Railcraft tank builder

tankSize = 3*3
tankHeight = 4

function refill(targetSlot, targetItems, fromSlot, toSlot)
    if turtle.getItemCount( targetSlot )<targetItems then
        for i=fromSlot, toSlot do
            if turtle.getItemCount ( i )~=0 then
                turtle.select( i )
                turtle.transferTo(targetSlot, turtle.getItemCount ( i ))

                if turtle.getItemCount( targetSlot )>=targetItems then
                    turtle.select(targetSlot)
                    return true
                end
            end
        end
    else
        return true
    end

    turtle.select(targetSlot)
    return false --if not enough items in the targetSlot
end

function countItemsInSlots(fromSlot, toSlot)
    local count = 0
    for i = fromSlot, toSlot do
        count = count + turtle.getItemCount(i)
    end

    return count
end

function enoughIronTankWallBlocks()
    if countItemsInSlots(1,4) < frameBlocks + lidBlocks then
        print("I don't have enough 'Iron Tank Wall' blocks!")
        print("I need ".. (frameBlocks + lidBlocks) - countItemsInSlots(1,4) .." more blocks!")
        return false
    end
    return true
end

function enoughIronTankGaugeBlocks()
    if countItemsInSlots(5,8) < sideBlocks then
        print("I don't have enough 'Iron Tank Gauge' blocks!")
        print("I need ".. (sideBlocks) - countItemsInSlots(5,8) .." more blocks!")
        return false
    end
    return true
end

function enoughBlocks()
    return (enoughIronTankWallBlocks() and enoughIronTankGaugeBlocks())
end

function OddOrEven(num, odd, even)
    if num%2 == 1 then
        return odd
    end
    return even
end

function even(num)
    return num%2 == 0
end

tankSize = math.sqrt(tankSize)

function calculateSideBlocks()
    return (tankSize - 2) * (tankHeight - 2) * 4
end

function calculateLids()
    return (tankSize - 2)^2 * 2
end

function calculateFrame()
    return (tankHeight - 2) * 4 + (tankSize - 2) * 8 + 8
end

frameBlocks = calculateFrame()
sideBlocks = calculateSideBlocks()
lidBlocks = calculateLids()

print("Tank size: "..tankSize.." | Tank height: "..tankHeight)
print("Frame: " ..frameBlocks.. " blocks")
print("Side: " ..sideBlocks.. " blocks")
print("Lids: " ..lidBlocks.. " blocks")
print("Total volume: ".. tankSize * tankHeight * tankSize * 16 .."mB")
sleep(1)
print("\nPut ".. frameBlocks + lidBlocks .." 'Iron Tank Wall' blocks in slots 1-4")
print("Put ".. sideBlocks .." 'Iron Tank Gauge' blocks in slots 5-8")

print("\nPress Enter to continue")
while true do
    local event, key = os.pullEventRaw("key")
    if key == 28 then -- Enter
        break
    elseif key == 211 or key == 14 then -- Delete
        print("Exit...")
        error()
    end
end

enoughBlocks()
while true do --true is necessary
    print("\nPress Enter to count blocks again")
    local event, key = os.pullEvent("key")
    if key == 28 then -- Enter
        if enoughBlocks() then break end
    elseif key == 211 or key == 14 then -- Delete
        print("Exit...")
        error()
    end
end

print("\n\n\n\n\n\n\n\n\n\nI have enough blocks, starting building the "..tankSize.."x"..tankHeight.."x"..tankSize.." tank!")

function buildRow(buildDirection, moveDirection)
    for z = 1, tankSize do
        turtle[buildDirection]()
        if z~= tankSize then turtle[moveDirection]() end --dont outbreak from border
    end
end

function buildSurface(slot)
    turtle.select(slot)

    for x = 1, tankSize do
        buildRow("placeDown", OddOrEven(x, "forward", "back")) --switch movement direction every iteration
        if x ~= tankSize then
            turtle.turnRight()
            turtle.forward()
            turtle.turnLeft()
            refill(slot, 32, slot + 1, slot + 3)
        end
    end
end

function buildColumn(slot, buildDirection, moveDirection)
    turtle.select(slot)

    for y = 2, tankHeight - 2 do --1 block is already below us, the top will be built later
        turtle[moveDirection]()
        turtle[buildDirection]()
        refill(slot, 32, slot + 1, slot + 3)
    end
end

function buildWall(stay)
    buildColumn(1, "placeDown", "up")
    turtle.turnRight()

    for z = 2, tankSize - 1 do
        turtle.turnLeft()
        turtle.back()
        turtle.place()
        turtle.turnRight()
        buildColumn(5, OddOrEven(z, "placeDown", "placeUp"), OddOrEven(z, "up", "down"))
    end
    if not stay then --nil or false
        --place a block where the turtle currently is and move to block on the right
        turtle.turnLeft()
        turtle.back()
        turtle.place()
        turtle.turnRight()
    end
end

function buildTank()
    buildSurface(1)

    buildWall()
    buildWall()
    buildWall()

    buildWall(true)
    --go to the top
    turtle.back()
    turtle.place()
    for i = 2, tankHeight do
        turtle.up()
    end
    turtle.forward()
    turtle.turnRight()
    turtle.forward()
    turtle.turnRight()

    buildSurface(1)
end

buildTank()