ModemAPI

local channel = 0
local modem


function setModem(side)
    modem = peripheral.wrap(side)
end

function setChannel(ch)
    channel = ch
end

function openModem(ch)
    ch = ch or channel
    if not modem.isOpen(ch) then
        modem.open(ch)
        print("Opened modem: " .. ch)
    else
        print("Modem already opened: " .. ch)
    end
end

function closeModem(ch)
    ch = ch or channel
    if modem.isOpen(ch) then
        modem.close(ch)
        print("Closed modem: " .. ch)
    else
        print("Modem already closed: " .. ch)
    end
end

function modemSetup(side, ch)
    modem = peripheral.wrap(side)
    setChannel(ch)
    openModem()
end

function sendMessage(msg, ch, returnCh)
    ch = ch or channel
    returnCh = returnCh or channel

    if type(msg) == "table" then
        msg = textutils.serialize(msg)
    end

    modem.transmit(ch, returnCh, msg)
end


function waitForMessage(ch, timeout)
    ch = ch or channel
    local myTimer
    if timeout then
        myTimer = os.startTimer(timeout)
    end
    while true do
        local event, par1, senderChannel,
        replyChannel, message, senderDistance = os.pullEvent()

        if event == "timer" and par1 == myTimer then
            print("message timeout")
            return false
        end

        if senderChannel == ch then
            return true, message, replyChannel
        end
    end
end

function sendAndWaitForResponse(msg, ch, returnCh, timeout)
    sendMessage(msg, ch, returnCh)

    local worked, message, replyChannel = waitForMessage(returnCh, timeout)
    return worked, message, replyChannel
end