Messaging Application

local compName = os.getComputerID()
-- Defining the compName var thats default is the computer's ID

version = "1.1"
-- Defining the version for my updating program

rednet.open("back")
-- Opening the modem so computer can use rednet

local chatLog = {}
-- Defining the chatLog table

shell.run("clear")

function initMessage()

  shell.run("clear")
  term.setTextColor(colors.blue)
  print("Welcome to the messaging application!\n\nWhile using the application at any time you can see available commands by using /help.\n")
  -- Printing the first 2 messages in blue

  term.setTextColor(colors.lightBlue)
  print("Type in the channel you would like to connect to:")
  -- Printing the third message in light blue

  term.setTextColor(colors.white)
  prot = read()
  -- Defining the prot variable

  shell.run("clear")
  -- Clearing the screen the messaging can begin
end
-- The messages that appear once you run the application

function wordSplit(string)

   local out = {}

   for word in string:gmatch("%S+") do

      table.insert(out, word)
   end

   return out
end
-- Function for splitting a string into a table at the spaces

function toScreen(msg)

  table.insert(chatLog,#chatLog+1,msg)
  -- Inserting the latest message into the chatLog table

  local maxX,maxY = term.getSize()
  -- Defining the maximum dimensions for use in while loop

  while #chatLog > maxY-1 do

    table.remove(chatLog,1)
  end
  -- Removing the old chat messages

  local maxX,maxY = term.getSize()
  local curX,_ = term.getCursorPos()
  -- Getting the maximum size of the screen

  for y=1,maxY-1 do
    for x=1,maxX do

      term.setCursorPos(x,y)
      term.write(" ")
    end
  end
  -- Clearing the screen except for the last line (the chat box)

  term.setCursorPos(1,1)

  for i=1,#chatLog do

    print(chatLog[i])
  end
  -- Printing the chatLog

  term.setCursorPos(curX,maxY)
  -- Resetting the cursor's coordinates after print
end
-- Function that will log the messages to a file and will print the messages once done

function receive()
  while true do

    local id, msg = rednet.receive(prot)

    if msg[1] and msg[1] == "msgAPP" and msg[2] and tostring(msg[2]) then
      if msg[3] and tostring(msg[3]) then

        toScreen("<" .. msg[3] .. "> " .. msg[2])
        -- Receiving a message on the connected channel (protocol) and then displaying it using the toScreen() function
      else

        toScreen("<" .. id .. "> " .. msg[2])
        -- Defaulting the computer name to their ID
      end

      local _, height = term.getSize()
      term.setCursorPos(1,height)
      -- Resetting the cursor
    end
  end
end
-- Function that receives any rednet messages on the same protocol and will run in unison with the input() function

function input()
  while true do

    local _, height = term.getSize()
    term.setCursorPos(1,height)
    local inp = read()
    -- First moving the cursor to the bottom left of the screen and then getting a input from the user

    if inp:sub(1,1) == "/" then
      -- Seeing if the user has entered a command or not

      local inpTab = wordSplit(inp)
      -- Splitting the command into a table

      if inpTab[1]:lower() == "/help" then

        toScreen("<console> /exit - will exit the messaging application\n/nick - change your nickname")
        -- First checking if the command is help and then displaying the help message if it is

      elseif inpTab[1]:lower() == "/exit" then

        rednet.broadcast({"msgAPP","Has disconnected.",compName})
        break
        -- First checking if the command is exit and then breaking the initial while loop so that the entire program will stop.

      elseif inpTab[1]:lower() == "/nick" then
        if inpTab[2] and #inpTab[2] <= 15 then

          compName = inpTab[2]
          toScreen("<console> I have changed my name to " .. inpTab[2])
          rednet.broadcast({"msgAPP","Is the new name of " .. os.getComputerID(),compName},prot)
          -- Broadcasting when you update your nickname

        elseif inpTab[2] and #inpTab[2] >= 16 then

          toScreen("<console> Nick too long. Has to be 15 characters or less.")
          -- If the nick is too long then it will be caught here
        else

          toScreen("<console> Usage: /nick *new nickname*")
          -- Printing the usage of the nick command
        end
      else

        toScreen('<console> Unknown command. Type "/help" for options.')
        -- Catching any other commands that aren't recognised and displaying an error message
      end
    elseif inp ~= "" then

      toScreen("<me> " .. inp)
      rednet.broadcast({"msgAPP",inp,compName},prot)
      -- If the input isn't a command it will get broadcasted across the same channel (protocol) to other connected computers
    else

      toScreen()
    end
  end
end
-- Function that will get the user input and detect if its a command or not

initMessage()
-- Running the initMessage() function so the channel gets defined

if prot ~= "" then

  toScreen("Connected to: " .. prot)
else

  toScreen("Connected to the global channel.")
end
-- Seeing if the channel has been entered or not and giving the appropriate message

parallel.waitForAny(input,receive)
-- Running both input() and receive() at the same time