function main()
    while true do
        ::Start::
        -- Check for inserted floppy.
        term.setCursorPos(1,1)
        term.clear()
        monitor.clear()
        print("Bitte Bankkarte in Laufwerk stecken.")
        term.setCursorPos(1,3)
        print("Für eine neue karte:")
        term.setCursorPos(3,4)
        print("1. Karte aus box holen.")
        term.setCursorPos(3,5)
        print("2. Karte in Laufwerk schieben.")
        local event, side = os.pullEvent("disk")
        if ~login() then
            term.setCursorPos(1,1)
            term.clear()
            monitor.clear()
            print("Bankkarte ungültig!")
            drive.eject("front")
            sleep(3)
            goto Start
        end

        -- Let user choose between (überweisen, karte erstellen).
        term.setCursorPos(1,1)
        term.clear()
        monitor.clear()
        term.setBackgroundColor(4096)
        term.setCursorPos(1,1)
        print("Überweisen")
        term.setCursorPos(1,2)
        print("Placeholder")
        term.setBackgroundColor(32768)
        while true do
            local event, side, x, y = os.pullEvent()
            if event == "monitor_touch" then
                if y == 1 then
                elseif y == 2 then
                    break
                elseif y == 3 then
                    break
                end
            end
        end
        drive.eject("front")
    end
end

function login()
    local name = ""
    local id = ""
    local password = ""

    -- Check who's disk it is.
    name = drive.getLabel(drive_pos)

    -- Get unique id from disk.
    id = drive.getID(drive_pos)

    -- Read bank card and decrypt password.
    if ~fs.exists(card_name) then
        return false
    end
    local file = fs.open(card_name, "r")
    password = encryption.Decrypt(file.readLine(), 5)

    -- get 4 digit pin, password and username from database.
    file = fs.open(database_path .. name .. ".txt")
    local client_name = file.readLine()
    local client_id = encryption.Decrypt(file.readLine(), 4)
    local client_pin = encryption.Decrypt(file.readLine(), 4)
    local client_password = encryption.Decrypt(file.readLine(), 4)

    -- compare password and username with database.
    if password ~= client_password or name ~= client_name then
        return false
    end
    
    -- Request 4 digit pin from user.
    for i = 1, 3 do
        local pin = ""
        local pin_char = ""
        term.clear()
        monitor.clear()
        term.setCursorPos(1,1)
        term.clearLine()
        print("Gib deine PIN ein: " .. pin_char)
        term.setBackgroundColor(4096)
        term.setCursorPos(1,2)
        print("789")
        term.setCursorPos(1,3)
        print("456")
        term.setCursorPos(1,4)
        print("123")
        term.setCursorPos(2,5)
        print("0")
        term.setBackgroundColor(32768)
        local event, side, x, y = os.pullEvent()
        for i = 1, 4 do
            if event == "monitor_touch" then
                if x == 2 and y == 5 then
                    pin = pin + "0"
                    pin_char = pin_char + "*"
                elseif x == 1 and y == 2 then
                    pin = pin + "7"
                    pin_char = pin_char + "*"
                elseif x == 2 and y == 2 then
                    pin = pin + "8"
                    pin_char = pin_char + "*"
                elseif x == 3 and y == 2 then
                    pin = pin + "9"
                    pin_char = pin_char + "*"

                elseif x == 1 and y == 3 then
                    pin = pin + "4"
                    pin_char = pin_char + "*"
                elseif x == 2 and y == 3 then
                    pin = pin + "5"
                    pin_char = pin_char + "*"
                elseif x == 3 and y == 3 then
                    pin = pin + "6"
                    pin_char = pin_char + "*"

                elseif x == 1 and y == 4 then
                    pin = pin + "1"
                    pin_char = pin_char + "*"
                elseif x == 2 and y == 4 then
                    pin = pin + "2"
                    pin_char = pin_char + "*"
                elseif x == 3 and y == 4 then
                    pin = pin + "3"
                    pin_char = pin_char + "*"
                end
            end
        end
        if pin == client_pin then
            term.clear()
            monitor.clear()
            print("Willkommen " .. name)
            sleep(3)
            return true
        end
    end
end

function send()
    -- Request amount and receiver.

    -- Send Money if available.
end

-- Card data structure:
    -- Password (Enc.5)
-- Database data structure:
    -- Username
    -- ID (Enc.4)
    -- PIN (Enc.4)
    -- Password (Enc.4)
    -- Cash

os.loadAPI("encryption.lua")
monitor = peripheral.wrap("top")
monitor.setTextScale(1)
drive = peripheral.wrap("bottom")
drive_pos = "right"
card_name = "disk/bank.txt"
database_path = "disk/users/"
database = peripheral.wrap("back")

main()