EnergyMonitor/server/monitorReceiver.lua

-- user options
local options = {
    timeout = 15,
    scale = 2,
}


-- clear terminal to start
term.clear()

-- system options/components
local system = {}


-- initialize ender modem
function init_modem()
    local modem = peripheral.find('modem')
    system.modem = modem
end
init_modem()

-- initialize monitor
function init_monitor()
    local monitor = peripheral.find('monitor')
    -- redirect output to monitor
    term.redirect(monitor)
    term.clear()
    term.setCursorPos(1, 1)

    -- set text scale on monitor
    monitor.setTextScale(options.scale)

    -- save monitor and width
    system.monitor = monitor
    system.width = term.getSize()
end
init_monitor()

-- check whether channel is already in use and negate output
function channel_used(channel)
    for _, value in pairs(system.channels) do
        if value == channel then
            return true
        end
    end
    return false
end

-- wait for components to connect to receiver
function wait_for_components()
    -- reset system variables
    system.timeout = false
    system.components = {}
    system.channels = {}
    system.index = 1

    -- open initializer channel
    system.modem.open(1)
    print('Waiting for components...')
    print('Continue by clicking.')

    local count = 0
    while true do
        -- get next pull event
        local event, _, senderChannel, replyChannel, message, _ = os.pullEvent()

        local component = ''
        local success = false
        -- reply to channel 1 (initializer) only
        if event == 'modem_message' and senderChannel == 1 then
            -- component is trying to connect
            if channel_used(replyChannel) then
                system.modem.transmit(replyChannel, replyChannel, 'used')
            else
                -- save component
                table.insert(system.channels, replyChannel)
                table.insert(system.components, message)

                component = message
                count = count + 1
                success = true
            end
        elseif event == 'monitor_touch' and count > 0 then break end

        -- reply with successful connection
        if success then
            system.modem.transmit(replyChannel, replyChannel, 'ready ' .. system.width)
            -- open channel for communication
            system.modem.open(replyChannel)
            print(component .. ' connected!')
        end
    end

    -- reset terminal
    term.clear()
    term.setCursorPos(1, 1)

    -- close initializer channel
    system.modem.close(1)
end
wait_for_components()

function display_messages(buffer)
    print(table.concat(buffer, '\n'))
end

function add_message(buffer, text)
    table.insert(buffer, text)
end

function get_messages(buffer)
    -- get component data
    local index = system.index
    local channel = system.channels[index]
    local component = system.components[index]

    -- pad the index with leading zeroes for display
    local length = #tostring(index)
    local amount = #tostring(#system.components)
    local padded = string.rep('0', #tostring(amount - length)) .. index

    -- add component as title
    table.insert(buffer, '#' .. padded .. ' ' .. component .. ':')

    -- request data and measure elapsed time
    local timer_id = os.startTimer(options.timeout)
    system.modem.transmit(channel, channel, 'print')

    -- keep track of exit condition
    local touchExit = false
    while true do
        -- get next pull event
        local event, _, senderChannel, _, message, _ = os.pullEvent()
        if event == 'modem_message' then
            -- save message in buffer
            if senderChannel == channel then
                table.insert(buffer, message)
                system.modem.transmit(channel, channel, 'ok')
                break
            -- dont accept messages from wrong channel
            else system.modem.transmit(senderChannel, senderChannel, 'busy') end
        elseif event == 'timer' then
            system.timeout = true
            return
        elseif event == 'monitor_touch' then
            touchExit = true
        end
    end

    -- cancel timer on success
    os.cancelTimer(timer_id)

    -- increment index and clear terminal on exit by touch
    if touchExit then
        term.clear()
        system.index = system.index % #system.components + 1
        return false
    end

    return true
end

-- main program
function main()
    -- permanent runtime
    while true do
        term.clear()

        system.test = true
        while not system.timeout do
            -- print over old values
            term.setCursorPos(1, 1)

            local buffer = {}
            if get_messages(buffer) then display_messages(buffer) end
        end

        -- reset terminal
        term.clear()
        term.setCursorPos(1, 1)
        print('Component disconnected!')
        print('Rescanning . . . ')

        -- rescan components
        wait_for_components()
    end
end
main()