FTP! Yay!

function read( _sReplaceChar, _tHistory )
	term.setCursorBlink( true )

    local sLine = ""
	local nHistoryPos = nil
	local nPos = 0
    if _sReplaceChar then
		_sReplaceChar = string.sub( _sReplaceChar, 1, 1 )
	end

	local w, h = term.getSize()
	local sx, sy = term.getCursorPos()

	local function redraw( _sCustomReplaceChar )
		local nScroll = 0
		if sx + nPos >= w then
			nScroll = (sx + nPos) - w
		end

		local tx,ty = term.getCursorPos()
		if ty ~= sy and nPos == 0 then sy = ty + (ty - sy) end

		term.setCursorPos( sx, sy )
		local sReplace = _sCustomReplaceChar or _sReplaceChar
		if sReplace then
			term.write( string.rep(sReplace, string.len(sLine) - nScroll) )
		else
			term.write( string.sub( sLine, nScroll + 1 ) )
		end
		term.setCursorPos( sx + nPos - nScroll, sy )
	end

	while true do
		local sEvent, param = os.pullEvent()
		if sEvent == "char" then
			sLine = string.sub( sLine, 1, nPos ) .. param .. string.sub( sLine, nPos + 1 )
			nPos = nPos + 1
			redraw()

		elseif sEvent == "key" then
		    if param == keys.enter then
				-- Enter
				break

			elseif param == keys.left then
				-- Left
				if nPos > 0 then
					nPos = nPos - 1
					redraw()
				end

			elseif param == keys.right then
				-- Right
				if nPos < string.len(sLine) then
					nPos = nPos + 1
					redraw()
				end

			elseif param == keys.up or param == keys.down then
                -- Up or down
				if _tHistory then
					redraw(" ");
					if param == keys.up then
						-- Up
						if nHistoryPos == nil then
							if #_tHistory > 0 then
								nHistoryPos = #_tHistory
							end
						elseif nHistoryPos > 1 then
							nHistoryPos = nHistoryPos - 1
						end
					else
						-- Down
						if nHistoryPos == #_tHistory then
							nHistoryPos = nil
						elseif nHistoryPos ~= nil then
							nHistoryPos = nHistoryPos + 1
						end
					end

					if nHistoryPos then
                    	sLine = _tHistory[nHistoryPos]
                    	nPos = string.len( sLine )
                    else
						sLine = ""
						nPos = 0
					end
					redraw()
                end
			elseif param == keys.backspace then
				-- Backspace
				if nPos > 0 then
					redraw(" ");
					sLine = string.sub( sLine, 1, nPos - 1 ) .. string.sub( sLine, nPos + 1 )
					nPos = nPos - 1
					redraw()
				end
			elseif param == keys.home then
				-- Home
				nPos = 0
				redraw()
			elseif param == keys.delete then
				if nPos < string.len(sLine) then
					redraw(" ");
					sLine = string.sub( sLine, 1, nPos ) .. string.sub( sLine, nPos + 2 )
					redraw()
				end
			elseif param == keys["end"] then
				-- End
				nPos = string.len(sLine)
				redraw()
			end
		end
	end

	term.setCursorBlink( false )
	term.setCursorPos( w + 1, sy )
	print()

	return sLine
end

local args={...}

local function log(s)
  local f = fs.open("ftp_log","a")
  f.writeLine(s)
  f.close()
  print(s)
end

for k,v in pairs(rs.getSides()) do
  if peripheral.getType(v) == "modem" then
    rednetSide = v
    break
  end
end

if not rednetSide then print("Rednet is needed!") return end

rednet.open(rednetSide)

local clients = {}

function auth(id,data)
  local u , pass = string.gmatch(data,"^(.-):(.+)$")()

  if pass == users[u] then
    log(u .. " connected with id ".. id)
    clients[id] = {user=u}
    return true
  else
    log("Attempt to log into " .. u .. " by id " .. id .. " failed!")
    return false
  end
end

function getDir(file)
  return string.gsub(file,fs.getName(file).."/","")
end

function getPerms(file)
  if string.find(file,"/") == nil then
    if perms[file] then
      return perms[fix(file)]
    else
      return {write="all",read="all"}
    end
  end

  if perms[fix(getDir(file))] then
    if perms[fix(file)] then
      return perms[fix(file)]
    else
      return perms[fix(getDir(file))]
    end
  else
    return {write="all",read="all"}
  end
end

function hasRead(file, user)
  local perms = getPerms(file).read
  if perms == "all" then
    return true
  elseif perms == "logged_in" then
    return user~=nil
  elseif type(perms) == "table" then
    for k,v in pairs(perms) do
      if user == v then return true end
    end
    return false
  end
end

function hasWrite(file, user)
  local perms = getPerms(file).write
  if perms == "all" then
    return true
  elseif perms == "logged_in" then
    return user~=nil
  elseif type(perms) == "table" then
    for k,v in pairs(perms) do
      if user == v then return true end
    end
    return false
  end
end

function put(id,data)
  local filename ,contents = string.gmatch(data,"^(.-):(.+)$")()

  local user
  if clients[id] then
    user=clients[id].user
  end
  if not hasWrite(filename,user) then
    local first = "User "
    if not user then
	     user = "An anonymous user"
      first = ""
	   end

    log(first .. user .. " tried to write forbidden file " ..filename)
    return false
  else
    local f = fs.open(filename,"w")
    f.write(contents)
    f.close()
    return true
  end
end

function get(id,data)
  local filename = data

  local user
  if clients[id] then
    user=clients[id].user
  end

  if not hasRead(filename,user) then
    local first = "User "
    if not user then
    	 user = "An anonymous user"
     	first = ""
    end
    log(first .. user .. " tried to read forbidden file ".. filename)
  else
    local f = fs.open(filename,"r")
    rednet.send(id,"DATA " .. filename .. ":" .. f.readAll())
    f.close()
  end
end

function list(id,data)
  local dir = data
  local s = ""

  if not hasRead(dir,user) then
    local first = "User "
    if not user then
      user = "An anonymous user"
      first = ""
    end
    log(first .. user .. " tried to list forbidden dir ".. dir)
  else
    for k,v in pairs(fs.list(data)) do
	  s = s .. v .. " "
    end
    rednet.send(id,"LIST " .. s)
  end
end

function host()
  while true do
    local clientID,msg = rednet.receive()
    print(clientID," ",msg)
    if msg:sub(1,7) == "CONNECT" then
      if auth(clientID,msg:sub(9)) then
        rednet.send(clientID,"ACCEPT")
      else
        rednet.send(clientID,"DENY")
      end
    elseif msg:sub(1,3) == "GET" then
      get(clientID,msg:sub(5))
    elseif msg:sub(1,3) == "PUT" then
      put(clientID,msg:sub(5))
    elseif msg:sub(1,4) == "QUIT" then
      clients[clientID] = nil
    elseif msg:sub(1,4) == "LIST" then
	  list(clientID,msg:sub(5))
    elseif msg:sub(1,2) == "CD" then
      if fs.exists(msg:sub(4)) or msg:sub(4) == "/" or msg:sub(4) == "" then
        rednet.send(clientID,"DIR " .. msg:sub(4))
      end
    end
  end
end

function client()
  while true do
    local serverID,msg = rednet.receive()

   if msg == "ACCEPT" then
     print("Connection accepted.")
   elseif msg == "DENY" then
      print("Permission denied.")
    elseif msg:sub(1,4) == "DATA" then
      local filename,content = string.gmatch(msg:sub(6),"^(.-):(.+)$")()
      local f = fs.open(filename,"w")
      f.write(content)
      f.close()
      print("Wrote " .. filename)
    elseif msg:sub(1,3) == "DIR" then
		curDir = msg:sub(5)
	elseif msg:sub(1,4) == "LIST" then
		print(msg:sub(6))
	end
  end
end

function readFile(name)
  local f = fs.open(name,"r")
  local r = f.readAll()
  f.close()
  return r
end

local curDir = ""

function toCmd(line)
  if string.lower(line:sub(1,3)) == "get" then
    return "GET " .. line:sub(5)
  elseif string.lower(line:sub(1,3)) == "put" then
    return "PUT " .. line:sub(5) .. ":" .. readFile(line:sub(5))
  elseif string.lower(line:sub(1,4)) == "list" then
	return "LIST " .. curDir
  elseif string.lower(line:sub(1,2)) == "cd" then
	curDir = line:sub(4)
  end
end

function input()
  while true do
    local line = read()
    local cmd=toCmd(line)
    if cmd then
      rednet.send(server,cmd)
    end
  end
end


if #args >= 1 then

  if args[1] == "host" then
    local f= fs.open("users","r")
    users = textutils.unserialize(f.readAll())
    f.close()

    f = fs.open("perms","r")
    perms = textutils.unserialize(f.readAll())
    f.close()

    host()
  else
    local id = tonumber(args[1])

    io.write("Username: ")
    local user = read()
    io.write("Password: ")
    local pass = read("*")
    rednet.send(id,"CONNECT "..user..":"..pass)

    parallel.waitForAny(client,input)
  end
else
  print("Usage: ftp host|<id>")
end

rednet.close(rednetSide)