local modem = peripheral.find("modem")
local SERVER_PORT = 100
local CLIENT_PORT = 101

local function log(msg)
    print("[Server]: " .. tostring(msg))
end

local function broadcast(message)
    if modem then
        modem.transmit(CLIENT_PORT, SERVER_PORT, message)
    end
end

local function handleMessage(event, side, channel, replyChannel, message, distance)
    if type(message) == "table" then
        if message.type == "join" then
            log(message.username .. " connected.")
            broadcast({ type = "system", content = message.username .. " joined the chat." })
        elseif message.type == "leave" then
            log(message.username .. " disconnected.")
            broadcast({ type = "system", content = message.username .. " left the chat." })
        elseif message.type == "chat" then
            log(message.username .. ": " .. message.content)
            broadcast({ type = "chat", username = message.username, content = message.content })
        end
    end
end

local function listenLoop()
    if not modem then
        log("No modem found!")
        return
    end
    modem.open(SERVER_PORT)
    log("Listening on port " .. SERVER_PORT)
    
    while true do
        local eventData = {os.pullEvent("modem_message")}
        -- event, side, channel, replyChannel, message, distance
        if eventData[3] == SERVER_PORT then
            handleMessage(table.unpack(eventData))
        end
    end
end

local function main()
    parallel.waitForAll(listenLoop)
end

return { main = main }