-- Client-Side Code
local chatProtocol = ""  -- Custom protocol (ID entered by user)
local encryptionKey

-- Function to check if a file exists
local function fileExists(path)
    local file = fs.open(path, "r")
    if file then
        file.close()
        return true
    end
    return false
end

-- Function to download or create the XOR.key file
local function downloadOrCreateKey()
    local keyFilePath = "XOR.key"
    if fileExists(keyFilePath) then
        print("Encryption key found.")
    else
        print("Downloading encryption key...")
        local key = "x3A7rB8zD2L5qW4nH1"
        local file = fs.open(keyFilePath, "w")
        file.write(key)
        file.close()
        print("Encryption key saved as XOR.key.")
    end
    local file = fs.open(keyFilePath, "r")
    local key = file.readAll()
    file.close()
    return key
end

-- XOR encryption function
local function xorEncryptDecrypt(message, key)
    local encrypted = {}
    for i = 1, #message do
        local char = string.byte(message, i)
        local keyChar = string.byte(key, (i - 1) % #key + 1)
        table.insert(encrypted, string.char(bit.bxor(char, keyChar)))
    end
    return table.concat(encrypted)
end

-- Function to handle sending messages
local function sendMessage(username)
    while true do
        print("Type your message (or 'exit' to quit): ")
        local userInput = read()
        if userInput == "exit" then
            print("Exiting chat...")
            break
        end

        local formattedMessage = username .. ": " .. userInput
        local encryptedMessage = xorEncryptDecrypt(formattedMessage, encryptionKey)
        rednet.broadcast(encryptedMessage, chatProtocol)
        print("You: " .. userInput)
    end
end

-- Function to handle receiving messages
local function handleIncomingMessages()
    while true do
        local senderId, encryptedMessage, protocol = rednet.receive()
        if protocol == chatProtocol then
            local decryptedMessage = xorEncryptDecrypt(encryptedMessage, encryptionKey)
            local username, chatMessage = decryptedMessage:match("^(.-): (.+)$")
            if username and chatMessage then
                print("[" .. username .. "]: " .. chatMessage)
            else
                print("[Unknown User]: " .. decryptedMessage)
            end
        end
    end
end

-- Main program
term.clear()
term.setCursorPos(1, 1)

print("Welcome to the Doggy OS Network Chatroom!")
print("Enter the chatroom ID to connect:")
chatProtocol = read()

encryptionKey = downloadOrCreateKey()

rednet.open("top")  -- Open modem on front side to connect to the server
print("Connecting to chatroom ID: " .. chatProtocol)

print("Type 'exit' to leave the chat.")
parallel.waitForAny(
    function() handleIncomingMessages() end,
    function() sendMessage("User_" .. math.random(1000, 9999)) end
)