--[[SPLIT MODULE ftp]]

--[[ A simple ftp server

 This is my implementation of a FTP server using Github user Neronix's
 example as inspriration, but as a cleaner Lua implementation that is
 suitable for use in LFS. The coding style adopted here is more similar to
 best practice for normal (PC) module implementations, as using LFS enables
 me to bias towards clarity of coding over brevity. It includes extra logic
 to handle some of the edge case issues more robustly. It also uses a
 standard forward reference coding pattern to allow the code to be laid out
 in main routine, subroutine order.

 The app will only call one FTP.open() or FTP.createServer() at any time,
 with any multiple calls requected, so FTP is a singleton static object.
 However there is nothing to stop multiple clients connecting to the FTP
 listener at the same time, and indeed some FTP clients do use multiple
 connections, so this server can accept and create multiple cxt objects.
 Each cxt object can also have a single DATA connection.

 Note that FTP also exposes a number of really private properties (which
 could be stores in local / upvals) as FTP properties for debug purposes.

 Note that this version has now been updated to allow the main methods to
 be optionally loaded lazily, and SPILT comments allow the source to be
 preprocessed for loading as either components in the "fast" Cmodule or as
 LC files in SPIFFS.
]]
--luacheck: read globals fast file net node tmr uart wifi FAST_ftp SPIFFS_ftp

local FTP, FTPindex = {client = {}}, nil

if FAST_ftp then
  function FTPindex(_, name) return fast.load('ftp-'..name) end
elseif SPIFFS_ftp then
  function FTPindex(_, name) return loadfile('ftp-'..name..'.lc') end
end

if FTPindex then return setmetatable(FTP,{__index=FTPindex}) end

function FTP.open(...)  --[[SPLIT HERE ftp-open]]
--------------------------- Set up the FTP object ----------------------------
--       FTP has three static methods: open, createServer and close
------------------------------------------------------------------------------

-- optional wrapper around createServer() which also starts the wifi session
-- Lua: FTP:open(user, pass, ssid, pwd[, dbgFlag])

local this, user, pass, ssid, pwd, dbgFlag = ...

  if ssid then
    wifi.setmode(wifi.STATION, false)
    wifi.sta.config { ssid = ssid, pwd  = pwd, save = false }
  end
  tmr.create():alarm(500, tmr.ALARM_AUTO, function(t) -- this: FTP, user, pass, dbgFlag
    if (wifi.sta.status() == wifi.STA_GOTIP) then
      t:unregister()
      print("Welcome to NodeMCU world", node.heap(), wifi.sta.getip())
      return this:createServer(user, pass, dbgFlag)
    else
      uart.write(0,".")
    end
  end)

end --[[SPLIT IGNORE]]
function FTP.createServer(...)  --[[SPLIT HERE ftp-createServer]]
-- Lua: FTP:createServer(user, pass[, dbgFlag])
  local this, user, pass, dbgFlag = ...
  local cnt = 0
  this.user, this.pass, dbgFlag = user, pass, (dbgFlag and true or false)

  this.debug = (not dbgFlag) and type -- executing type(...) is in effect a NOOP
             or function(fmt, ...) -- upval: cnt
                if (...) then fmt = fmt:format(...) end
                print(node.heap(),fmt)
                cnt = cnt + 1
                if cnt % 10 then tmr.wdclr() end
              end

  this.server = net.createServer(net.TCP, 180)
  _G.FTP = this
  this.debug("Server created: (userdata) %s", tostring(this.server))

  this.server:listen(21, function(sock) -- upval: this
      -- since a server can have multiple connections, each connection
      -- has its own CXN object (table) to store connection-wide globals.
      local CXN; CXN = {
        validUser = false,
        cmdSocket = sock,
        debug     = this.debug,
        FTP       = this,
        send      = function(rec, cb) -- upval: CXN
            CXN.debug("Sending: %s", rec)
            return CXN.cmdSocket:send(rec.."\r\n", cb)
          end, --- CXN. send()
        close    = function(socket)   -- upval: CXN
             CXN.debug("Closing CXN.cmdSocket=%s", tostring(CXN.cmdSocket))
            for _,s in ipairs{'cmdSocket', 'dataServer', 'dataSocket'} do
               CXN.debug("closing CXN.%s=%s", s, tostring(CXN[s]))
              if type(CXN[s])=='userdata' then
                pcall(socket.close, CXN[s])
                CXN[s]= nil
              end
            end
            CXN.FTP.client[socket] = nil
          end -- CXN.close()
        }

      local function validateUser(socket, data) -- upval: CXN
        -- validate the logon and if then switch to processing commands
         CXN.debug("Authorising: %s", data)
        local cmd, arg = data:match('([A-Za-z]+) *([^\r\n]*)')
        local msg =  "530 Not logged in, authorization required"
        cmd = cmd:upper()

        if   cmd == 'USER' then
          CXN.validUser = (arg == CXN.FTP.user)
          msg = CXN.validUser and
                 "331 OK. Password required" or
                 "530 user not found"

        elseif CXN.validUser and cmd == 'PASS' then
          if arg == CXN.FTP.pass then
            CXN.cwd = '/'
            socket:on("receive", function(soc, rec) -- upval: CXN
                assert(soc==CXN.cmdSocket)
                CXN.FTP.processCommand(CXN, rec)
              end) -- logged on so switch to command mode
            msg = "230 Login successful. Username & password correct; proceed."
          else
            msg = "530 Try again"
          end

        elseif cmd == 'AUTH' then
          msg = "500 AUTH not understood"
        end

        return CXN.send(msg)
      end

    local port,ip = sock:getpeer() -- luacheck: no unused
    --cxt.debug("Connection accepted: (userdata) %s client %s:%u", tostring(sock), ip, port)
    sock:on("receive",       validateUser)
    sock:on("disconnection", CXN.close)
    this.client[sock]=CXN

    CXN.send("220 FTP server ready");
  end) -- this.server:listen()
end --[[SPLIT IGNORE]]
function FTP.close(...)  --[[SPLIT HERE ftp-close]]
-- Lua: FTP:close()

local this = ...

  -- this.client is a table of soc = cnx.  The first (and usually only connection) is cleared
  -- immediately and next() used to do a post chain so we only close one client per task
  local function rollupClients(skt,cxt)  -- upval: this, rollupClients
    if skt then
      this.debug("Client close: %s", tostring(skt))
      cxt.close(skt)
      this.client[skt] = nil
      node.task.post(function() return rollupClients(next(this.client, skt)) end) -- upval: rollupClients, this, skt
    else -- we have emptied the open socket table, so can now shut the server
      this.debug("Server close: %s", tostring(this. server))
      this.server:close()
      this.server:__gc()
      _G.FTP = nil
    end
  end
  rollupClients(next(this.client))
  package.loaded.ftpserver = nil

end --[[SPLIT IGNORE]]
function FTP.processCommand(...)  --[[SPLIT HERE ftp-processCommand]]
----------------------------- Process Command --------------------------------
-- This splits the valid commands into one of three categories:
--   *  bare commands (which take no arg)
--   *  simple commands (which take) a single arg; and
--   *  data commands which initiate data transfer to or from the client and
--      hence need to use CBs.
--
-- Find strings are used do this lookup and minimise long if chains.
------------------------------------------------------------------------------

local cxt, data = ...

  cxt.debug("Command: %s", data)
  data = data:gsub('[\r\n]+$', '') -- chomp trailing CRLF
  local cmd, arg = data:match('([a-zA-Z]+) *(.*)')
  cmd = cmd:upper()
  local _cmd_ = '_'..cmd..'_'
  if ('_CDUP_NOOP_PASV_PWD_QUIT_SYST_'):find(_cmd_) then
    cxt.FTP.processBareCmds(cxt, cmd)
  elseif ('_CWD_DELE_MODE_PORT_RNFR_RNTO_SIZE_TYPE_'):find(_cmd_) then
    cxt.FTP.processSimpleCmds(cxt, cmd, arg)
  elseif ('_LIST_NLST_RETR_STOR_'):find(_cmd_) then
    cxt.FTP.processDataCmds(cxt, cmd, arg)
  else
    cxt.send("500 Unknown error")
  end

end --[[SPLIT IGNORE]]
function FTP.processBareCmds(...)  --[[SPLIT HERE ftp-processBareCmds]]
-------------------------- Process Bare Commands -----------------------------

local cxt, cmd = ...


  local send = cxt.send

  if cmd == 'CDUP' then
    return send("250 OK. Current directory is "..cxt.cwd)

  elseif cmd == 'NOOP' then
    return send("200 OK")

  elseif cmd == 'PASV' then
    -- This FTP implementation ONLY supports PASV mode, and the passive port
    -- listener is opened on receipt of the PASV command.  If any data xfer
    -- commands return an error if the PASV command hasn't been received.
    -- Note the listener service is closed on receipt of the next PASV or
    -- quit.
    local ip, port, pphi, pplo, i1, i2, i3, i4, _
    _,ip = cxt.cmdSocket:getaddr()
    port = 2121
    pplo = port % 256
    pphi = (port-pplo)/256
    i1,i2,i3,i4 = ip:match("(%d+).(%d+).(%d+).(%d+)")
    cxt.FTP.dataServer(cxt, port)
    return send(
       ('227 Entering Passive Mode(%d,%d,%d,%d,%d,%d)'):format(
         i1,i2,i3,i4,pphi,pplo))

  elseif cmd == 'PWD' then
    return send('257 "/" is the current directory')

  elseif cmd == 'QUIT' then
    send("221 Goodbye", function() cxt.close(cxt.cmdSocket) end) -- upval: cxt
    return

  elseif cmd == 'SYST' then
--  return send("215 UNKNOWN")
    return send("215 UNIX Type: L8") -- must be Unix so ls is parsed correctly

  else
    error('Oops.  Missed '..cmd)
  end

end --[[SPLIT IGNORE]]
function FTP.processSimpleCmds(...)  --[[SPLIT HERE ftp-processSimpleCmds]]

------------------------- Process Simple Commands ----------------------------

local cxt, cmd, arg = ...


  local send = cxt.send

  if cmd == 'MODE' then
    return send(arg == "S" and "200 S OK" or
                               "504 Only S(tream) is suported")

  elseif cmd == 'PORT' then
    cxt.FTP.dataServer(cxt,nil) -- clear down any PASV setting
    return send("502 Active mode not supported. PORT not implemented")

  elseif cmd == 'TYPE' then
    if arg == "A" then
      cxt.xferType = 0
      return send("200 TYPE is now ASII")
    elseif arg == "I" then
      cxt.xferType = 1
      return send("200 TYPE is now 8-bit binary")
    else
      return send("504 Unknown TYPE")
    end
  end

  -- The remaining commands take a filename as an arg. Strip off leading / and ./
  arg = arg:gsub('^%.?/',''):gsub('^%.?/','')
  cxt.debug("Filename is %s",arg)

  if cmd == 'CWD' then
    if arg:match('^[%./]*$') then
      return send("250 CWD command successful")
    end
    return send("550 "..arg..": No such file or directory")

  elseif cmd == 'DELE' then
    if file.exists(arg) then
      file.remove(arg)
      if not file.exists(arg) then return send("250 Deleted "..arg) end
    end
    return send("550 Requested action not taken")

  elseif cmd == 'RNFR' then
    cxt.from = arg
    send("350 RNFR accepted")
    return

  elseif cmd == 'RNTO' then
    local status = cxt.from and file.rename(cxt.from, arg)
    cxt.debug("rename('%s','%s')=%s", tostring(cxt.from), tostring(arg), tostring(status))
    cxt.from = nil
    return send(status and "250 File renamed" or
                            "550 Requested action not taken")
  elseif cmd == "SIZE" then
    local st = file.stat(arg)
    return send(st and ("213 "..st.size) or
                       "550 Could not get file size.")

  else
    error('Oops.  Missed '..cmd)
  end

end --[[SPLIT IGNORE]]
function FTP.processDataCmds(...)  --[[SPLIT HERE ftp-processDataCmds]]

-------------------------- Process Data Commands -----------------------------

local cxt, cmd, arg = ...


  local send, FTP = cxt.send, cxt.FTP -- luacheck: ignore FTP

  -- The data commands are only accepted if a PORT command is in scope
  if FTP.dataServer == nil and cxt.dataSocket == nil then
    return send("502 Active mode not supported. "..cmd.." not implemented")
  end

  cxt.getData, cxt.setData = nil, nil

  arg = arg:gsub('^%.?/',''):gsub('^%.?/','')

  if cmd == "LIST" or cmd == "NLST" then
    -- There are
    local fileSize, nameList, pattern = file.list(), {}, '.'

    arg = arg:gsub('^-[a-z]* *', '') -- ignore any Unix style command parameters
    arg = arg:gsub('^/','')  -- ignore any leading /

    if #arg > 0 and arg ~= '.' then -- replace "*" by [^/%.]* that is any string not including / or .
      pattern = arg:gsub('*','[^/%%.]*')
    end

    for k, _ in pairs(fileSize) do
      if k:match(pattern) then
        nameList[#nameList+1] = k
      else
        fileSize[k] = nil
      end
    end
    table.sort(nameList)

    function cxt.getData(c) -- upval: cmd, fileSize, nameList
      local list, user = {}, c.FTP.user
      for i = 1,10 do -- luacheck: no unused
        if #nameList == 0 then break end
        local f = table.remove(nameList, 1)
        list[#list+1] = (cmd == "LIST") and
          ("-rw-r--r-- 1 %s %s %6u Jan  1 00:00 %s\r\n"):format(user, user, fileSize[f], f) or
          (f.."\r\n")
      end
      return table.concat(list)
    end

  elseif cmd == "RETR" then
    local f = file.open(arg, "r")
    if f then -- define a getter to read the file
      function cxt.getData(c) -- luacheck: ignore c -- upval: f
        local buf = f:read(1024)
        if not buf then f:close(); f = nil; end
        return buf
      end -- cxt.getData()
    end

  elseif cmd == "STOR" then
    local f = file.open(arg, "w")
    if f then -- define a setter to write the file
      function cxt.setData(c, rec) -- luacheck: ignore c -- upval: f (, arg)
        cxt.debug("writing %u bytes to %s", #rec, arg)
        return f:write(rec)
      end -- cxt.saveData(rec)
      function cxt.fileClose(c) -- luacheck: ignore c -- upval: f (,arg)
        cxt.debug("closing %s", arg)
        f:close(); f = nil
      end -- cxt.close()
    end

  end

  send((cxt.getData or cxt.setData) and "150 Accepted data connection" or
                                        "451 Can't open/create "..arg)
  if cxt.getData and cxt.dataSocket then
    cxt.debug ("poking sender to initiate first xfer")
    node.task.post(function() cxt.sender(cxt.dataSocket) end)   -- upval: cxt
  end

end --[[SPLIT IGNORE]]
function FTP.dataServer(...)  --[[SPLIT HERE ftp-dataServer]]
----------------------------- Data Port Routines -----------------------------
-- These are used to manage the data transfer over the data port.  This is
-- set up lazily either by a PASV or by the first LIST NLST RETR or STOR
-- command that uses it.  These also provide a sendData / receiveData cb to
-- handle the actual xfer. Also note that the sending process can be primed in
--
----------------   Open a new data server and port ---------------------------

local cxt, n = ...

  local dataSvr = cxt.dataServer
  if dataSvr then pcall(dataSvr.close, dataSrv) end -- luacheck: ignore -- close any existing listener
  if n then
    -- Open a new listener if needed. Note that this is only used to establish
    -- a single connection, so ftpDataOpen closes the server socket
    dataSvr = net.createServer(net.TCP, 300)
    cxt.dataServer = dataSvr
    dataSvr:listen(n, function(sock) -- upval: cxt
      cxt.FTP.ftpDataOpen(cxt,sock)
      end)
    cxt.debug("Listening on Data port %u, server %s",n, tostring(cxt.dataServer))
  else
    cxt.dataServer = nil
    cxt.debug("Stopped listening on Data port",n)
  end

end --[[SPLIT IGNORE]]
function FTP.ftpDataOpen(...)  --[[SPLIT HERE ftp-ftpDataOpen]]
----------------------- Connection on FTP data port ------------------------

local cxt, dataSocket = ...

  local sport,sip = dataSocket:getaddr()
  local cport,cip = dataSocket:getpeer()
  cxt.debug("Opened data socket %s from %s:%u to %s:%u", tostring(dataSocket),sip,sport,cip,cport )
  cxt.dataSocket = dataSocket

  cxt.dataServer:close()
  cxt.dataServer = nil

  function cxt.cleardown(cxt, skt, cdtype)  --luacheck: ignore cxt -- shadowing
    -- luacheck: ignore cdtype which
    cdtype = cdtype==1 and "disconnection" or "reconnection"
    local which = cxt.setData and "setData" or (cxt.getData and cxt.getData or "neither")
    cxt.debug("Cleardown entered from %s with %s", cdtype, which)
    if cxt.setData then
      cxt:fileClose()
      cxt.setData = nil
      cxt.send("226 Transfer complete.")
    else
      cxt.getData, cxt.sender = nil, nil
    end
    cxt.debug("Clearing down data socket %s", tostring(skt))
    node.task.post(function() -- upval: cxt, skt
        pcall(skt.close, skt); skt=nil
        cxt.dataSocket = nil
      end)
  end

  local on_hold = false

  dataSocket:on("receive", function(skt, rec) -- upval: cxt, on_hold

    local rectype = cxt.setData and "setData" or (cxt.getData and cxt.getData or "neither")
    cxt.debug("Received %u data bytes with %s", #rec, rectype)

    if not cxt.setData then return end

    if not on_hold then
      -- Cludge to stop the client flooding the ESP SPIFFS on an upload of a
      -- large file. As soon as a record arrives assert a flow control hold.
      -- This can take up to 5 packets to come into effect at which point the
      -- low priority unhold task is executed releasing the flow again.
      cxt.debug("Issuing hold on data socket %s", tostring(skt))
      skt:hold(); on_hold = true
      node.task.post(node.task.LOW_PRIORITY,
           function() -- upval: skt, on_hold
             cxt.debug("Issuing unhold on data socket %s", tostring(skt))
             pcall(skt.unhold, skt); on_hold = false
           end)
    end

    if not cxt:setData(rec) then
      cxt.debug("Error writing to SPIFFS")
      cxt:fileClose()
      cxt.setData = nil
      cxt.send("552 Upload aborted. Exceeded storage allocation")
    end
  end)

  function cxt.sender(skt) -- upval: cxt
    cxt.debug ("entering sender")
    if not cxt.getData then return end
    skt = skt or cxt.dataSocket
    local rec = cxt:getData()
    if rec and #rec > 0 then
      cxt.debug("Sending %u data bytes", #rec)
      skt:send(rec)
    else
      cxt.debug("Send of data completed")
      skt:close()
      cxt.send("226 Transfer complete.")
      cxt.getData, cxt.dataSocket = nil, nil
    end
  end

  dataSocket:on("sent", cxt.sender)
  dataSocket:on("disconnection", function(skt) return cxt:cleardown(skt,1) end) -- upval: cxt
  dataSocket:on("reconnection",  function(skt) return cxt:cleardown(skt,2) end) -- upval: cxt

  -- if we are sending to client then kick off the first send
  if cxt.getData then cxt.sender(cxt.dataSocket) end

end --[[SPLIT HERE]]
return FTP --[[SPLIT IGNORE]]
