Computercraft/Tanks

-- Valve, Monitor & Wireless Modem
local tank = peripheral.wrap("back")
local mon = peripheral.wrap("top")
local wmod = peripheral.wrap("bottom")

-- Make sure channel/frequency match main computer

local sendFreq = 2       -- Modem "Frequency"
local warning = 30       -- Warning level in %
local cap                -- Tank capacity
local amount             -- Amount liquid in tank
local percentfull        -- Percent liquid in tank
local sleeptime          -- How long to sleep
local sendpercent        -- Formatted percentage string
monX,monY = mon.getSize()

-- Set warning lamp to off
redstone.setOutput("right", false)

function getTank(tank)
    local output = tank.getTanks() -- Local to the getTank function.

    fluidName = output[1]["displayName"]
    fluidAmount = output[1]["amount"]
    fluidCapacity = output[1]["capacity"]

    return fluidName, fluidAmount, fluidCapacity -- Returning the values of global variables (which are nil).
end

-- Main prog loop, never stop
while true do
  wmod.open(2)
  mon.clear()
  mon.setCursorPos(1,1)

  -- Fill table with data from tank valve
  local fluidName, fluidAmount, fluidCapacity = getTank(tank)

  if fluidName then
    -- Get values for tank capacity and amount
    cap = fluidCapacity / 1000
    am = fluidAmount

    -- If tank is empty, to avoid math issues with 0
    if am == nil then
      am = 0
      percentfull = 0
    else
      -- Use math.floor to convert to integers
      am = math.floor(am / 1000)
      percentfull = math.floor(100 * am / cap)
    end

    -- Self explanatory :)
    mon.write("Fluid :" ..fluidName)
    mon.setCursorPos(1,2)
    mon.write("Amount: " ..am .."/"..cap .." B.")
    mon.setCursorPos(1,3)
    mon.write("Percent: " ..percentfull .."%  ")

    --Transmition Zone
    tankw = {water = percentfull}
    wmod.transmit(2,2,tankw)
    print("Current Percent :"..tankw["water"])

    --Warning Zone
    mon.setCursorPos(1,4)
    if percentfull < warning then
      redstone.setOutput("right", true)
      mon.write("Less than " ..warning .."% full")
      sleeptime = 1
    else
      -- Above warning level, sleep longer
      mon.write("More than " ..warning .."% full")
      redstone.setOutput("right", false)
      sleeptime = 10
    end
  else
    -- If no liquid is found in tank..
    mon.write("No liquid in tank")
    percentfull = 0
    term.clear()
    term.setCursorPos(1,1)
    print("No liquid in tank")
    sleeptime = 10
    percentfull = 0
    tankw = {water = percentfull}
    wmod.transmit(2,2,tankw)
    print("Current Percent :"..tankw["water"])
  end
    -- Sleep either 1 or 10 seconds
  sleep(sleeptime)
end