Doggy OS RedNet message decoder

-- RedNet Decoder with Enhanced Info, Auto Decrypt & Auto Save to One File
local modemSide = "top" -- Change to the side where your modem is connected
rednet.open(modemSide)

-- Global settings
local settings = {
    autoSave = false,   -- Auto save decrypted messages
    autoDecrypt = false -- Auto decrypt incoming RedNet messages
}

-- Define the default key file for auto decryption
local defaultKeyFile = "decryption_key.txt" -- The key file for auto-decrypt
local decryptedMessagesFile = "decrypted_messages.txt" -- The file where all messages will be saved

-- Function to read the decryption key from a file
local function readKeyFromFile(fileName)
    if not fs.exists(fileName) then
        error("File does not exist: " .. fileName)
    end
    local file = fs.open(fileName, "r")
    local key = file.readAll()
    file.close()
    return key:gsub("%s+", "") -- Trim whitespace
end

-- Function to decrypt a message using XOR
local function decryptMessage(encryptedMessage, key)
    local decryptedMessage = ""
    local encryptionKey = {} -- Store the encryption key for display
    for i = 1, #encryptedMessage do
        local encChar = string.byte(encryptedMessage:sub(i, i))
        local keyChar = string.byte(key:sub(((i - 1) % #key) + 1))
        decryptedMessage = decryptedMessage .. string.char(bit.bxor(encChar, keyChar))
        table.insert(encryptionKey, keyChar) -- Store the XOR key characters
    end
    return decryptedMessage, encryptionKey
end

-- Function to auto save the decrypted message to a single file
local function autoSaveMessage(decryptedMessage, senderId)
    if settings.autoSave then
        local timestamp = os.date("%Y-%m-%d_%H-%M-%S")
        local file = fs.open(decryptedMessagesFile, "a") -- Open file in append mode
        file.write("\n--------------------------------------------------\n")
        file.write("Timestamp: " .. os.date("%Y-%m-%d %H:%M:%S") .. "\n")
        file.write("Sender ID: " .. senderId .. "\n")
        file.write("Decrypted Message: " .. decryptedMessage .. "\n")
        file.write("--------------------------------------------------\n")
        file.close()
        print("Message saved automatically to", decryptedMessagesFile)
    end
end

-- Function to handle RedNet messages
local function handleRedNetMessages()
    print("\n--------------------------------------------------")
    print("Waiting for a RedNet message... Press 'q' to quit.")
    print("--------------------------------------------------\n")

    while true do
        local senderId, encryptedMessage = rednet.receive()

        -- Show detailed information about the message
        print("\n--------------------------------------------------")
        print("Encrypted message received from ID:", senderId)
        print("Timestamp: " .. os.date("%Y-%m-%d %H:%M:%S"))
        print("Encrypted Message: " .. encryptedMessage)
        print("--------------------------------------------------\n")

        -- Handle decryption
        local decryptedMessage
        local keyFileUsed
        local encryptionKey

        if settings.autoDecrypt then
            -- Use the predefined key file for decryption
            local key
            local success, err = pcall(function()
                key = readKeyFromFile(defaultKeyFile)
            end)
            if not success then
                print("Error reading key:", err)
                return
            end
            decryptedMessage, encryptionKey = decryptMessage(encryptedMessage, key)
            keyFileUsed = defaultKeyFile
            print("Decrypted Message: " .. decryptedMessage)
        else
            -- If autoDecrypt is off, ask for file name
            print("Auto Decrypt is disabled. Please enter the key file name for decryption:")
            local keyFileName = read()
            local key
            if fs.exists(keyFileName) then
                key = readKeyFromFile(keyFileName)
                decryptedMessage, encryptionKey = decryptMessage(encryptedMessage, key)
                keyFileUsed = keyFileName
                print("Decrypted Message: " .. decryptedMessage)
            else
                print("Error: Key file does not exist.")
                return
            end
        end

        -- Show additional information after decryption
        print("\n--------------------------------------------------")
        print("Decryption Complete:")
        print("Original Encrypted Message: " .. encryptedMessage)
        print("Decrypted Message: " .. decryptedMessage)
        print("Sender ID: " .. senderId)
        print("Timestamp: " .. os.date("%Y-%m-%d %H:%M:%S"))
        print("Decryption Key File Used: " .. keyFileUsed)
        print("Encryption Key Used: " .. table.concat(encryptionKey, ", "))
        print("--------------------------------------------------\n")

        -- Auto Save if enabled
        autoSaveMessage(decryptedMessage, senderId)
    end
end

-- Main Settings Menu for configuring options
local function settingsMenu()
    while true do
        print("\n--------------------------------------------------")
        print("Settings Menu:")
        print("1. Toggle Auto Save (Currently: " .. (settings.autoSave and "On" or "Off") .. ")")
        print("2. Toggle Auto Decrypt (Currently: " .. (settings.autoDecrypt and "On" or "Off") .. ")")
        print("3. Set Decryption Key File (Current: " .. defaultKeyFile .. ")")
        print("4. Back to Main Menu")
        print("--------------------------------------------------")
        print("Select an option (1-4):")
        local choice = tonumber(read())

        if choice == 1 then
            settings.autoSave = not settings.autoSave
            print("Auto Save is now " .. (settings.autoSave and "enabled" or "disabled"))
        elseif choice == 2 then
            settings.autoDecrypt = not settings.autoDecrypt
            print("Auto Decrypt is now " .. (settings.autoDecrypt and "enabled" or "disabled"))
        elseif choice == 3 then
            print("Enter the new decryption key file path:")
            defaultKeyFile = read()
            print("Decryption key file is now set to: " .. defaultKeyFile)
        elseif choice == 4 then
            break
        else
            print("Invalid choice, please try again.")
        end
    end
end

-- Main Menu for navigating the program
local function mainMenu()
    while true do
        print("\n--------------------------------------------------")
        print("RedNet Decoder Main Menu")
        print("1. Start RedNet - Receive and Decode Messages")
        print("2. Settings - Configure Auto Save and Auto Decrypt")
        print("3. Exit")
        print("--------------------------------------------------")
        print("Please select an option (1-3):")
        local choice = tonumber(read())

        if choice == 1 then
            handleRedNetMessages()
        elseif choice == 2 then
            settingsMenu()
        elseif choice == 3 then
            print("Exiting program...")
            break
        else
            print("Invalid choice, please try again.")
        end
    end
end

-- Run the main menu
mainMenu()

rednet.close()
print("RedNet Decoder has stopped.")