Heimbriech Tablet OS - Credit Application

local oldPull = os.pullEvent
os.pullEvent = os.pullEventRaw
--this program acts as a Credit Card, to make things less messy
Requested_Amount = 0
Requester_ID = 0
Page = "Menu"
--the following Data is Only Called when needed, then its deleted for security reasons
AccountID = nil
AccountName = nil
AccountBalance = 0
Key = 0

start()
    term.setBackgroundColor("blue")
    term.setTextColor("white")
    Menu()
function start()

end

function Menu()
    term.clear()
    term.setCursorPos(1,1)
    print("---Credit-Remote-Transfer-V-1.0---")
    local event, key = os.pullEvent("key")
    if Page == "Menu" then
        print("Options")
        print("1 - Wait for Request")
        print("2 - Check Account")
        print("3 - Exit")
        while true do
            if key == keys.1 then
                Page == "Request"
                Menu()
            else if key == keys.2 then --Opens AccountPage
                Page == "Account"
                Menu()
            else if key == keys.3 then --Takes User to Main Program
                shell.run("")
            end
        end
    else if Page == "Request" then
        term.setCursorPos(1,2)
        print("CONNECTION HANDLER")
        term.setCursorPos(1,3)
        textutils.slowWrite("Waiting for Connection.....",6]
        sleep(10)
        Receive()
    else if Page == "Account" then
        Decrypter()
        term.setCursorPos(1,2)
        print("--ACCOUNT PAGE--")
        print("Account Name - "..AccountName)
        print("Account ID - "..AccountID)
        print("Account Balance - $"..AccountBalance)
        AccountName = nil
        AccountBalance = nil
        AccountID = nil
        while true do
            if key == keys.enter then
                Page = "Menu"
                Menu()
            end
        end
    end
end

function Receive()
    Decrypter()
    rednet.receive(AccountID,5)
    Requester_ID = id
    rednet.send(Requester_ID,"Amount")
    rednet.receive(AccountID,5)
    Requested_Amount = message
    if Requested_Amount < 0 then
        if Account_Balance+Requested_Amount >=0 then
            Payment()
        else
            rednet.send(Requester_ID,"Denied")
            sleep(4)
            print("Transaction Denied due to insignificant Funds")
            sleep(6)
            Page = "Menu"
            Menu()
        end
    else
        Payment()
    end
end

function Payment()
    Decrypter()
    rednet.send(Requester_ID, "confirmed",Key)
    local h = fs.open(".SecuriedData","a")
    h.setCursorPos(1,4)
    local Decrypt = h.readline(5)
    h.writeline(h.readline(4)+(Requested_Amount*Decrpyt))
    h.close()
    Page = "Menu"
    print("Transfer Completed")
    AccountName = nil
    AccountBalance = nil
    AccountID = nil
    sleep(10)
    Menu()
end

function Decrypter()
    local h = fs.open(".BankDetails","r")
    AccountID = h.readline(2)
    AccountName = h.readline(3)
    local Encrypt_Balance = h.readline(4)
    local DecryptKey_Balance = h.readline(5)
    AccountBalance = Encrypt_Balance/DecryptKey_Balance
    h.close()
end
os.pullEvent = oldPull