Printron Server

local m = peripheral.find "modem"
local o = peripheral.find "monitor"
local p = peripheral.find "printer"

local log_channel, job_channel = 404, 1337

o.setCursorPos(1, 1)
o.clear()
o.setTextScale(0.5)

m.open(job_channel)

local function log(msg)
    m.transmit(log_channel, job_channel, msg)
    local last_term = term.redirect(o)
    if type(msg) == "string" then print(msg) end
    term.redirect(last_term)
end

local function make_printer_terminal(printer)
    local function stub() end

    local title = ""

    local printerTerminal = {
        getCursorPos = printer.getCursorPos,
        getSize = printer.getPageSize,
        write = printer.write,
        isColor = function() return false end,
        isColour = function() return false end,
        blit = stub,
        clear = stub,
        clearLine = stub,
        setCursorBlink = stub,
        setTextColor = stub,
        setBackgroundColor = stub,
        getBackgroundColor = function() return colors.white end,
        getTextColor = function() return colors.black end
    }

    function printerTerminal.setCursorPos(x, y)
            local w, h = printer.getPageSize()
            if y > (h + 1) then printerTerminal.scroll() y = y - h end
            printer.setCursorPos(x, y)
    end

    function printerTerminal.makePage()
        while not printer.newPage() do
            if printer.getPaperLevel() < 1 then
                log "Add more paper."
            end
            if printer.getInkLevel() < 1 then
                log "Add more ink."
            end

            log "Hit any key on print server when done."
            os.pullEvent "key"
        end
        printer.setPageTitle(title)
    end

    function printerTerminal.finishPage()
        log "Clear output tray."

        while not printer.endPage() do
            sleep(1)
        end
    end

    function printerTerminal.scroll()
        printerTerminal.finishPage()
        printerTerminal.makePage()
    end

    function printerTerminal.setPageTitle(t)
        title = t
    end

    return printerTerminal
end

local queue = {}

local function do_printy_stuff()
    local pterm = make_printer_terminal(p)
    while true do
        local job
        repeat
            job = table.remove(queue, 1)
            sleep(1)
        until job ~= nil

        job.title = job.title or "Untitled"

        term.redirect(pterm)
        log { type = "job_running" }
        pterm.makePage()
        log(string.format("Printing %d chars for job %s.", #job.text, job.title))
        pterm.setPageTitle(job.title)
        print(job.text)
        pterm.finishPage()
        log "Printing complete."
        log { type = "job_complete" }
    end
end

local function respond_to_commands()
    while true do
        local _, _, chan, reply_chan, message = os.pullEvent "modem_message"

        if chan == job_channel and reply_chan == log_channel and type(message) == "table" and message.text and message.title then
            log { type = "job_starting" }
            table.insert(queue, message)
        else
            print "Ignoring invalid message."
        end
    end
end

local function handle_terminate()
    os.pullEventRaw "terminate"
    log "Print job manually terminated."
    log { type = "job_complete" }
end

parallel.waitForAny(respond_to_commands, do_printy_stuff, handle_terminate)