local term = require("term")
local component = require("component")
local event = require("event")
local m = component.modem
local str="0"
local userfile = "/home/.uname.txt"
local fs = require("filesystem")
local uname = fs.exists(userfile)

-- determine what channel people want to listen on
term.clear()
if uname then
  local handler = fs.open(userfile)
  user = handler:read(16)
  handler:close()
else
  term.write("You do not have a user profile. \n")
  term.write("Please enter a 16 character user name: ")
  local handler = fs.open(userfile, "w")
  handler:write(io.read())
  local handler = fs.open(userfile)
  user = handler:read(16)
  term.write("\n Username set to " .. user .. ". \n")
  handler:close()
end
term.write("What channel do you want to chat on: ")
local channel = io.read()
m.open(tonumber(channel))

-- begin event
function ModemFunction(_,_,from,port,_,message_)
event.listen("modem_message", ModemFunction)

-- decipher, and print
local cipher = "1234567890qwertyuiopasdfghjklzxcvbnm"
local function decrypt(str)
        str = str:gsub("%d",function(a) return string.char(cipher:find(a,nil,true)+47) end)
        str = str:gsub("%l",function(a) return string.char(cipher:find(a,nil,true)+86) end)
        return str
end
if string.sub(tostring(message), 1, 9)=="encrypted" then
str=tostring(message)
message=decrypt(str)
local strlngth=string.len(tostring(message))
message=string.sub(tostring(message), 10, strlngth)
print(tostring(message))

else
print(tostring(message))
end
end

-- send a message
term.write("is this going to be encrypted? (yes/no) \n")

-- register cipher
local cipher = "1234567890qwertyuiopasdfghjklzxcvbnm"

local function encrypt(str)
  str = str:gsub("%d",function(a) a=a:byte()-47 return cipher:sub(a,a) end)
  str = str:gsub("%l",function(a) a=a:byte()-86 return cipher:sub(a,a) end)
  return str
end

-- determine whether encryption should be used
local useEC=io.read()
if useEC=="yes" then
  term.clear()
  term.write("Encryption activated \n")
  sleep(5)
  term.clear()
end
while true do
  str= user .. ": " .. io.read()
  if tostring(str)== user .. ": " .. "endme" then
    term.clear()
    event.ignore("modem_message", ModemFunction)
    os.exit()
  end
  if useEC=="yes" then
    str= user .. ": " .. encrypt(str)
    str="encrypted" .. " " .. str
  end

-- send message
m.broadcast(tonumber(channel), str)
end