NetBootClient

-- Better network boot, developed by PaymentOption --
VERSION = 1.0
-------------

-- Variables --
local tOS_List = {} -- Holds all of the available names of OS' to boot to.
-- ^^ FORMAT: tOS_List[n] = { Name, Version }
local NetworkID = 0 -- The network ID that we will retrieve OS' from and boot to an OS from.
local bConnected = false -- Whether or not we are connected to a network.

local bRunning = true -- Whether or not the program should be running.

local ScreenWidth, ScreenHeight = term.getSize() -- Holds the width and height of the screen.
local Selection = 1 -- The currently selected index in the OS' available.
---------------

-- Borrowed functions --
-- Following function taken from: http://lua-users.org/wiki/SplitJoin
-- Compatibility: Lua-5.1
function split(str, pat)
   local t = {}  -- NOTE: use {n = 0} in Lua-5.0
   local fpat = "(.-)" .. pat
   local last_end = 1
   local s, e, cap = str:find(fpat, 1)
   while s do
      if s ~= 1 or cap ~= "" then
     table.insert(t,cap)
      end
      last_end = e+1
      s, e, cap = str:find(fpat, last_end)
   end
   if last_end <= #str then
      cap = str:sub(last_end)
      table.insert(t, cap)
   end
   return t
end
------------------------

-- Drawing functions --
function cPrint( height, string ) -- Prints to the dead center of the screen.
    term.setCursorPos( ScreenWidth/2 - string.len( string )/2, height )
    term.write( string )
end

function rPrint( height, string ) -- Prints to the very right of the screen.
    term.setCursorPos( ScreenWidth - string.len( string ), height )
    term.write( string )
end

function Clear() -- Clears the screen.
    term.clear()
    term.setCursorPos( 1, 1 )
end

function DrawBorder()
    term.setCursorPos( 1, 1 )
    term.write( string.rep( "*", 50 ) )

    for i=2, 17 do
        term.setCursorPos( 1, i )
        term.write( "*" )
        term.setCursorPos( 50, i )
        term.write( "*" )
    end

    term.setCursorPos( 1, 18 )
    term.write( string.rep( "*", 50 ) )
end

function DrawLogo() -- Draws the PaymentOption signature logo.
    print( "     ____                                   __ " )
    print( "    / __ \\____ ___  ______ ___  ___  ____  / /_" )
    print( "   / /_/ / __ '/ / / / __ '__ \\/ _ \\/ __ \\/ __/" )
    print( "  / ____/ /_/ / /_/ / / / / / /  __/ / / / /_ " )
    print( " /_/    \\__,_/\\__, /_/ /_/ /_/\\___/_/ /_/\\__/ " )
    print( "             /____/                            " )
end

function limitRead( nLength, cReplaceChar )
      term.setCursorBlink( true )

      nLength = nLength or -1 -- -1 is unlimited
      sReturnString = ""

      xPos, yPos = term.getCursorPos()

      while true do
               event, char = os.pullEvent()

               if nLength ~= -1 and string.len( sReturnString ) >= nLength then term.setCursorBlink( false ); return sReturnString end -- Length check
                    if event == "char" then sReturnString = sReturnString .. char
                    elseif event == "key" then
                        if char == 28 then term.setCursorBlink( false ); return sReturnString -- Enter
                        elseif char == 14 then -- Backspace
                                term.setCursorPos( xPos, yPos )
                                term.write( string.rep( " ", string.len( sReturnString ) ) )
                                sReturnString = string.sub( sReturnString, 1, string.len( sReturnString )-1 )
                                term.setCursorPos( xPos, yPos )

                                if not cReplaceChar then term.write( sReturnString )
                                else term.write( string.rep( cReplaceChar, string.len( sReturnString ) ) ) end
                        end
                    end
                    term.setCursorPos( xPos, yPos )
                    term.write( string.rep( " ", string.len( sReturnString ) ) )
                    term.setCursorPos( xPos, yPos )
                    if not cReplaceChar then term.write( sReturnString )
                    else term.write( string.rep( cReplaceChar, string.len( sReturnString ) ) ) end
            end
    end
-----------------------

-- Screen drawing functions --
function DrawTitleScreen() -- Draws the opening screen to be displayed when the program is run.
    Clear()
    cPrint( 3, "Developed by" )
    term.setCursorPos( 1, 4 )
    DrawLogo()
    DrawBorder()
end

function DrawGetServerScreen() -- Draws the screen that prompts us to get a network ID to retrieve OS' from.
    Clear()
    cPrint( 2, "Enter a valid network ID" )
    DrawBorder()

    term.setCursorPos( ScreenWidth/2 - string.len( "Network ID: " ) + 4, 4 ) -- Set the cursor in the middle of the position offset enough to accept a 4 digit ID.
    term.write( "Networkd ID: " )
    NetworkID = tonumber( limitRead( 4 ) ) -- Get a network ID from the user and cast it to a number since read returns a string.

    if GetOS_List() then -- If we get the OS list successfully, then the connection was a success.
        bConnected = true -- We are connected.
    else -- If we do not get the OS list successfully, then the connection was a failure.
        bConnected = false -- We are not connected.
    end
end

function DrawBootOptionScreen()
    Clear()
    DrawBorder()
    cPrint( 2, "Available Operating Systems" )
    rPrint( 17, "Network Boot" )
    term.setCursorPos( 2, 17 )
    write( "Version: " .. VERSION )

    for i=1, #tOS_List do -- Draw out the list of available OS'.
        term.setCursorPos( 3, i + 3 ) -- Set the cursor to x = 3, y = i offset by 3 so it starts on line 4.

        if Selection == i then -- If the current OS is selected.
            term.write( "-> " .. tOS_List[i].Name ) -- Draw the OS' name with an arrow indicating that it is selected.
        else -- If the current OS is not selected.
            term.write( "   " .. tOS_List[i].Name ) -- Draw the OS' name without an arrow indicating that it is selected.
        end

        term.setCursorPos( 30, i + 3 ) -- Set the cursor at x = 30, y = i offset by 3 so it starts on line 4.
        term.write( "Ver: " .. tOS_List[i].Version ) -- Draw the OS' version regardless of it being selected.
    end
end
------------------------------

-- Key handling functions --
function HandleKeyPress( Key )
    if Key == 200 and Selection > 1 then -- If the key was to move the selection up on the screen.
        Selection = Selection - 1 -- Move the selection up.
    elseif Key == 208 and Selection < #tOS_List then -- If the key was to move the selection down on the screen.
        Selection = Selection + 1 -- Move the selection down.
    elseif Key == 28 then -- If the key was enter then get and execute the requested OS.
        local OS = RequestOS( Selection ) -- Attempt to get the OS in a function.

        if OS then -- If the OS was retrieved successfully.
            shell.run( "Temp_OS" ) -- Execute the OS.
            shell.exit()
        else -- If the OS was not retrieved successfully.
            -- Report the failure.
            cPrint( 17, "Networking failure." )
            sleep( 1.3 )
        end
    end
end
----------------------------

-- Networking functions --
function OpenExistantModem() -- Opens any modem found, returns true. Returns false if no modem was found.
    local tSides = rs.getSides()

    for i=1, #tSides do
        if peripheral.isPresent( tSides[i] ) and peripheral.getType( tSides[i] ) == "modem" then
            rednet.open( tSides[i] )
            return true
        end
    end

    return false
end

function Ping( ID ) -- Makes sure that we can contact the computer ID passed and that they are listening for requests.
    rednet.send( ID, "PingingYou" ) -- Send a request to the server.
    local sender, message = rednet.receive( 0.2 ) -- Wait for .2 seconds for a response.

    if sender == ID then -- If the message received was from the server we pinged.
        if message == "PingingYouBack" then -- If the message received was a ping acknowledgement.
            return true -- Report a successfull ping.
        else -- If the message received was not a ping acknowledgement.
            return false -- Report an unsuccessfull ping.
        end
    else -- If the message received was not from the server we pinged.
        return false -- Report an unsuccessfull ping.
    end
end

function GetOS_List() -- Gets the available list of OS' from the network computer.
    if Ping( NetworkID ) then -- If we can contact the network computer.
        rednet.send( NetworkID, "AllPlease" ) -- Request the OS'.
        local sender, message = rednet.receive( 0.2 ) -- Wait for a response from the network for .2 seconds.

        if sender == NetworkID then -- If the message received was from the network computer.
            local DownloadedList = split( message, "@#DS!" ) -- Split the message into a table by pattern !SP!.

            for i=1, #DownloadedList, 2 do -- Iterate through every other index of the downloaded list table.
                tOS_List[#tOS_List+1] = { Name = DownloadedList[i], Version = tonumber( DownloadedList[i+1] ) }
                -- ^^ Fill the OS_List table with the appropriate values.
            end

            return true -- Report a successfull download.
        else -- If the message was not from the network.
            return false -- Report a failure.
        end
    else -- If we cannot contact the network compute.r
        return false -- Report a failure.
    end
end

function RequestOS( OS_Index ) -- Requests the OS passed from the network and loads it into a usable function. Returns the function or false.
    if Ping( NetworkID ) then -- If we can contact the network.
        rednet.send( NetworkID, "OS_Number_" .. OS_Index ) -- Request the OS by Index in the OS table.
        local sender, message = rednet.receive( 0.2 ) -- Wait for a response from the network computer for .2 seconds.

        if sender == NetworkID then -- If the message received was from the network computer.
            if message then -- If the message is not equal to nil.
                if fs.exists( "Temp_OS" ) then
                    fs.delete( "Temp_OS" )
                end

                local File = fs.open( "Temp_OS", "w" )
                File.write( message )
                File.close()

                return true
            else -- If the message is equal to nil.
                return false -- Report a failure.
            end
        else -- If the message received was not from the network computer.
            return false -- Report a failure.
        end
    else -- If we cannot contact the network.
        return false -- Report a failure.
    end
end
--------------------------

-- Main loop function --
function MainLoop()
    if bConnected then -- If the connection was a success.
        DrawBootOptionScreen() -- Draw the available OS' to boot from.

        local event, key = os.pullEvent( "key" ) -- Wait for a key press.
        HandleKeyPress( key ) -- Handle the key press that occured.
    else -- If the connection was a failure.
        bRunning = false -- Exit the program.
    end
end
------------------------

-- The program --
if not OpenExistantModem() then
    error( "No modem found." )
end

DrawTitleScreen() -- Draw the logo and credits.
sleep( 1.3 )

DrawGetServerScreen() -- Get the network ID to connect to.
cPrint( 14, "Connecting..." ) -- Inform the user that we are connecting.
sleep( 0.2 )

while bRunning do
    MainLoop()
end

if not bRunning then
    Clear()
    print( os.version() )
    print( "Connection failure: " .. shell.getRunningProgram() )
end
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