simple spatial controller

local m = peripheral.find "modem"
local ioside = "bottom"
local io = peripheral.wrap(ioside)
local channel = 15216
local energy = 1.97e6
m.open(channel)

local function attempt_swap()
    if not io.getItemMeta(1) then return false, "no cell" end
    if io.getNetworkEnergyStored() < energy then return false, "insufficient energy" end
    rs.setOutput(ioside, true)
    sleep(0.2)
    rs.setOutput(ioside, false)
    return true
end

while true do
    local _, _, c, rc, msg = os.pullEvent "modem_message"
    if type(msg) == "table" and msg[1] == "swap" then
        local ok, err = attempt_swap()
        print("SWAP", ok, err)
        m.transmit(channel, channel, {"swapped", ok, err})
    elseif type(msg) == "table" and msg[1] == "ping" then
        m.transmit(channel, channel, {"pong"})
    end
end