-- 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)
    local fileName = "key.txt"  -- Fixed key file name
    local file = fs.open(fileName, "w")
    file.write(key)
    file.close()
    return fileName
end

-- Function to load the key from a file without deleting it
function loadKeyFromFile()
    local fileName = "key.txt"  -- Fixed key file name
    local path = fs.combine("/", fileName)
    if fs.exists(path) then
        local file = fs.open(path, "r")
        if file then
            local key = file.readAll()
            file.close()
            return key
        else
            print("Error: Unable to open key file.")
            return nil
        end
    else
        print("Error: Key file does not exist.")
        return nil
    end
end

-- Function to set or reset the password in the password file
-- and update the key file
function setPassword(newPassword)
    local key = generateKey()  -- Generate a new encryption key
    local encryptedPassword = encrypt(newPassword, key)

    local fileName = "pass.txt"  -- Fixed password file name
    local file = fs.open(fileName, "w")
    file.write(encryptedPassword)
    file.close()

    -- Save the key to key.txt
    saveKeyToFile(key)

    return true
end

-- Function to verify password during system startup
function verifyPassword(enteredPassword)
    local fileName = "pass.txt"  -- Fixed password file name
    local path = fs.combine("/", fileName)
    if fs.exists(path) then
        local file = fs.open(path, "r")
        if file then
            local encryptedPassword = file.readAll()
            file.close()

            local key = loadKeyFromFile()
            if key then
                local decryptedPassword = decrypt(encryptedPassword, key)
                return enteredPassword == decryptedPassword
            else
                print("Error: Unable to load encryption key.")
                return false
            end
        else
            print("Error: Unable to open password file.")
            return false
        end
    else
        print("Error: Password file does not exist.")
        return false
    end
end

-- Function to show protection screen options
function showProtectionScreen()
    term.clear()
    term.setCursorPos(1, 1)
    print("Doggy OS File System Protection")
    print()
    print("F1 - Unlock")
    print("F8 - Shutdown")
    print("F9 - Recover System")

    while true do
        local event, key = os.pullEvent("key")
        if key == keys.f1 then
            term.clear()
            term.setCursorPos(1, 1)
            print("Enter decryption password:")
            local password = read("*")

            if verifyPassword(password) then
                local key = loadKeyFromFile()
                if key then
                    processDirectory("/disk", decrypt, key)
                    shell.run("/disk/boot/BIOS")
                else
                    print("Error: Unable to load encryption key.")
                end
            else
                print("Incorrect password.")
            end

            return
        elseif key == keys.f8 then
            os.shutdown()
            return
        elseif key == keys.f9 then
            recoverSystem()
            return
        end
    end
end

-- Function to recover the system (delete disk and replace with recovery)
function recoverSystem()
    local files = fs.list("/disk")
    for _, file in ipairs(files) do
        local filePath = fs.combine("/disk", file)
        if not fs.isDir(filePath) then
            fs.delete(filePath)
        end
    end
    -- Optionally copy recovery files from a backup location or setup
    print("System recovered. Please restart your system.")
end

-- Function to encrypt files in a directory
function encryptDirectory(path, key)
    local files = fs.list(path)
    for _, file in ipairs(files) do
        local filePath = fs.combine(path, file)
        if fs.isDir(filePath) then
            encryptDirectory(filePath, key)
        else
            local file = fs.open(filePath, "r")
            local content = file.readAll()
            file.close()

            local encryptedContent = encrypt(content, key)

            file = fs.open(filePath, "w")
            file.write(encryptedContent)
            file.close()
        end
    end
end

-- Function to process files in a directory with a given process function
function processDirectory(path, processFunction, key)
    local files = fs.list(path)
    for _, file in ipairs(files) do
        local filePath = fs.combine(path, file)
        if fs.isDir(filePath) then
            processDirectory(filePath, processFunction, key)
        else
            local file = fs.open(filePath, "r")
            local content = file.readAll()
            file.close()

            local processedContent = processFunction(content, key)

            file = fs.open(filePath, "w")
            file.write(processedContent)
            file.close()
        end
    end
end

-- Function to encrypt the entire system ("/disk" directory)
function encryptSystem()
    local key = loadKeyFromFile()
    if key then
        encryptDirectory("/disk", key)
        print("System encrypted.")
    else
        print("Error: Unable to load encryption key.")
    end
end

-- Main Program
term.clear()
term.setCursorPos(1, 1)
print("Doggy OS File System Encryption")
print()
print("Initializing...")

local tArgs = {...}
local mode = tArgs[1]

if mode == "decrypt" then
    showProtectionScreen()
elseif mode == "reset" then
    -- Reset password functionality
    local newPassword = tArgs[2]
    if newPassword then
        if setPassword(newPassword) then
            print("Password reset successful.")
        else
            print("Error resetting password.")
        end
    else
        print("Usage: reset newpassword")
    end
elseif mode == "encrypt" then
    encryptSystem()
else
    print("Invalid mode. Supported modes: decrypt, reset, encrypt")
end