local ftp_client = [[
-- socket_client class(client)
local socket_client = {
    _modem         = false;
    _channel       = 0;
    _reply_channel = 0;
    _side          = "top";
    _stack         = {};
}
socket_client.__index = socket_client

socket_client.__call = function(self, ch, rep_ch)
    local sides = {
        "right", "left",
        "top", "bottom",
        "front", "back"
    }

    local m = nil
    local side = "none"
    for k, v in ipairs(sides) do
        if peripheral.getType(v) == "modem" then
            side = v
            break
        end
    end

    if side == "none" then
        return -1
    end

    m = peripheral.wrap(side)

    local t = {
        _channel = ch;
        _reply_channel = rep_ch;
        _side    = s or "top";
        _modem   = m;
    }
    setmetatable(t, socket_client)

    return t
end

function socket_client:connect(timeout)
    if not self._modem then return end

    self:write("request_connect")
    local timer_id = 0
    if timeout then timer_id = os.startTimer(timeout) end

    while true do
        local ev, p1, p2, p3, p4 = os.pullEvent()

        if timeout and ev == "timer" and p1 == timer_id then
            return false
        elseif ev == "modem_message" then
            if p4:find("success") ~= nil then
                return true
            end
        end
    end

    self._modem.closeAll()

    return false
end

function socket_client:listen()
    if not self._modem then return end

    self._modem.open(self._channel)
    self._modem.open(self._reply_channel)

    while true do
        local ev, p1, p2, p3, p4 = os.pullEvent("modem_message")
        if p2 == self._reply_channel then
            return p4
        end
    end

    self._modem.closeAll()

    return ""
end

function socket_client:read()
    return self:listen()
end

function socket_client:write(msg)
    if not self._modem then return end

    self._modem.open(self._channel)
    self._modem.transmit(self._channel, self._reply_channel, msg)
    self._modem.closeAll()
end
setmetatable(socket_client, socket_client)

local text_utils = {}
text_utils.last = function(str, tok)
    local pos = -1

    while str:find(tok, pos + 1) ~= nil do
        pos = str:find(tok, pos + 1)
    end

    return (pos < 0 and 0 or pos - 1)
end

function string:split(sep)
        local sep, fields = sep or ":", {}
        local pattern = string.format("([^%s]+)", sep)
        self:gsub(pattern, function(c) fields[#fields+1] = c end)
        return fields
end

local arg = {...}

if arg[1] ~= nil and arg[1]:lower() == "help" then
    print("Usage:\nFTP_client [server channel] [client channel]")
    return
end

local ch = arg[1] == nil and 12 or (tonumber(arg[1]) == nil and 12 or tonumber(arg[1]))
local reply_ch = arg[2] == nil and 13 or (tonumber(arg[2]) == nil and 13 or tonumber(arg[2]))
local socket = socket_client(ch, reply_ch)

if type(socket) == "number" and socket == -1 then
    print("No modem found.")
    return
end

local remote_dir = "/"
local local_dir = shell.getRunningProgram():sub(0, text_utils.last(shell.getRunningProgram(), "/"))
local history = {}

local function cmd_cd(c, str)
    socket:write("cmd:" .. str)
    local d = socket:read(1)
    if d == -1 then
        print("Error reading from server")
    else
        remote_dir = d
    end

    return socket:read(1)
end

local function cmd_ls(c, str)
    socket:write("cmd:" .. str)
    local l = socket:read(1)
    if l == -1 then
        print("Error reading from server.")
    else
        if l ~= "" then
            print(l)
        end
    end
end

local function cmd_lls(c, str)
    local p = c[2]
    if not fs.exists(local_dir .. (p and "/" .. p or "")) then
        return "no_such_file"
    end

    local l = fs.list(local_dir .. (p and "/" .. p or ""))
    local s = ""
    for k, v in ipairs(l) do
        s = s .. v .. "\n"
    end
    s = s:sub(1, #s - 1)
    print(s)
end

local function cmd_mkdir(c, str)
    socket:write("cmd:" .. str)
    local l = socket:read(1)
    if l == -1 then
        print("Error reading from server.")
    else
        return l
    end
end

local function cmd_lcd(c, str)
    local p = c[2]
    if p == ".." then
        local_dir = local_dir:sub(1, text_utils.last(local_dir, "/"))
    elseif p ~= "." then
        if fs.isDir(local_dir .. "/" .. p) then
            local_dir = local_dir .. "/" .. p
        else
            return "no_such_file"
        end
    end

    return local_dir .. "/"
end

local function cmd_delete(c, str)
    socket:write("cmd:" .. str)
    local l = socket:read(1)
    if l == -1 then
        print("Error reading from server.")
    else
        return l
    end
end

local function cmd_rmdir(c, str)
    socket:write("cmd:" .. str)
    local l = socket:read(1)
    if l == -1 then
        print("Error reading from server.")
    else
        return l
    end
end

local function cmd_put(c, str)
    local t = os.time()
    if not c[2] then
        return "wrong_args"
    end

    if fs.isDir(local_dir .. "/" .. c[2]) then
        return "custom_err Cannot upload directory. Use 'rput' or 'mput' instead."
    end

    if not fs.exists(local_dir .. "/" .. c[2]) then
        return "no_such_file"
    end

    socket:write("cmd:" .. str)
    local l = socket:read(1)
    if l == -1 then
        print("Error reading from server.")
        return "unknown_error"
    elseif l == "ready" then
        local f = io.open(local_dir .. "/" .. c[2], "r")
        local data = f:read("*a")
        f:close()

        socket:write(data)

        local res = socket:read(1)
        if res == -1 then
            return "unknown_error"
        else
            return (res == "" and "custom_err Wrote " .. #data .. " bytes in " .. (os.time() - t) * 0.0138 .. " seconds." or res)
        end
    else
        return l
    end
end

local function putfiles(dir, abs)
    local ret = cmd_mkdir({}, "mkdir " .. abs)
    if ret ~= "" then return ret end

    local l = fs.list(dir)

    for k, v in ipairs(l) do
        if fs.isDir(local_dir .. "/" .. dir .. "/" .. v) then
            putfiles(local_dir .. "/" .. dir .. "/" .. v, abs .. "/" .. v)
        else
            local ret = cmd_put({"put", local_dir .. "/" .. dir .. "/" .. v, abs .. "/" .. v}, "put asd " .. abs .. "/" .. v)
            if ret ~= "" then
                return ret
            end
        end
    end
end

local function cmd_rput(c, str)
    if not c[2] then
        return "wrong_args"
    end

    if not fs.exists(local_dir .. "/" .. c[2]) then
        return "no_such_file"
    end

    if not fs.isDir(local_dir .. "/" .. c[2]) then
        return "custom_err Given path is not a directory. Use 'put' instead."
    end

    ret = putfiles(local_dir .. "/" .. c[2], c[3] or c[2])
    return ret
end

local function cmd_get(c, str)
    if not c[2] then
        return "wrong_args"
    end

    if fs.isDir(local_dir .. "/" .. (c[3] or c[2])) then
        return "custom_err Cannot overwrite directory."
    end

    if fs.exists(local_dir .. "/" .. (c[3] or c[2])) then
        io.write("Overwrite file '" .. (c[3] or c[2]) .. "? (y/n) ")
        local ans = io.read()

        if ans:lower() ~= "y" and ans:lower() ~= "yes" then
            return ""
        end
    end

    socket:write("cmd:" .. str)

    local ret = socket:read()
    if ret == "ok" then
        socket:write("ready")
        local data = socket:read()

        local f = io.open(local_dir .. "/" .. (c[3] or c[2]), "w")
        f:write(data)
        f:close()

        ret = socket:read()
        return ret
    else
        return ret
    end
end

local function cmd_rget(c, str)
    if not c[2] then
        return "wrong_args"
    end

    if fs.isDir(local_dir .. "/" .. (c[3] or c[2])) then
        return "custom_err Cannot overwrite directory."
    end

    if fs.exists(local_dir .. "/" .. (c[3] or c[2])) then
        io.write("Overwrite file '" .. (c[3] or c[2]) .. "? (y/n) ")
        local ans = io.read()

        if ans:lower() ~= "y" and ans:lower() ~= "yes" then
            return ""
        end
    end

    socket:write("cmd:" .. str)

    local ret = socket:read()

    if ret == "ok" then
        socket:write("ready")
        local p = socket:read()
        while p ~= "__getfiles_done__" do
            if p:sub(1, 1) == "d" then
                fs.makeDir(local_dir .. "/" .. p:sub(2))
            else
                local data = socket:read()
                local f = io.open(local_dir .. "/" .. p:sub(2), "w")
                f:write(data)
                f:close()
            end

            p = socket:read()
        end

        ret = socket:read()

        return ret
    else
        return ret
    end
end

local help_text = {
    ["cd"] = "Usage:\ncd <dir>\n\nChanges directory to <dir> on remote\nmachine.";

    ["lcd"] = "Usage:\ncd <dir>\n\nChanges directory to <dir> on local\nmachine.";

    ["ls"] = "Usage:\nls [dir]\n\nLists files in current directory on remote\nmachine.\nIf [dir] is provided, files in that directory\nwill be listed instead.";

    ["lls"] = "Usage:\nls [dir]\n\nLists files in current directory on local\nmachine.\nIf [dir] is provided, files in that directory\nwill be listed instead.";

    ["quit"] = "Usage:\nquit|bye\n\nCloses the connection and exists the program.";

    ["pwd"] = "Usage:\npwd\n\nPrints the current directory on the remote\nmachine.";

    ["mkdir"] = "Usage:\nmkdir <dir>\n\nCreates the directory <dir> on the remote\nmachine.";

    ["delete"] = "Usage:\ndelete <file>\n\nDeletes the file <file> on the remote machine.\nCannot delete directories.";

    ["rmdir"] = "Usage:\nrmdir <dir>\n\nRemoves the directory <dir> on the remote\nmachine. Cannot delete files.";

    ["put"] = "Usage:\nput <local/path> [remote/path]\n\nUploads a file to the remote machine.\nIf [remote/path] is specified, it will upload\nto that filename, otherwise it will upload to\nas <local/path> on remote machine.\nCannot upload directories.";

    ["rput"] = "Usage:\nrput|mput <local/path> [remote/path]\n\nUploads a directory to the remote machine.\nIf [remote/path] is specified, it will upload\nto that filename, otherwise it will upload to\nas <local/path> on remote machine.\nCannot upload single files.";

    ["get"] = "Usage:\nget <remote/path> [local/path]\n\nDownloads a single file from <remote/path> on\nthe remote machine. If [local/path] is specified,\nit will save there, otherwise in <remote/path>.\nCannot download directories. Use 'rget' or 'mget'.";

    ["rget"] = "Usage:\nrget|mget <remote/path>\n\nDownloads the directory <remote/path> from the\nremote machine. The directory is saved as\n<remote/path>";
}
help_text["bye"] = help_text["quit"]
help_text["mput"] = help_text["rput"]
help_text["mget"] = help_text["rget"]

local function cmd_help(c, str)
    if c[2] ~= nil then
        local text = help_text[c[2] ]
        if text == nil then
            return "custom_err No help available for '" .. c[2] .. "'"
        end

        print(text .. "\n")

        return ""
    end

    print("Help for FTP:\ncd <dir>      - change directory on remote\nlcd <dir>     - change directory locally\nls [dir]      - list files on remote\nlls [dir]     - list files locally\nquit/bye      - close connection\npwd           - print current remote dir\nmkdir <dir>   - create directory on remote\ndelete <file> - remove file on remote\nrmdir <dir>   - remove directory on remote\nput <file> [remote_file] - upload file\nrput/mput <dir> [remote_dir] - upload dir\nget <remote_file> [file] - download file\nhelp          - show this screen\nhelp <cmd>    - help for specific command\n")
    return ""
end

local function main()
    print("Connecting...")
    if socket:connect(2) == false then
        return false
    end

    while true do
        io.write(local_dir .. "> ")
        local cmd = read(nil, history)
        table.insert(history, cmd)

        local w = string.split(cmd, " ")


        local ret = ""

        if w[1] ~= nil then
            if w[1]:lower() == "cd" then
                ret = cmd_cd(w, cmd)
            elseif w[1]:lower() == "ls" then
                ret = cmd_ls(w, cmd)
            elseif w[1]:lower() == "lls" then
                ret = cmd_lls(w, cmd)
            elseif w[1]:lower() == "lcd" then
                ret = cmd_lcd(w, cmd)
            elseif w[1]:lower() == "quit" or w[1]:lower() == "bye" then
                socket:write("request_disconnect")
                return true
            elseif w[1]:lower() == "pwd" then
                print(remote_dir)
            elseif w[1]:lower() == "mkdir" then
                ret = cmd_mkdir(w, cmd)
            elseif w[1]:lower() == "delete" then
                ret = cmd_delete(w, cmd)
            elseif w[1]:lower() == "rmdir" then
                ret = cmd_rmdir(w, cmd)
            elseif w[1]:lower() == "put" then
                ret = cmd_put(w, cmd)
            elseif w[1]:lower() == "mput" or w[1]:lower() == "rput" then
                ret = cmd_rput(w, cmd)
            elseif w[1]:lower() == "get" then
                ret = cmd_get(w, cmd)
            elseif w[1]:lower() == "rget" or w[1]:lower() == "mget" then
                ret = cmd_rget(w, cmd)
            elseif w[1]:lower() == "help" or w[1] == "?" then
                ret = cmd_help(w, cmd)
            else
                ret = "unknown_command"
            end
        end

        if ret == "unknown_error" then
            print("Unknown error.")
        elseif ret == "unknown_command" then
            print("Unknown command. Try 'help'")
        elseif ret == "wrong_args" then
            print("Insufficient arguments. Try 'help'")
        elseif ret == "no_such_file" then
            print("No such file or directory.")
        elseif ret == "invalid_path" then
            print("Invalid path.")
        elseif ret == "already_exists" then
            print("File or directory already exists.")
        elseif ret == "not_allowed" then
            print("Insufficient permissions.")
        elseif type(ret) == "string" and ret:sub(0, string.len("custom_err")) == "custom_err" then
            print(ret:sub(string.len("custom_err") + 2))
        end
    end

    return true
end

term.clear()
term.setCursorPos(1, 1)
print("Welcome to FTP!\nFor a list of commands, run 'help'")
if main() == true then
    term.clear()
    term.setCursorPos(1, 1)
    print("Thanks for using FTP!")
else
    print("Unable to connect.")
end
]]

local ftp_server = [[
local text_utils = {}
text_utils.last = function(str, tok)
    local pos = -1

    while str:find(tok, pos + 1) ~= nil do
        pos = str:find(tok, pos + 1)
    end

    return (pos < 0 and 0 or pos - 1)
end

function string:split(sep)
        local sep, fields = sep or ":", {}
        local pattern = string.format("([^%s]+)", sep)
        self:gsub(pattern, function(c) fields[#fields+1] = c end)
        return fields
end

-- Socket server class
local socket_server = {
    _modem         = false;
    _channel       = -1;
    _reply_channel = 0;
    _side          = "top";
    _connected     = false;
}
socket_server.__index = socket_server

socket_server.__call = function(self, rep_ch)
    local sides = {
        "right", "left",
        "top", "bottom",
        "front", "back"
    }

    local m = nil
    local side = "none"
    for k, v in ipairs(sides) do
        if peripheral.getType(v) == "modem" then
            side = v
            break
        end
    end

    if side == "none" then
        return -1
    end

    m = peripheral.wrap(side)

    local t = {
        _side          = s or "top";
        _reply_channel = rep_ch;
        _modem         = m;
    }
    setmetatable(t, socket_server)

    return t
end

function socket_server:accept(ch, timeout)
    if self._connected then return end
    if not self._modem then return end

    self._modem.open(ch)

    local timer_id = 0
    if timeout then timer_id = os.startTimer(timeout) end

    while true do
        local ev, p1, p2, p3, p4 = os.pullEvent()

        if timeout and ev == "timer" and p1 == timer_id then
            return false
        elseif ev == "modem_message" then
            if p4:find("request_connect") ~= nil then
                print("Client connected on channel " .. p2)
                self._channel = p2
                self._connected = true
                self._modem.transmit(self._channel, self._reply_channel, "success")
                return true
            end
        end
    end

    self._modem.closeAll()

    return false
end

function socket_server:accept_any(timeout)
    if self._connected then return end
    if not self._modem then return end

    for i = 0, 1000 do
        self._modem.open(i)
    end

    local timer_id = 0
    if timeout then timer_id = os.startTimer(timeout) end

    while true do
        local ev, p1, p2, p3, p4 = os.pullEvent()

        if timeout and ev == "timer" and p1 == timer_id then
            return false
        elseif ev == "modem_message" then
            if p4:find("request_connect") ~= nil then
                print("Client connected on channel " .. p3)
                self._channel = p3
                self._connected = true
                self._modem.transmit(self._channel, self._reply_channel, "success")
                return true
            end
        end
    end

    self._modem.closeAll()

    return false
end

function socket_server:listen()
    if not self._modem then return end

    while true do
        if self._channel ~= -1 then
            self._modem.open(self._channel)
            self._modem.open(self._reply_channel)

            local ev, p1, p2, p3, p4 = os.pullEvent("modem_message")
            if p2 == self._reply_channel then
                return p4
            end

            self._modem.closeAll()
        end
    end

    return ""
end

function socket_server:read()
    local r = self:listen()
    if r == "request_disconnect" then
        print("Client on channel ".. self._channel .. " disconnected.")
        self._connected = false
    end
    return r
end

function socket_server:write(msg)
    if not self._modem then return end

    self._modem.open(self._channel)
    self._modem.transmit(self._channel, self._reply_channel, msg)
    self._modem.closeAll()
end
setmetatable(socket_server, socket_server)

local arg = {...}

_print = function(...)
    if not bg then print(...) end
end

if arg[2] == nil and arg[1] ~= nil and (arg[1]:lower() == "-b" or arg[1]:lower() == "--background") then
    arg[3] = arg[1]
end

if arg[1] ~= nil and arg[1]:lower() == "help" then
    _print("Usage:\nFTP_server [channel] [options]\nIf the option -b is provided, the server will run in the background")
    return
end

local ch = arg[1] == nil and 12 or (tonumber(arg[1]) == nil and 12 or tonumber(arg[1]))

local server = socket_server(ch)

if type(server) == "number" and server == -1 then
    _print("No modem found.")
    return
end

local dir = ""
local bg = false

local function cd(p)
    if p == ".." then
        dir = dir:sub(1, text_utils.last(dir, "/"))
    elseif p ~= "." then
        if fs.isDir(dir .. "/" .. p) then
            dir = dir .. "/" .. p
        else
            server:write(dir .. "/")
            return "no_such_file"
        end
    end

    server:write(dir .. "/")
    return dir .. "/"
end

local function ls(p)
    if not fs.exists(dir .. (p and "/" .. p or "")) then
        server:write("")
        return "no_such_file"
    end

    local l = fs.list(dir .. (p and "/" .. p or ""))
    local s = ""
    for k, v in ipairs(l) do
        s = s .. v .. "\n"
    end
    s = s:sub(1, #s - 1)
    server:write(s)

    return ""
end

local function mkdir(p)
    if fs.exists(dir .. "/" .. p) then
        return "already_exists"
    end

    fs.makeDir(dir .. "/" .. p)

    return ""
end

local function delete(p)
    if not fs.exists(dir .. "/" .. p) then
        return "no_such_file"
    elseif fs.isReadOnly(dir .. "/" .. p) then
        return "not_allowed"
    elseif fs.isDir(dir .. "/" .. p) then
        return "custom_err Cannot remove a directory. Use 'rmdir' instead."
    end

    fs.delete(dir .. "/" .. p)

    return ""
end

local function rmdir(p)
    if not fs.exists(dir .. "/" .. p) then
        return "no_such_file"
    elseif fs.isReadOnly(dir .. "/" .. p) then
        return "not_allowed"
    elseif not fs.isDir(dir .. "/" .. p) then
        return "custom_err Cannot remove a file. Use 'delete' instead."
    end

    fs.delete(dir .. "/" .. p)

    return ""
end

local function put(p)
    if fs.isDir(dir .. "/" .. p) then
        return "custom_err Cannot overwrite directory."
    end

    server:write("ready")
    local data = server:read()
    local f = io.open(dir .. "/" .. p, "w")
    f:write(data)
    f:close()

    return ""
end

local function get(p)
    if not fs.exists(dir .. "/" .. p) then
        return "no_such_file"
    end

    if fs.isDir(dir .. "/" .. p) then
        return "custom_err Cannot download directory. Use 'rget' or 'mget' instead."
    end

    server:write("ok")
    local ret = server:read()
    if ret ~= "ready" then
        return "unknown_err"
    end

    local f = io.open(dir .. "/" .. p, "r")
    local data = f:read("*a")
    f:close()
    server:write(data)

    return ""
end

local function rget(p)
    if not fs.exists(dir .. "/" .. p) then
        return "no_such_file"
    end

    if not fs.isDir(dir .. "/" .. p) then
        return "custom_err Cannot download single files.\nUse 'get' instead."
    end

    server:write("ok")

    local function getfiles(path)
        server:write("d" .. path)
        local l = fs.list(dir .. "/" .. path)

        for k, v in ipairs(l) do
            if fs.isDir(dir .. "/" .. path .. "/" .. v) then
                getfiles(dir .. "/" .. path .. "/" .. v)
            else
                server:write("f" .. path .. "/" .. v)

                local ret = server:read()
                if ret ~= "ready" then
                    return ret
                end

                local f = io.open(dir .. "/" .. path .. "/" .. v, "r")
                local data = f:read("*a")
                f:close()

                server:write(data)
            end
        end
    end

    getfiles(p)
    server:write("__getfiles_done__")
end

local function main()
    server:accept_any()

    while true do
        if not server._connected then
            server:accept_any()
        end

        local msg = server:read()

        if msg:sub(1, 4) == "cmd:" then
            local cmd = msg:sub(5)
            _print("Command: " .. cmd)
            cmd = string.split(cmd, " ")

            if cmd[1]:lower() == "cd" then
                if not cmd[2] then
                    server:write("wrong_args")
                else
                    local ret = cd(cmd[2])
                    server:write(ret)
                end
            elseif cmd[1]:lower() == "ls" then
                local ret = ls(cmd[2] or "")
                server:write(ret)
            elseif cmd[1]:lower() == "mkdir" then
                if not cmd[2] then
                    server:write("wrong_args")
                else
                    local ret = mkdir(cmd[2])
                    server:write(ret)
                end
            elseif cmd[1]:lower() == "delete" then
                if not cmd[2] then
                    server:write("wrong_args")
                else
                    local ret = delete(cmd[2])
                    server:write(ret)
                end
            elseif cmd[1]:lower() == "rmdir" then
                if not cmd[2] then
                    server:write("wrong_args")
                else
                    local ret = rmdir(cmd[2])
                    server:write(ret)
                end
            elseif cmd[1]:lower() == "put" then
                if not cmd[2] then
                    server:write("wrong_args")
                else
                    local ret = put((cmd[3] ~= nil and cmd[3] or cmd[2]))
                    server:write(ret)
                end
            elseif cmd[1]:lower() == "get" then
                if not cmd[2] then
                    server:write("wrong_args")
                else
                    local ret = get(cmd[2])
                    server:write(ret)
                end
            elseif cmd[1]:lower() == "rget" or cmd[1]:lower() == "mget" then
                if not cmd[2] then
                    server:write("wrong_args")
                else
                    local ret = rget((cmd[3] ~= nil and cmd[3] or cmd[2]))
                    server:write(ret)
                end
            else
                server:write("unknown_command")
            end
        end
    end

    return ""
end

if arg[3] ~= nil and (arg[3]:lower() == "-b" or arg[3] == "--background") then
    bg = true
    term.clear()
    term.setCursorPos(1, 1)
    parallel.waitForAll(main, function() shell.run("shell") end)
else
    main()
end
]]

local arg = {...}

if not arg[1] then print("Usage:\ninstall server|client") else
    if arg[1]:lower() == "c" or arg[1]:lower() == "client" then
        local f = io.open("ftp_client", "w")
        f:write(ftp_client)
        f:close()
        print("Installed to 'ftp_client'.\nRun 'ftp_client help' for information about using it.")
    elseif arg[1]:lower() == "s" or arg[1]:lower() == "server" then
        local f = io.open("ftp_server", "w")
        f:write(ftp_server)
        f:close()
        print("Installed to 'ftp_server'.\nRun 'ftp_server' help' for information about using it.")
    end
end