RedMail Server

function split(pString, pPattern)
   local Table = {}  -- NOTE: use {n = 0} in Lua-5.0
   local fpat = "(.-)" .. pPattern
   local last_end = 1
   local s, e, cap = pString:find(fpat, 1)
   while s do
          if s ~= 1 or cap ~= "" then
         table.insert(Table,cap)
          end
          last_end = e+1
          s, e, cap = pString:find(fpat, last_end)
   end
   if last_end <= #pString then
          cap = pString:sub(last_end)
          table.insert(Table, cap)
   end
   return Table
end

if not fs.exists("unread.mail") then
  local f = fs.open("unread.mail","w")
  f.close()
end

if not fs.exists("config.mail") then
  local f = fs.open("config.mail","w")
  print("Which side the modem is ? ")
  local s = read()
  f.write(s)
  f.close()
end

while true do
  local config = fs.open("config.mail","r")
  local modem_side = config.readLine()
  config.close()
  rednet.open(modem_side)
  id, message = rednet.receive()
  local splited = split(message,"|")
  local action = splited[1]
  if action == "send" then
    local receiver = splited[2]
    local sender = splited[3]
    local subject = splited[4]
    local corpse = splited[5]
    local f1 = fs.open("unread.mail","r")
    local data = f1.readAll()
    f1.close()
    local f = fs.open("unread.mail","w")
    f.write(data .. receiver .."|".. sender .."|".. subject .."|".. corpse .."§")
    f.close()
  elseif action == "fetch" then
    local user = splited[2]
    local f = fs.open("unread.mail","r")
    local fData = f.readAll()
    f.close()
    local newFData = ""
    local fetchedMails = ""
    local unreadNumber = 0
    for key,line in pairs(split(fData,"§")) do
       local sLine = split(line,"|")
       local receiver = sLine[1]
       if receiver == user then
         if fetchedMails == "" then
           fetchedMails = line .."§"
         else
           fetchedMails = fetchedMails .. line .. "§"
         end
       else
         unreadNumber = unreadNumber + 1
         if newFData == "" then
           newFData = line.."§"
         else
           newFData = newFData .. line .. "§"
         end
       end
    end
    local m = peripheral.wrap("front")
    m.clear()
    m.setCursorPos(1,1)
    m.setTextScale(1)
    m.write("Unread Mails : "..unreadNumber)
    if not fs.exists(user .."/archive.mail") then
      local archive = fs.open(user .."/archive.mail","w")
      archive.close()
    end
    local archiveData = fs.open(user .."/archive.mail","r")
    local archiveMails = archiveData.readAll()
    archiveData.close()
    local newArchive = fs.open(user .."/archive.mail","w")
    newArchive.write(archiveMails .. fetchedMails)
    newArchive.close()
    local newF = fs.open("unread.mail","w")
    newF.write(newFData)
    newF.close()
    rednet.send(id, fetchedMails)
  end
end