local sides = {"top", "bottom", "left", "right", "back", "front"}
local serverID = os.computerID()
local users = {}
local passwords = {}

function clear()
   term.clear()
   term.setCursorPos(1,1)
end

function updateAdminText()
      print("Welcome, admin.")
      print("What would you like to do?")
      print("[1] Make a new account.")
      print("[2] Quit the server.")
      print("[3] Return to normal server mode.")
      print("[4] Change the admin password.")
      print("[5] Print out the current users database.")
      write("> ")
end

function saveUsersVar()
   local usersFile = fs.open("users", "w")
   usersFile.write(textutils.serialize(users))
   usersFile.close()
end

function getUsersVar()
   local usersFile = fs.open("users", "r")
   users = textutils.unserialize(usersFile.readAll())
   usersFile.close()
end

function savePasswordsVar()
   local passwordsFile = fs.open("passwords", "w")
   passwordsFile.write(textutils.serialize(passwords))
   passwordsFile.close()
end

function getPasswordsVar()
   local passwordsFile = fs.open("passwords", "r")
   passwords = textutils.unserialize(passwordsFile.readAll())
   passwordsFile.close()
end

function bootUp()
   local rnetSuccess = false
   for i = 1, #sides do
      rednet.open(sides[i])
      if peripheral.getType(sides[i]) == "modem" then
         rnetSuccess = true
      end
   end
   if not rnetSuccess then
      print("Error: No wireless modem attached.")
      error()
   end
   if not fs.exists("adminPassword") then
      local adminPass = ""
      repeat
         clear()
         textutils.slowPrint("No admin password detected.")
         textutils.slowWrite("Enter a new password: ")
         adminPass = read()
      until adminPass ~= ""
      adminPassFile = fs.open("adminPassword", "w")
      adminPassFile.write(adminPass)
      adminPassFile.close()
   end
   if not fs.exists("users") then
      saveUsersVar()
   else
      getUsersVar()
   end
   if not fs.exists("passwords") then
      savePasswordsVar()
   else
      getPasswordsVar()
   end
end

function newAccount(newUsername, newPassword)
   local usernameKey = usernameToKey(newUsername)
   if usernameKey == nil then
      table.insert(users, 1, newUsername)
      table.insert(passwords, 1, newPassword)
      print("New account created:")
      print("New username: "..username)
      print("New password: "..password)
      sleep(2)
   else
      print("Username "..newUsername.." already in use:")
      print("Setting "..newUsername.."\'s password as "..newPassword..".")
      passwords[usernameKey] = newPassword
      sleep(3)
   end
   saveUsersVar()
   savePasswordsVar()
end

function usernameToKey(username)
   for i = 1, #users do
      if users[i] == username then
         return i
      end
   end
   return nil
end

function adminMode()
   while true do
      clear()
      updateAdminText()
      local option = read()
      if option == "1" then
         repeat
            write("Enter the new account's username: ")
            username = read()
            write("Enter the new account's password: ")
            password = read()
         until username ~= "" and password ~= ""
         newAccount(username, password)
      elseif option == "2" then
         clear()
         write("Entering normal command-line mode")
         os.sleep(0.2)
         textutils.slowPrint("...", 3)
         os.sleep(0.2)
         error()
      elseif option == "3" then
         clear()
         write("Returning to normal server mode")
         os.sleep(0.2)
         textutils.slowPrint("...", 3)
         os.sleep(0.2)
         return
      elseif option == "4" then
         local newPassword = ""
         repeat
            write("Enter the new password: ")
            newPassword = read()
         until newPassword ~= ""
         adminPassFile = fs.open("adminPassword", "w")
         adminPassFile.write(newPassword)
         adminPassFile.close()
         print("Successfully changed the password to "..newPassword..".")
         sleep(1.5)
      elseif option == "5" then
         clear()
         print("Username(Password)")
         for key, user in ipairs(users) do
            print(users[key].."("..passwords[key]..")")
            sleep(0.5)
         end
         print("Press any key to continue...")
         os.pullEvent("key")
         sleep(0.2)
      else
         print("Not a valid option.")
         os.sleep(1.5)
      end
   end
end

function updateText()
   print("This is the login server with ID "..serverID..".")
   print("Only the administrator can login here.")
   print("Enter the password to be granted access.")
   write("> ")
end

function normalMode()
   while true do
      clear()
      updateText()
      local password = read("*")
      local adminPassFile = fs.open("adminPassword", "r")
      adminPass = adminPassFile.readLine()
      adminPassFile.close()
      if password == adminPass then
         adminMode()
      else
         print("Password invalid!")
         sleep(2)
      end
   end
end

--======Rednet Message Interpreter™======--
----To Server----
--LOGIN = Signalling server to receive username and password in next 2 messages
----To Terminal----
--ERROR100 = Error recieving message
--ERROR101 = Username doesn't exist - ask admin to make one
--ERROR102 = Invalid password!
--VALIDATED = No errors! Yay!
--NOMOREFILES = No more files to send

function serverSub()
   while true do
      local senderID, message = rednet.receive()
      rednet.send(senderID, message)
      if message == "LOGIN" then
         local senderID2, username = rednet.receive(10)
         local senderID3, password = rednet.receive(10)
         if senderID ~= senderID2 or senderID ~= senderID3 then
            rednet.send(senderID, "ERROR100")
         else
            local accountKey = usernameToKey(username)
            if accountKey == nil then
               rednet.send(senderID, "ERROR101")
            else
               if password ~= passwords[accountKey] then
                  rednet.send(senderID, "ERROR102")
               else
                  rednet.send("VALIDATED")
                  if fs.exists("/"..username.."/") then
                     print(":D file sending :P")
                  end
                  rednet.send("NOMOREFILES")
               end
            end
         end
      end
   end
end

bootUp()
parallel.waitForAny(normalMode(), serverSub())