-- Constants for encryption and smart card
local ENCRYPTION_KEY = 42  -- Simple XOR key for encryption (can be stronger)

local SMART_CARD_FOLDER = "/disk/smartcards/"
local SMART_CARD_EXT = ".sc"

-- Encrypt a string using XOR encryption (simple method)
local function encryptPin(pin)
    local encrypted = {}
    for i = 1, #pin do
        encrypted[i] = string.char(string.byte(pin, i) ~ ENCRYPTION_KEY)
    end
    return table.concat(encrypted)
end

-- Decrypt the PIN stored on the smart card
local function decryptPin(encryptedPin)
    local decrypted = {}
    for i = 1, #encryptedPin do
        decrypted[i] = string.char(string.byte(encryptedPin, i) ~ ENCRYPTION_KEY)
    end
    return table.concat(decrypted)
end

-- Save smart card data (username, encrypted PIN) to a disk
local function saveSmartCard(username, encryptedPin)
    local smartCardFile = fs.combine(SMART_CARD_FOLDER, username .. SMART_CARD_EXT)

    if fs.exists(smartCardFile) then
        fs.delete(smartCardFile)  -- Overwrite existing smart card file
    end

    local file = fs.open(smartCardFile, "w")
    file.writeLine(encryptedPin)
    file.close()
end

-- Function to create a PIN and store it on the smart card
local function createSmartCard(username)
    drawPopupWindow("Create a Smart Card", {"Enter a PIN for your smart card (4 digits):"})

    term.setCursorPos(1, select(2, term.getSize()))
    term.write("Enter PIN: ")
    local pin = read("*")  -- Read PIN in masked format

    if #pin ~= PIN_LENGTH then
        drawPopupWindow("Error", {"PIN must be " .. PIN_LENGTH .. " digits."})
        os.sleep(2)
        return
    end

    -- Encrypt the PIN
    local encryptedPin = encryptPin(pin)

    -- Save to smart card
    saveSmartCard(username, encryptedPin)

    -- Success message
    drawPopupWindow("Smart Card Created", {"Your smart card has been created successfully!"})
    os.sleep(2)
end

-- Function to verify the smart card PIN during login
local function verifySmartCard(username)
    local smartCardFile = fs.combine(SMART_CARD_FOLDER, username .. SMART_CARD_EXT)

    if not fs.exists(smartCardFile) then
        return false  -- No smart card found
    end

    local file = fs.open(smartCardFile, "r")
    local encryptedPin = file.readLine()
    file.close()

    drawPopupWindow("Insert Smart Card", {"Please insert your smart card to continue..."})

    while true do
        local event, disk = os.pullEvent("disk")
        if event == "disk_insert" then
            if disk == SMART_CARD_FOLDER then
                -- Simulate smart card ID check (in reality, check disk ID here)
                local userInput = read("Enter PIN to authenticate: ")

                -- Decrypt and check PIN
                local decryptedPin = decryptPin(encryptedPin)
                if userInput == decryptedPin then
                    return true
                else
                    drawPopupWindow("Access Denied", {"Incorrect PIN!"})
                    os.sleep(2)
                    return false
                end
            end
        end
    end
end

-- Function to handle the setup and user creation for smart card authentication
local function setupSmartCard(username)
    -- Start by setting up the smart card for the user
    drawPopupWindow("Smart Card Setup", {"You are in setup mode. Please create a PIN for your smart card."})

    -- Call the function to create the smart card
    createSmartCard(username)

    -- Remove setup file once completed
    fs.delete(SCSETUP_FILE)
end

-- Function to authenticate using a smart card (during login)
local function insertSecurityCard(username)
    return verifySmartCard(username)
end

-- Main logic
local function main()
    term.setTextColor(colors.white)
    term.setBackgroundColor(colors.black)
    term.clear()

    local username

    -- Check if in setup mode
    if checkSetupMode() then
        -- Handle smart card setup during setup mode
        drawPopupWindow("Setup Mode", {"System is in setup mode. Please configure your smart card."})
        local username = selectUserFromList()
        setupSmartCard(username)  -- This will handle the smart card setup
        return
    end

    -- Check if AutoLogin is allowed
    local autoLoginUser = checkAutoLogin()
    if autoLoginUser then
        username = autoLoginUser
        drawPopupWindow("Autologin", {"Welcome back, " .. username .. "!"})
        os.sleep(2)
    else
        if fs.exists(SHOW_ALL_USERS_FILE) then
            username = selectUserFromList()
        else
            drawPopupWindow("Protected by Doggy OS Security", {"Enter username:"})
            username = read()
        end
    end

    -- Attempt smart card login first
    if insertSecurityCard(username) then
        drawPopupWindow("Access Granted", {"Security card verified. Welcome, " .. username .. "!"})
        os.sleep(2)
        saveCurrentUser(username)
        shell.run("/disk/os/gui")
        return
    end

    -- Fallback to password login if card verification fails or is bypassed
    if checkCredentials(username) then
        drawPopupWindow("Access Granted", {"Welcome, " .. username .. "!"})
        os.sleep(2)
        saveCurrentUser(username)
        shell.run("/disk/os/gui")
    else
        shell.run("/disk/os/lock.lua")
    end
end

main()