CloudChat Server V2

local modem = peripheral.find("modem")
local event, side, sChannel, id, data, dist
local sessions = {}
local channel = math.random(50000, 60000)
local topBar = window.create(term.native(), 1, 1, 52, 1)
local bg = window.create(term.native(), 1, 2, 52, 15)
local chatBox = window.create(term.native(), 1, 17, 51, 3)

chatBox.setBackgroundColor(colors.gray)
chatBox.clear()
bg.setBackgroundColor(colors.lightGray)
bg.clear()
bg.setCursorPos(1, 2)
topBar.setBackgroundColor(colors.blue)
topBar.clear()
topBar.setCursorPos(1, 1)
topBar.write("Cloud Chat                                   Server")

modem.open(os.getComputerID())


local function writeMsg(input)
  input = input .. " "
  local recursive
  if #input > 50 and input:find("%s") then
    recursive = true
    local space = input:find("%s", 50)
    local line = input:sub(0, space - 1)
    input = input:sub(space + 1)
    bg.write(line)
  else
    recursive = false
    bg.write(input)
  end

    local x, y = bg.getCursorPos()
    if y >= 15 then
    bg.scroll(1)
    bg.setCursorPos(1, y)
  else
    bg.setCursorPos(1, y + 1)
  end
  if recursive then
    writeMsg(input)
  end
end

local function receive()
    event, side, sChannel, id, data, dist = os.pullEvent("modem_message")
end

local function send(id, msg)
    modem.transmit(id, os.getComputerID(), msg)
end

local function indexOf(table, val)
  for index, tmp in pairs(table) do
    if tmp == val then
      return index
    end
  end
  return nil
end

local function getSID()
  local rand = math.random(0, 10000)
  for index, tmp in pairs(sessions) do
    if tmp == rand then
      return getSID()
    end
  end
  return rand
end

local function input()
    chatBox.clear()
    chatBox.setCursorPos(1, 1)
    term.redirect(chatBox)
    data = read()
end

while true do
    event = parallel.waitForAny(receive, input)
    if event == 1 then
        local sid, user, msg
        if data:find(":") then
            local c = data:find(":")
            sid = tonumber(data:sub(0, c - 1))
            msg = data:sub(c + 1)
            user = indexOf(sessions, sid)
            if user == nil then
                send(id, "No such session")
            elseif msg:sub(0, 1) == "!" then
                if msg == "!logout" then
                    sessions[user] = nil
                    send(id, "You have been logged out")
                elseif msg:find("%s") then
                    local space = msg:find("%s")
                    local command = msg:sub(0, space - 1)
                    if command == "!nick" then
                        local newName = msg:sub(space + 1)
                        sessions[newName] = sid
                        sessions[user] = nil
                        msg = (user .. " changed nick to " .. newName)
                        send(channel, msg)
                        writeMsg(msg)
                    end
                elseif msg == "!list" then
                    msg = "Users: "
                    for index, data in pairs(sessions) do
                        msg = msg .. " " .. index
                    end
                    send(id, msg)
                elseif msg == "!whoami" then
                    send(id, user)
                else
                    send(id, "No such command")
                end
            else
                msg = (user .. "> " .. msg)
                send(channel, msg)
                writeMsg(msg)
            end
        else
            user = data
            if sessions[user] == nil then
                sessions[user] = getSID()
                modem.transmit(id, channel, sessions[user])
            else
                send(id, "Username in use")
            end
        end
    else
        if data ~= "" then
            send(channel, "Server> " .. data)
            writeMsg("Server> " .. data)
        end
    end
end