tv

function lsh(value,shift)
    return (value*(2^shift)) % 256
end
function rsh(value,shift)
    return math.floor(value/2^shift) % 256
end
function bit(x,b)
    return (x % 2^b - x % 2^(b-1) > 0)
end
function lor(x,y)
    result = 0
    for p=1,8 do result = result + (((bit(x,p) or bit(y,p)) == true) and 2^(p-1) or 0) end
    return result
end

-- Encoding
local base64chars = {[0]='A',[1]='B',[2]='C',[3]='D',[4]='E',[5]='F',[6]='G',[7]='H',[8]='I',[9]='J',[10]='K',[11]='L',[12]='M',[13]='N',[14]='O',[15]='P',[16]='Q',[17]='R',[18]='S',[19]='T',[20]='U',[21]='V',[22]='W',[23]='X',[24]='Y',[25]='Z',[26]='a',[27]='b',[28]='c',[29]='d',[30]='e',[31]='f',[32]='g',[33]='h',[34]='i',[35]='j',[36]='k',[37]='l',[38]='m',[39]='n',[40]='o',[41]='p',[42]='q',[43]='r',[44]='s',[45]='t',[46]='u',[47]='v',[48]='w',[49]='x',[50]='y',[51]='z',[52]='0',[53]='1',[54]='2',[55]='3',[56]='4',[57]='5',[58]='6',[59]='7',[60]='8',[61]='9',[62]='-',[63]='_'}
function encode(data)
    local bytes = {}
    local result = ""
    for spos=0,string.len(data)-1,3 do
        for byte=1,3 do bytes[byte] = string.byte(string.sub(data,(spos+byte))) or 0 end
        result = string.format('%s%s%s%s%s',result,base64chars[rsh(bytes[1],2)],base64chars[lor(lsh((bytes[1] % 4),4), rsh(bytes[2],4))] or "=",((#data-spos) > 1) and base64chars[lor(lsh(bytes[2] % 16,2), rsh(bytes[3],6))] or "=",((#data-spos) > 2) and base64chars[(bytes[3] % 64)] or "=")
    end
    return result
end

-- Decoding
local base64bytes = {['A']=0,['B']=1,['C']=2,['D']=3,['E']=4,['F']=5,['G']=6,['H']=7,['I']=8,['J']=9,['K']=10,['L']=11,['M']=12,['N']=13,['O']=14,['P']=15,['Q']=16,['R']=17,['S']=18,['T']=19,['U']=20,['V']=21,['W']=22,['X']=23,['Y']=24,['Z']=25,['a']=26,['b']=27,['c']=28,['d']=29,['e']=30,['f']=31,['g']=32,['h']=33,['i']=34,['j']=35,['k']=36,['l']=37,['m']=38,['n']=39,['o']=40,['p']=41,['q']=42,['r']=43,['s']=44,['t']=45,['u']=46,['v']=47,['w']=48,['x']=49,['y']=50,['z']=51,['0']=52,['1']=53,['2']=54,['3']=55,['4']=56,['5']=57,['6']=58,['7']=59,['8']=60,['9']=61,['-']=62,['_']=63,['=']=nil}
function decode(data)
    local chars = {}
    local result=""
    for dpos=0,string.len(data)-1,4 do
        for char=1,4 do chars[char] = base64bytes[(string.sub(data,(dpos+char),(dpos+char)) or "=")] end
        result = string.format('%s%s%s%s',result,string.char(lor(lsh(chars[1],2), rsh(chars[2],4))),(chars[3] ~= nil) and string.char(lor(lsh(chars[2],4), rsh(chars[3],2))) or "",(chars[4] ~= nil) and string.char(lor(lsh(chars[3],6) % 192, (chars[4]))) or "")
    end
    return result
end

done = 0
done2 = 0
print("TV v0.1 beta")

local args = {...}
if #args < 1 then
  print("Usage: tv <channel>")
  return
end



local channel = tonumber(args[1])
oldID = os.getComputerID()
function os.getComputerID()
  return channel
end
if not channel or channel > 65535 or channel < 0 then
  printError("Invalid channel")
  return
end

local modem = peripheral.find("modem")
modem.open(5555)
modem.transmit(5555,888,"request_subscrip_"..tostring(channel))
sleep(0.5)
repeat
  e = {os.pullEvent()}
  if e[1] == "modem_message" and e[3] == 5555 and e[5] == tostring(channel).."_FTA" then
    done = 1
  elseif e[1] == "modem_message" and e[3] == 5555 and e[5] == tostring(channel).."_PFP" then
    print("PFP Channel")
    if fs.exists("/disk") then
      print("Directory 'disk' found.")
      if disk.isPresent("bottom") then
        print("Disk found.")
        if fs.exists("/disk/.subscription_data") then
          print("Subscription number found.")
          f = fs.open("/disk/.subscription_data","r")
          a = f.readAll()
          f.close()
          f = nil
          print("Sending verification message...")
          modem.transmit(5555,tonumber(channel),"verify_sub_"..a)
          sleep(0.5)
          repeat
            e2 = {os.pullEvent()}
            if e2[1] == "modem_message" and e2[3] == 5555 and e2[5] == "verify_yes_"..tostring(channel) then
              done2 = 1
              print("Verified.")
            elseif e2[1] == "modem_message" and e2[3] == 5555 and e2[5] == "verify_no_"..tostring(channel) then
              term.clear()
              term.setCursorPos(1,1)
              print("You need an FRB Subscription for this channel!")
            end
          until done2 == 1
        end
      end
    end
  end
until done == 1

while true do
  local ev = {os.pullEventRaw()}
  if ev[1] == "terminate" then
    term.clear()
    term.setCursorPos(1, 1)
    print("Connection closed.")
    function os.getComputerID()
      return oldID
    end
    return
  elseif ev[1] == "modem_message" and ev[3] == channel and type(ev[5]) == "table" then
    msg = decode(ev[5])
    if term.current()[ msg[1] ] then
    pcall(term.current()[ msg[1] ], unpack(msg, 2))
    end
  end
end