenttime
            return true
        else    -- connection was closed during sending or fatal error
            out_put( "server.lua: client ", ip, ":", clientport, " error: ", err )
            fatalerror = true
            disconnect( handler, err )
            _ = handler and handler.close( )
            return false
        end
    end

    if sslctx then    -- ssl?
        ssl = true
        local wrote
        local read
        local handshake = coroutine_wrap( function( client )    -- create handshake coroutine
                local err
                for i = 1, 10 do    -- 10 handshake attemps
                    _sendlistlen = ( wrote and removesocket( _sendlist, socket, _sendlistlen ) ) or _sendlistlen
                    _readlistlen = ( read and removesocket( _readlist, socket, _readlistlen ) ) or _readlistlen
                    read, wrote = nil, nil
                    _, err = client:dohandshake( )
                    if not err then
                        out_put( "server.lua: ssl handshake done" )
                        handler.readbuffer = _readbuffer    -- when handshake is done, replace the handshake function with regular functions
                        handler.sendbuffer = _sendbuffer
                        -- return dispatch( handler )
                        return true
                    else
                        out_put( "server.lua: error during ssl handshake: ", err )
                        if err == "wantwrite" and not wrote then
                            _sendlistlen = _sendlistlen + 1
                            _sendlist[ _sendlistlen ] = client
                            wrote = true
                        elseif err == "wantread" and not read then
                                _readlistlen = _readlistlen + 1
                                _readlist [ _readlistlen ] = client
                                read = true
                        else
                        	break;
                        end
                        --coroutine_yield( handler, nil, err )    -- handshake not finished
                        coroutine_yield( )
                    end
                end
                disconnect( handler, "ssl handshake failed" )
                handler.close( true )    -- forced disconnect
                return false    -- handshake failed
            end
        )
        if startssl then    -- ssl now?
            --out_put("server.lua: ", "starting ssl handshake")
	    local err
            socket, err = ssl_wrap( socket, sslctx )    -- wrap socket
            if err then
                out_put( "server.lua: ssl error: ", err )
                mem_free( )
                return nil, nil, err    -- fatal error
            end
            socket:settimeout( 0 )
            handler.readbuffer = handshake
            handler.sendbuffer = handshake
            handshake( socket )    -- do handshake
        else
            handler.starttls = function( now )
                if not now then
                    --out_put "server.lua: we need to do tls, but delaying until later"
                    needtls = true
                    return
                end
                --out_put( "server.lua: attempting to start tls on " .. tostring( socket ) )
                local oldsocket, err = socket
                socket, err = ssl_wrap( socket, sslctx )    -- wrap socket
                --out_put( "server.lua: sslwrapped socket is " .. tostring( socket ) )
                if err then
                    out_put( "server.lua: error while starting tls on client: ", err )
                    return nil, err    -- fatal error
                end

                socket:settimeout( 0 )

                -- add the new socket to our system

                send = socket.send
                receive = socket.receive
                shutdown = id

                _socketlist[ socket ] = handler
                _readlistlen = _readlistlen + 1
                _readlist[ _readlistlen ] = socket
                _readlist[ socket ] = _readlistlen

                -- remove traces of the old socket

                _readlistlen = removesocket( _readlist, oldsocket, _readlistlen )
                _sendlistlen = removesocket( _sendlist, oldsocket, _sendlistlen )
                _socketlist[ oldsocket ] = nil

                handler.starttls = nil
                needtls = nil

                handler.readbuffer = handshake
                handler.sendbuffer = handshake
                handshake( socket )    -- do handshake
            end
            handler.readbuffer = _readbuffer
            handler.sendbuffer = _sendbuffer
        end
    else    -- normal connection
        ssl = false
        handler.readbuffer = _readbuffer
        handler.sendbuffer = _sendbuffer
    end

    send = socket.send
    receive = socket.receive
    shutdown = ( ssl and id ) or socket.shutdown

    _socketlist[ socket ] = handler
    _readlistlen = _readlistlen + 1
    _readlist[ _readlistlen ] = socket
    _readlist[ socket ] = _readlistlen

    return handler, socket
end

id = function( )
end

idfalse = function( )
    return false
end

removesocket = function( list, socket, len )    -- this function removes sockets from a list ( copied from copas )
    local pos = list[ socket ]
    if pos then
        list[ socket ] = nil
        local last = list[ len ]
        list[ len ] = nil
        if last ~= socket then
            list[ last ] = pos
            list[ pos ] = last
        end
        return len - 1
    end
    return len
end

closesocket = function( socket )
    _sendlistlen = removesocket( _sendlist, socket, _sendlistlen )
    _readlistlen = removesocket( _readlist, socket, _readlistlen )
    _socketlist[ socket ] = nil
    socket:close( )
    mem_free( )
end

----------------------------------// PUBLIC //--

addserver = function( listeners, port, addr, pattern, sslctx, maxconnections, startssl )    -- this function provides a way for other scripts to reg a server
    local err
    --out_put("server.lua: autossl on ", port, " is ", startssl)
    if type( listeners ) ~= "table" then
        err = "invalid listener table"
    end
    if not type( port ) == "number" or not ( port >= 0 and port <= 65535 ) then
        err = "invalid port"
    elseif _server[ port ] then
        err =  "listeners on port '" .. port .. "' already exist"
    elseif sslctx and not luasec then
        err = "luasec not found"
    end
    if err then
        out_error( "server.lua: ", err )
        return nil, err
    end
    addr = addr or "*"
    local server, err = socket_bind( addr, port )
    if err then
        out_error( "server.lua: ", err )
        return nil, err
    end
    local handler, err = wrapserver( listeners, server, addr, port, pattern, sslctx, maxconnections, startssl )    -- wrap new server socket
    if not handler then
        server:close( )
        return nil, err
    end
    server:settimeout( 0 )
    _readlistlen = _readlistlen + 1
    _readlist[ _readlistlen ] = server
    _server[ port ] = handler
    _socketlist[ server ] = handler
    out_put( "server.lua: new server listener on '", addr, ":", port, "'" )
    return handler
end

removeserver = function( port )
    local handler = _server[ port ]
    if not handler then
        return nil, "no server found on port '" .. tostring( port ) "'"
    end
    handler.close( )
    return true
end

closeall = function( )
    for _, handler in pairs( _socketlist ) do
        handler.close( )
        _socketlist[ _ ] = nil
    end
    _readlistlen = 0
    _sendlistlen = 0
    _timerlistlen = 0
    _server = { }
    _readlist = { }
    _sendlist = { }
    _timerlist = { }
    _socketlist = { }
    mem_free( )
end

getsettings = function( )
    return  _selecttimeout, _sleeptime, _maxsendlen, _maxreadlen, _checkinterval, _sendtimeout, _readtimeout, _cleanqueue, _maxclientsperserver
end

changesettings = function( new )
    if type( new ) ~= "table" then
        return nil, "invalid settings table"
    end
    _selecttimeout = tonumber( new.timeout ) or _selecttimeout
    _sleeptime = tonumber( new.sleeptime ) or _sleeptime
    _maxsendlen = tonumber( new.maxsendlen ) or _maxsendlen
    _maxreadlen = tonumber( new.maxreadlen ) or _maxreadlen
    _checkinterval = tonumber( new.checkinterval ) or _checkinterval
    _sendtimeout = tonumber( new.sendtimeout ) or _sendtimeout
    _readtimeout = tonumber( new.readtimeout ) or _readtimeout
    _cleanqueue = new.cleanqueue
    _maxclientsperserver = new._maxclientsperserver or _maxclientsperserver
    return true
end

addtimer = function( listener )
    if type( listener ) ~= "function" then
        return nil, "invalid listener function"
    end
    _timerlistlen = _timerlistlen + 1
    _timerlist[ _timerlistlen ] = listener
    return true
end

stats = function( )
    return _readtraffic, _sendtraffic, _readlistlen, _sendlistlen, _timerlistlen
end

loop = function( )    -- this is the main loop of the program
    while true do
        local read, write, err = socket_select( _readlist, _sendlist, _selecttimeout )
        for i, socket in ipairs( write ) do    -- send data waiting in writequeues
            local handler = _socketlist[ socket ]
            if handler then
                handler.sendbuffer( )
            else
                closesocket( socket )
                out_put "server.lua: found no handler and closed socket (writelist)"    -- this should not happen
            end
        end
        for i, socket in ipairs( read ) do    -- receive data
            local handler = _socketlist[ socket ]
            if handler then
                handler.readbuffer( )
            else
                closesocket( socket )
                out_put "server.lua: found no handler and closed socket (readlist)"    -- this can happen
            end
        end
        for handler, err in pairs( _closelist ) do
            handler.disconnect( )( handler, err )
            handler.close( true )    -- forced disconnect
        end
        clean( _closelist )
        _currenttime = os_time( )
        if os_difftime( _currenttime - _timer ) >= 1 then
            for i = 1, _timerlistlen do
                _timerlist[ i ]( )    -- fire timers
            end
            _timer = _currenttime
        end
        socket_sleep( _sleeptime )    -- wait some time
        --collectgarbage( )
    end
end

--// EXPERIMENTAL //--

local wrapclient = function( socket, ip, serverport, listeners, pattern, sslctx, startssl )
    local handler = wrapconnection( nil, listeners, socket, ip, serverport, "clientport", pattern, sslctx, startssl )
    _socketlist[ socket ] = handler
    _sendlistlen = _sendlistlen + 1
    _sendlist[ _sendlistlen ] = socket
    _sendlist[ socket ] = _sendlistlen
    return handler, socket
end

local addclient = function( address, port, listeners, pattern, sslctx, startssl )
    local client, err = socket.tcp( )
    if err then
        return nil, err
    end
    client:settimeout( 0 )
    _, err = client:connect( address, port )
    if err then    -- try again
        local handler = wrapclient( client, address, port, listeners )
    else
        wrapconnection( server, listeners, socket, address, port, "clientport", pattern, sslctx, startssl )
    end
end

--// EXPERIMENTAL //--

----------------------------------// BEGIN //--

use "setmetatable" ( _socketlist, { __mode = "k" } )
use "setmetatable" ( _readtimes, { __mode = "k" } )
use "setmetatable" ( _writetimes, { __mode = "k" } )

_timer = os_time( )
_starttime = os_time( )

addtimer( function( )
        local difftime = os_difftime( _currenttime - _starttime )
        if difftime > _checkinterval then
            _starttime = _currenttime
            for handler, timestamp in pairs( _writetimes ) do
                if os_difftime( _currenttime - timestamp ) > _sendtimeout then
                    --_writetimes[ handler ] = nil
                    handler.disconnect( )( handler, "send timeout" )
                    handler.close( true )    -- forced disconnect
                end
            end
            for handler, timestamp in pairs( _readtimes ) do
                if os_difftime( _currenttime - timestamp ) > _readtimeout then
                    --_readtimes[ handler ] = nil
                    handler.disconnect( )( handler, "read timeout" )
                    handler.close( )    -- forced disconnect?
                end
            end
        end
    end
)

----------------------------------// PUBLIC INTERFACE //--

return {

    addclient = addclient,
    wrapclient = wrapclient,
    
    loop = loop,
    stats = stats,
    closeall = closeall,
    addtimer = addtimer,
    addserver = addserver,
    getsettings = getsettings,
    removeserver = removeserver,
    changesettings = changesettings,

}
