beacon[receiver]

-- =========================================================
-- beacon[receiver]
-- =========================================================
-- ----------------------------------------------------
-- Utilities
-- ----------------------------------------------------
function lFixText(text, length)
    return string.sub(text .. string.rep(" ", length), 1, length)
end
function rFixText(text, length)
    return string.sub(string.rep(" ", length) .. text, -length)
end
-- ----------------------------------------------------
-- Config
-- ----------------------------------------------------
local PROTOCOL_NAME = "BEACON"
local DISPLAY_INTERVAL = 1.5
local MODEM_DIRECTION = "back"
local LOST_COUNT = 5
-- =========================================================
-- beacon[receiver]
-- =========================================================
rednet.open(MODEM_DIRECTION)
local timerId = os.startTimer(DISPLAY_INTERVAL)
local dataTable = { }
while true do
    local rslt = { os.pullEvent() }
    if "modem_message" == rslt[1] then
        local event, side, frequency, replyFrequency, message, distance = rslt[1], rslt[2], rslt[3], rslt[4], rslt[5], rslt[6]
        if rednet.CHANNEL_BROADCAST == frequency then
            if nil ~= message and message.sProtocol == PROTOCOL_NAME then
                local dat = { }
                dat.id = replyFrequency
                dat.label = message.message
                dat.distance = distance
                dat.lostCount = LOST_COUNT
                if nil ~= dataTable[dat.id] then
                    dat.previousDistance = dataTable[dat.id].distance
                else
                    dat.previousDistance = -1
                end
                dataTable[dat.id] = dat
            end
        end
    elseif "timer" == rslt[1] then
        local event, tId = rslt[1], rslt[2]
        if timerId == tId then
            timerId = os.startTimer(DISPLAY_INTERVAL)
            term.clear()
            term.setCursorPos(1, 1)
            local signalCount = 0
            for key, dat in pairs(dataTable) do
                if 0 < dat.lostCount then
                    local tDist
                    if -1 == dat.distance then
                        tDist = "-----"
                    else
                        local distVal = math.floor(dat.distance * 10) / 10
                        if 0 == (distVal * 10) % 10 then
                            tDist = rFixText(tostring(distVal) .. ".0", 5)
                        else
                            tDist = rFixText(tostring(distVal), 5)
                        end
                    end
                    local noMove
                    if math.floor(dat.previousDistance * 10) == math.floor(dat.distance * 10) then
                        noMove = "?"
                    else
                        noMove = " "
                    end
                    local tId    = tostring(dat.id)
                    local tLabel = lFixText(dat.label, 20)
                    print(tDist .. noMove .. "[" .. tId .. "]" .. tLabel)
                    if LOST_COUNT == dat.lostCount then
                        signalCount = signalCount + 1
                    end
                end
                dat.lostCount = dat.lostCount - 1
                dat.previousDistance = dat.distance
                dat.distance = -1
            end
            if 0 == signalCount then
                print("No signal")
            end
        end
    end
end