OC-TELNET : An Telnet Client For OpenComputers

local component = require("component")
local event = require("event")
local term = require("term")
local internet = component.internet
local computer = require("computer")
local keyboard = require("keyboard")
local gpu = component.gpu

local IAC = string.char(255)
local DONT = string.char(254)
local DO = string.char(253)
local WONT = string.char(252)
local WILL = string.char(251)
local SB = string.char(250)
local SE = string.char(240)
local GA = string.char(249)
local EL = string.char(248)
local EC = string.char(247)
local AYT = string.char(246)
local AO = string.char(245)
local IP = string.char(244)
local BREAK = string.char(243)
local DM = string.char(242)
local NOP = string.char(241)

local ECHO = string.char(1)
local SUPPRESS_GO_AHEAD = string.char(3)
local TERMINAL_TYPE = string.char(24)
local NAWS = string.char(31)

local localEcho = true

local function handleTelnetCommand(connection, cmd)
    if cmd:sub(1, 1) == IAC then
        if cmd:len() == 2 then
            local command = cmd:sub(2, 2)
            if command == GA then
            elseif command == EL then
                io.write("\27[2K")
            elseif command == EC then
                io.write("\b \b")
            elseif command == AYT then
                connection.write("\r\nYes, I'm here\r\n")
            elseif command == AO then
                io.write("\r\nOutput aborted\r\n")
            elseif command == IP then
                io.write("\r\nProcess interrupted\r\n")
            elseif command == BREAK then
                io.write("\r\nBreak received\r\n")
            elseif command == DM then
            elseif command == NOP then
            end
        elseif cmd:len() == 3 then
            local command = cmd:sub(2, 2)
            local option = cmd:sub(3, 3)
            if command == DO then
                if option == TERMINAL_TYPE then
                    connection.write(IAC .. WILL .. TERMINAL_TYPE)
                elseif option == NAWS then
                    local w, h = gpu.getResolution()
                    connection.write(IAC .. WILL .. NAWS)
                    connection.write(IAC .. SB .. NAWS .. string.char(math.floor(w / 256)) .. string.char(w % 256) .. string.char(math.floor(h / 256)) .. string.char(h % 256) .. IAC .. SE)
                else
                    connection.write(IAC .. WONT .. option)
                end
            elseif command == WILL then
                if option == ECHO then
                    localEcho = false
                    connection.write(IAC .. DO .. option)
                elseif option == SUPPRESS_GO_AHEAD then
                    connection.write(IAC .. DO .. option)
                else
                    connection.write(IAC .. DONT .. option)
                end
            elseif command == WONT then
                if option == ECHO then
                    localEcho = true
                end
            elseif command == SB then
                local subnegotiation = cmd:sub(4, -2)
                if option == TERMINAL_TYPE then
                    connection.write(IAC .. SB .. TERMINAL_TYPE .. "\0" .. "ANSI-BBS" .. IAC .. SE)
                elseif option == NAWS then
                    local w, h = gpu.getResolution()
                    connection.write(IAC .. SB .. NAWS .. string.char(math.floor(w / 256)) .. string.char(w % 256) .. string.char(math.floor(h / 256)) .. string.char(h % 256) .. IAC .. SE)
                end
            end
        end
        return true
    end
    return false
end

local function handleANSI(str)
    local i = 1
    while i <= #str do
        local c = str:sub(i, i)
        if c == "\27" then
            local seq, cmd = str:match("\27%[([%d;]*)([A-Za-z])", i)
            if seq and cmd then
                local params = {}
                for param in seq:gmatch("%d+") do
                    table.insert(params, tonumber(param))
                end

                if #params == 0 then
                    params = {1}
                end

                if cmd == "H" or cmd == "f" then
                    local x, y = params[2] or 1, params[1] or 1
                    term.setCursor(x, y)
                elseif cmd == "J" then
                    if params[1] == 2 then
                        term.clear()
                    elseif params[1] == 0 then
                        term.clearLine()
                    end
                elseif cmd == "K" then
                    term.clearLine()
                elseif cmd == "A" then
                    local x, y = term.getCursor()
                    term.setCursor(x, y - (params[1] or 1))
                elseif cmd == "B" then
                    local x, y = term.getCursor()
                    term.setCursor(x, y + (params[1] or 1))
                elseif cmd == "C" then
                    local x, y = term.getCursor()
                    term.setCursor(x + (params[1] or 1), y)
                elseif cmd == "D" then
                    local x, y = term.getCursor()
                    term.setCursor(x - (params[1] or 1), y)
                elseif cmd == "m" then
                    for _, param in ipairs(params) do
                        if param == 0 then
                            gpu.setForeground(0xFFFFFF)
                            gpu.setBackground(0x000000)
                        elseif param == 1 then
                        elseif param >= 30 and param <= 37 then
                            local colors = {
                                0x000000, 0xFF0000, 0x00FF00, 0xFFFF00,
                                0x0000FF, 0xFF00FF, 0x00FFFF, 0xFFFFFF
                            }
                            gpu.setForeground(colors[param - 29])
                        elseif param >= 40 and param <= 47 then
                            local colors = {
                                0x000000, 0xFF0000, 0x00FF00, 0xFFFF00,
                                0x0000FF, 0xFF00FF, 0x00FFFF, 0xFFFFFF
                            }
                            gpu.setBackground(colors[param - 39])
                        end
                    end
                end
                i = i + #seq + 3
            else
                io.write(c)
                i = i + 1
            end
        else
            io.write(c)
            i = i + 1
        end
    end
end

local function connectTelnet(host, port)
    local connection = internet.connect(host, port)
    if not connection then
        print("Failed to connect to " .. host .. ":" .. port)
        return
    end

    print("Connecting to " .. host .. ":" .. port)
    local timeout = 10
    local start = computer.uptime()
    while not connection.finishConnect() do
        if computer.uptime() - start > timeout then
            print("Connection timed out")
            connection.close()
            return
        end
        os.sleep(0.1)
    end

    term.clear()
    print("Connected!")

    local buffer = ""
    while true do
        local data = connection.read(1024)
        if data then
            buffer = buffer .. data
            while true do
                local cmdStart, cmdEnd = buffer:find(IAC .. ".?.?")
                if cmdStart then
                    local cmd = buffer:sub(cmdStart, cmdEnd)
                    if handleTelnetCommand(connection, cmd) then
                        buffer = buffer:sub(1, cmdStart - 1) .. buffer:sub(cmdEnd + 1)
                    else
                        break
                    end
                else
                    break
                end
            end

            if #buffer > 0 then
                handleANSI(buffer)
                io.flush()
                buffer = ""
            end
        end

        local e = {event.pull(0.05)}
        if e[1] == "key_down" then
            local char, code = e[3], e[4]
            if keyboard.isControlDown() and keyboard.isAltDown() and char == 46 then
                print("\nDisconnecting...")
                break
            elseif keyboard.isControlDown() then
                if char >= 1 and char <= 26 then
                    connection.write(string.char(char))
                    if localEcho then
                        io.write("^" .. string.char(char + 64))
                    end
                end
            elseif code == 28 then
                connection.write("\r\n")
                if localEcho then
                    io.write("\r\n")
                end
            elseif code == 14 then
                connection.write("\b")
                if localEcho then
                    local x, y = term.getCursor()
                    if x > 1 then
                        term.setCursor(x - 1, y)
                        term.write(" ")
                        term.setCursor(x - 1, y)
                    end
                end
            else
                connection.write(string.char(char))
                if localEcho then
                    io.write(string.char(char))
                end
            end
            io.flush()
        end
    end

    connection.close()
    print("Disconnected. Press any key to exit.")
    event.pull("key_down")
end

local function displayLogo()
    local maxResolution = {gpu.getResolution()}
    local tier = (maxResolution[1] >= 160 and maxResolution[2] >= 50) and 3 or (maxResolution[1] >= 80 and maxResolution[2] >= 25) and 2 or 1
    term.clear()

    if tier == 1 then
        print([[
            ░█▀█░█▀▀░░░░░▀█▀░█▀▀░█░░░█▀█░█▀▀░▀█▀
            ░█░█░█░░░▄▄▄░░█░░█▀▀░█░░░█░█░█▀▀░░█░
            ░▀▀▀░▀▀▀░░░░░░▀░░▀▀▀░▀▀▀░▀░▀░▀▀▀░░▀░
        ]])
    else
        print([[
________________   ___________________________   __________________
__  __ \_  ____/   ___  __/__  ____/__  /___  | / /__  ____/__  __/
_  / / /  / _________  /  __  __/  __  / __   |/ /__  __/  __  /
/ /_/ // /___/_____/  /   _  /___  _  /___  /|  / _  /___  _  /
\____/ \____/      /_/    /_____/  /_____/_/ |_/  /_____/  /_/
        ]])
    end

    print("OC-TELNET Client made by nonogamer9")
end

while true do
    displayLogo()
    print("Enter the host and port to connect (e.g., example.com 23):")
    print("Or type 'exit' to quit the program.")
    local input = io.read()
    if input:lower() == "exit" then
        break
    end

    local host, port = input:match("(%S+)%s+(%d+)")
    if host and port then
        connectTelnet(host, tonumber(port))
    else
        print("Invalid input. Please provide a host and port.")
        os.sleep(2)
    end
end

print("Thank you for using OC-TELNET. Goodbye!")