CatChat

-- DESCRIPTION: This program was made to be used as an alternative chat in servers that disabled the in-game chat.

local modem = peripheral.find("modem") or error("No modem attached", 0)
modem.open(43)

local name = nil
local messages = {}
local text = ""
local windowWidth, windowHeight = term.getSize()

function NameSelection()
    local error = false
    while (name == nil or #name < 1) do
        term.clear()

        term.setTextColor(colors.white)
        term.setCursorPos(1, 1)
        term.write("Welcome to CatChat! Please write your name.")

        if (error) then
            term.setTextColor(colors.red)
            term.setCursorPos(1, 6)
            term.write("The name is obligatory.")
        end

        term.setTextColor(colors.white)
        term.setCursorPos(1, 3)
        term.write("> ")
        term.setCursorPos(1, 3)
        name = read()

        error = true
    end
end

function PrintScreen()
    while (true) do
        term.setBackgroundColor(colors.white)
        term.clear()

        -- Received messages
        term.setTextColor(colors.red)
        local msgY = windowHeight-2
        for i=#messages, 1 do
            if (msgY <= 0) then
                break
            end

            local msg = messages[i]
            term.setCursorPos(1, msgY)
            term.write(msg)

            msgY = msgY -1
        end

        -- Current message
        paintutils.drawLine(1,windowHeight-1, 1,windowHeight-1, colors.black)
        term.setTextColor(colors.green)
        term.setCursorPos(1, windowHeight-1)
        term.write(text)

        sleep(0.5)
    end
end

function GetMessage()
    while (true) do
        local event, side, channel, replyChannel, message, distance = os.pullEvent("modem_message")
        table.insert(messages, message)
    end
end

function SendMessage(msg)
    if (msg == nil or msg == "") then
        return
    end

    modem.transmit(43, 43, "<" .. name .. "> " .. msg)
end

function WriteMessage()
    while true do
        local event, key, is_held = os.pullEvent("key")

        key = keys.getName(key)
        if (#key == 1) then
            text = text .. key
        elseif (key == "space") then
            text = text .. " "
        elseif (key == "backspace" and #key > 0) then
            text = string.sub(text, 1, #key-1)
        elseif (key == "enter") then
            SendMessage(text)
            text = text
        end
    end
end

-- Main
NameSelection()

parallel.waitForAny(
function()
    PrintScreen()
end,
function()
    GetMessage()
end,
function()
    WriteMessage()
end
)