-- XOR encryption function for message security
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 receiving messages from the server
local function handleIncomingMessages(protocol, encryptionKey)
    while true do
        local senderId, encryptedMessage, receivedProtocol = rednet.receive(protocol)
        if receivedProtocol == protocol then
            local decryptedMessage = xorEncryptDecrypt(encryptedMessage, encryptionKey)
            print(decryptedMessage)
        end
    end
end

-- Function to send messages to the server
local function sendMessageToServer(protocol, username, encryptionKey)
    while true do
        print("[" .. protocol .. "] Type your message (or 'exit' to leave): ")
        local message = read()
        if message == "exit" then
            print("Leaving chatroom...")
            break
        end

        local formattedMessage = username .. ": " .. message
        local encryptedMessage = xorEncryptDecrypt(formattedMessage, encryptionKey)
        rednet.broadcast(encryptedMessage, protocol)
    end
end

-- Function to connect to the server and join the chatroom with password
local function connectToChatroom(protocol, username)
    print("Attempting to join chatroom with protocol: " .. protocol)

    -- Get the password to access the chatroom
    print("Enter the password for this chatroom: ")
    local password = read("*")

    -- Send the password to the server for verification
    rednet.broadcast(password, protocol .. "-password")

    -- Wait for password validation result
    local senderId, validationResponse = rednet.receive(protocol .. "-password-response")

    if validationResponse == "success" then
        print("Password accepted. Joining chatroom...")

        -- Get the encryption key from the server
        rednet.broadcast("request-key", protocol .. "-key-request")
        local senderId, encryptionKey = rednet.receive(protocol .. "-key-response")

        -- Start sending and receiving messages
        parallel.waitForAny(
            function() handleIncomingMessages(protocol, encryptionKey) end,
            function() sendMessageToServer(protocol, username, encryptionKey) end
        )
    else
        print("Incorrect password. Access denied.")
    end
end

-- Function to list available modems
local function listModems()
    local modems = {}
    for _, side in ipairs(peripheral.getNames()) do
        if peripheral.getType(side) == "modem" then
            table.insert(modems, side)
        end
    end
    return modems
end

-- Function to set up the modem for communication
local function setupModem()
    local modems = listModems()
    if #modems == 0 then
        print("No modems found! Please attach a modem and restart.")
        return nil
    end

    print("Available modems:")
    for i, side in ipairs(modems) do
        print(i .. ": " .. side)
    end

    rednet.open(modems[1]) -- Open the first modem found
    print("Modem on " .. modems[1] .. " initialized.")
    return modems[1]
end

-- Main client function
term.clear()
term.setCursorPos(1, 1)

print("Welcome to the Protocol Private Chatroom Client")

-- Setup modem for client communication
local modemSide = setupModem()
if modemSide == nil then return end -- Exit if no modem found

-- Main loop to allow the user to join different chatrooms
while true do
    print("Enter a protocol to connect to a private chatroom (or 'exit' to quit): ")
    local protocol = read()

    if protocol == "exit" then
        print("Client shutting down...")
        break
    end

    if protocol ~= "" then
        print("Enter your username: ")
        local username = read()

        connectToChatroom(protocol, username)
    end
end