-- Function to generate a key for encryption and decryption
function generateKey()
    local chars = {}
    for i = 32, 126 do -- ASCII range for printable characters
        table.insert(chars, string.char(i))
    end

    local key = {}
    while #chars > 0 do
        local index = math.random(#chars)
        table.insert(key, table.remove(chars, index))
    end

    return table.concat(key)
end

-- Function to create a map from a key
function createMap(key)
    local map = {}
    for i = 32, 126 do
        map[string.char(i)] = key:sub(i - 31, i - 31)
    end
    return map
end

-- Function to invert a map
function invertMap(map)
    local invMap = {}
    for k, v in pairs(map) do
        invMap[v] = k
    end
    return invMap
end

-- Function to encrypt text using a key
function encrypt(text, key)
    local map = createMap(key)
    local encrypted = {}
    for i = 1, #text do
        local char = text:sub(i, i)
        table.insert(encrypted, map[char] or char)
    end
    return table.concat(encrypted)
end

-- Function to decrypt text using a key
function decrypt(text, key)
    local map = invertMap(createMap(key))
    local decrypted = {}
    for i = 1, #text do
        local char = text:sub(i, i)
        table.insert(decrypted, map[char] or char)
    end
    return table.concat(decrypted)
end

-- Function to save the key to a file
function saveKeyToFile(key, dir)
    local randomNumber = math.random(1, 1000)
    local fileName = dir .. "/key" .. randomNumber .. ".txt"
    local file = fs.open(fileName, "w")
    file.write(key)
    file.close()
    return fileName
end

-- Function to load the key from a file
function loadKeyFromFile(fileName)
    local file = fs.open(fileName, "r")
    local key = file.readAll()
    file.close()
    return key
end

-- Function to find the key file in a directory
function findKeyFile(dir)
    local files = fs.list(dir)
    for _, file in ipairs(files) do
        if file:match("^key%d+%.txt$") then
            return dir .. "/" .. file
        end
    end
    return nil
end

-- Function to create a new user
function createUser()
    term.clear()
    term.setCursorPos(1, 1)
    print("Enter new username:")
    local username = read()

    -- Check if the username already exists
    if fs.exists("/disk/users/" .. username) then
        print("Username already exists. Try again.")
        sleep(2)
        return
    end

    -- Create a directory for the new user
    fs.makeDir("/disk/users/" .. username)

    -- Prompt for password
    local password
    repeat
        term.clear()
        term.setCursorPos(1, 1)
        print("Enter password:")
        password = read("*")

        print("Confirm password:")
        local confirmPassword = read("*")

        if password ~= confirmPassword then
            print("Passwords do not match. Try again.")
            sleep(2)
        end
    until password == confirmPassword

    -- Encrypt the password before storing
    local key = generateKey()
    local encryptedPassword = encrypt(password, key)

    -- Store the encrypted password in a text file
    local file = fs.open("/disk/users/" .. username .. "/password.txt", "w")
    if file then
        file.write(encryptedPassword)
        file.close()
    else
        print("Failed to create password file.")
        sleep(2)
        return
    end

    -- Save the encryption key to a file
    saveKeyToFile(key, "/disk/users/" .. username)

    print("User created successfully.")
    sleep(2)
end

-- Function to delete a user
function deleteUser()
    term.clear()
    term.setCursorPos(1, 1)
    print("Enter username to delete:")
    local username = read()

    -- Check if the username exists
    if not fs.exists("/disk/users/" .. username) then
        print("User not found. Try again.")
        sleep(2)
        return
    end

    -- Check for the presence of block.txt
    if fs.exists("/disk/users/" .. username .. "/block.txt") then
        -- Display content of block.txt as an error message
        local file = fs.open("/disk/users/" .. username .. "/block.txt", "r")
        if file then
            local errorMessage = file.readAll()
            file.close()
            print(errorMessage)
        else
            print("Failed to read block file.")
        end
        sleep(2)
        return
    end

    -- Prompt for password to confirm deletion
    print("Enter password to confirm deletion:")
    local inputPassword = read("*")

    -- Read stored encryption key and password from files
    local key = loadKeyFromFile("/disk/users/" .. username)
    local file = fs.open("/disk/users/" .. username .. "/password.txt", "r")
    if file then
        local storedEncryptedPassword = file.readAll()
        file.close()

        -- Decrypt stored password and compare with input
        local storedPassword = decrypt(storedEncryptedPassword, key)
        if inputPassword == storedPassword then
            -- Delete the user directory
            fs.delete("/disk/users/" .. username)
            print("User deleted successfully.")
        else
            print("Incorrect password. Deletion failed.")
        end
    else
        print("Failed to read password file.")
    end

    sleep(2)
end

-- Function to view all users
function viewAllUsers()
    term.clear()
    term.setCursorPos(1, 1)
    print("All Users:")
    local users = fs.list("/disk/users")
    for _, user in ipairs(users) do
        if user ~= "root" then
            print(user)
        end
    end
    print("Press any key to continue...")
    read()
end

-- Function for password recovery by admin
function passwordRecovery()
    term.clear()
    term.setCursorPos(1, 1)
    print("Enter admin username:")
    local adminUsername = read()

    -- Check if the entered user has admin privileges
    if not fs.exists("/disk/users/" .. adminUsername .. "/admin.txt") then
        print("Permission denied. Admin access required.")
        sleep(2)
        return
    end

    -- Prompt for admin password
    print("Enter admin password:")
    local adminPassword = read("*")

    -- Read stored admin password from the file
    local adminFile = fs.open("/disk/users/" .. adminUsername .. "/password.txt", "r")
    local storedAdminPassword = adminFile.readAll()
    adminFile.close()

    -- Compare entered admin password with stored admin password
    if adminPassword == storedAdminPassword then
        print("Enter username for password reset:")
        local username = read()

        -- Check if the username exists
        if not fs.exists("/disk/users/" .. username) then
            print("User not found. Try again.")
            sleep(2)
            return
        end

        -- Confirm password reset
        print("Are you sure you want to reset the password for " .. username .. "? (y/n)")
        local confirm = read()
        if confirm:lower() ~= "y" then
            print("Password reset canceled.")
            sleep(2)
            return
        end

        -- Prompt for new password
        term.clear()
        term.setCursorPos(1, 1)
        print("Enter new password for " .. username .. ":")
        local newPassword = read("*")

        -- Store the new password in the text file
        local file = fs.open("/disk/users/" .. username .. "/password.txt", "w")
        file.write(newPassword)
        file.close()

        print("Password reset successfully.")
    else
        print("Incorrect admin password. Password reset failed.")
    end

    sleep(2)
end

-- Function to exit and run /disk/os/gui
function exitProgram()
    term.clear()
    term.setCursorPos(1, 1)
    print("Exiting program...")
    sleep(1)
    shell.run("/disk/os/gui")
    error("Exiting program.")
end

-- Function for Security Card Login (insert or enter ID)
function securityCardLogin(username)
    while true do
        term.clear()
        term.setCursorPos(1, 1)
        print("Security Card Manager")
        print("1. Add Card")
        print("2. Remove Cards")
        print("3. Show All Security Cards")
        print("4. Disable Security Card Login")
        print("5. Back to Main Menu")

        local choice = read()

        if choice == "1" then
            addCardMenu(username)
        elseif choice == "2" then
            removeCardsMenu(username)
        elseif choice == "3" then
            showAllSecurityCards(username)
        elseif choice == "4" then
            disableSecurityCardLogin(username)
        elseif choice == "5" then
            break
        else
            print("Invalid choice. Press any key to continue...")
            read()
        end
    end
end

-- Main menu loop
while true do
    term.clear()
    term.setCursorPos(1, 1)
    print("User Manager")
    print("1. Create User")
    print("2. Delete User")
    print("3. View All Users")
    print("4. Password Recovery")
    print("5. Exit and Run GUI")
    print("6. Security Card Login")
    print("7. Exit Program")

    local choice = read()

    if choice == "1" then
        createUser()
    elseif choice == "2" then
        deleteUser()
    elseif choice == "3" then
        viewAllUsers()
    elseif choice == "4" then
        passwordRecovery()
    elseif choice == "5" then
        exitProgram()
    elseif choice == "6" then
        -- Assuming username is known or passed as a parameter
        securityCardLogin("admin") -- Change "admin" to the actual admin username
    elseif choice == "7" then
        break
    else
        print("Invalid choice. Press any key to continue...")
        read()
    end
end