ComputerCraft - Turtle DigBorder

local blocksMovedSinceLastChestplace = 0
local chestSlot = 1 -- make sure to put this before fuelSlot, otherwise chests will be used for fuel
local fuelSlot = 2 -- fuel will not be checked for on any slot before this
local distanceBetweenChests = 100

-- Functions

function decidePlaceChest()
    if blocksMovedSinceLastChestplace >= distanceBetweenChests then
        local slotsFull = 0

        for i=1, 16, 1 do
            if i ~= torchSlot and i ~= chestSlot and i ~= fuelSlot then
                if turtle.getItemCount(i) > 0 then
                    slotsFull = slotsFull + 1
                end
            end
        end

        if slotsFull >= 7 then
            placeChest()
        end

        blocksMovedSinceLastChestplace = 0
    end
end

function placeChest()
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.select(chestSlot)

    if turtle.getItemCount(chestSlot) < 5 then
        setRed()
        print("Low on chests!")
    end

    turtle.select(chestSlot)
    while turtle.place() == false do
        turtle.dig()
        sleep(0.5)
    end

    for i=1, 16, 1 do
        if i ~= torchSlot and i ~= chestSlot and i ~= fuelSlot then
            turtle.select(i)
            turtle.drop()
        end
    end

    turtle.turnRight()
    turtle.turnRight()
end

function fuel()
    if turtle.getFuelLevel() < 5 then
        local alreadyNotified = false

        while true do
            local found = false

            for i=fuelSlot, 16, 1 do
                turtle.select(i)
                if turtle.refuel(1) == true then
                    found = true
                    break
                end
            end

            if found == true then
                break
            else
                if alreadyNotified == false then
                    print("Need fuel!")
                    alreadyNotified = true
                end
            end
        end
        turtle.select(1)
    end
end

function tryForward()
    local alreadyNotified = false
    fuel()
    while turtle.forward() == false do
        if alreadyNotified == false then
            print("Something is in my way!")
            alreadyNotified = true
        end
        turtle.dig()
        sleep(0.5)
    end
    blocksMovedSinceLastChestplace = blocksMovedSinceLastChestplace + 1
end
function tryUp()
    local alreadyNotified = false
    fuel()
    while turtle.up() == false do
        if alreadyNotified == false then
            print("Something is in my way!")
            alreadyNotified = true
        end
        turtle.digUp()
        sleep(0.5)
    end
    blocksMovedSinceLastChestplace = blocksMovedSinceLastChestplace + 1
end
function tryDown()
    local alreadyNotified = false
    fuel()
    while turtle.down() == false do
        if alreadyNotified == false then
            print("Something is in my way!")
            alreadyNotified = true
        end
        turtle.digDown()
        sleep(0.5)
    end
    blocksMovedSinceLastChestplace = blocksMovedSinceLastChestplace + 1
end

function digDistance(distance)
    for i=1, distance, 1 do
        digSingle()
        tryForward()
    end
end

function digSingle()
    while turtle.detect() == true do
        turtle.dig()
    end
    decidePlaceChest()
end
function digSingleUp()
    while turtle.detectUp() == true do
        turtle.digUp()
    end
    decidePlaceChest()
end

-- Scripts

local args = { ... }
-- or
if table.getn(args) ~= 3 then
    print("incorrect number of args")
    print("cleararea <length> <width> <height>")
    return
end
if args[1] == nil or args[2] == nil or args[3] == nil then
    print("nil arg")
    print("cleararea <length> <width> <height>")
    return
end
if tonumber(args[1]) == nil or tonumber(args[2]) == nil or tonumber(args[3]) == nil then
    print("NAN")
    print("cleararea <length> <width> <height>")
    return
end

local length = tonumber(args[1])
local width = tonumber(args[2])
local height = tonumber(args[3])
local newLength = length

for i=1, height, 1 do
    digDistance(newLength)
    newLength = length - 1
    turtle.turnRight()
    digDistance(width-1)
    turtle.turnRight()
    digDistance(length-1)
    turtle.turnRight()
    digDistance(width-1)
    turtle.turnRight()

    if i ~= height then
        tryDown()
    end
end

for i=1, height-1, 1 do
    tryUp()
end

turtle.back()

print("Complete")