-- host.lua

-- Function to find and open the modem
local function openModem()
    local sides = {"left", "right", "top", "bottom", "front", "back"}
    for _, side in ipairs(sides) do
        if peripheral.isPresent(side) and peripheral.getType(side) == "modem" then
            rednet.open(side)
            return true
        end
    end
    return false
end

-- Open the modem
if not openModem() then
    print("No modem found!")
    return
end

local pairedClients = {}

-- Function to send command to a specific client
local function sendCommand(pairingKey, command)
    local clientId = pairedClients[pairingKey]
    if clientId then
        rednet.send(clientId, command, "command")
        local senderId, response, protocol = rednet.receive("response")
        if senderId == clientId then
            print("Response from client " .. clientId .. ": " .. response)
        else
            print("Unexpected response from client " .. senderId)
        end
    else
        print("No client paired with this key.")
    end
end

-- Function to pair with a new client
local function pairClient(pairingKey)
    print("Waiting for client with key " .. pairingKey)
    local senderId, receivedKey, protocol = rednet.receive("pairing", 30)
    if protocol == "pairing" and receivedKey == pairingKey then
        pairedClients[pairingKey] = senderId
        print("Paired with client " .. senderId .. " using key " .. pairingKey)
    else
        print("Pairing failed or timed out.")
    end
end

-- Main loop
while true do
    print("Enter command (pair, send): ")
    local action = read()
    if action == "pair" then
        print("Enter pairing key (4-digit hex): ")
        local pairingKey = read()
        pairClient(pairingKey)
    elseif action == "send" then
        print("Enter pairing key: ")
        local pairingKey = read()
        print("Enter command: ")
        local command = read()
        sendCommand(pairingKey, command)
    else
        print("Invalid command.")
    end
end