Quarry

function refuel()
    --check inventory for fuel
    local maxFuel = 200

    --cycles through each slot refuelling
    --using everything in that slot
    --until full
    for i=3, 16 do
        if turtle.getFuelLevel() < maxFuel then
            turtle.select(i)
            turtle.refuel()
        end
    end

    --if not enough, use enderchest
    if turtle.getFuelLevel() < maxFuel then
        --select enderchest, place above
        while turtle.getItemCount(2) ~= 0 do
            turtle.select(2)
            turtle.placeUp()
            sleep(1)
        end

        --keep grabbing fuel until full
        while turtle.getFuelLevel() < maxFuel do
            if turtle.suckUp() == false then
                break --if no fuel available
                      --then stop refueling
            end
            turtle.refuel()
        end

        --replace enderchest
        turtle.digUp()
    end

    --reselect slot 1
    turtle.select(1)
end


function unload()
    --places enderchest above
    while turtle.getItemCount(1) ~= 0 do
        turtle.select(1)
        turtle.placeUp()
        sleep(1)
    end

    --dumps all items in chest
    for i=3, 16 do
        turtle.select(i)
        turtle.dropUp()
    end

    --reselects slot 1
    turtle.select(1)
    turtle.digUp() --gets enderchest back
end

function goFwd(dist)
local minFuel = 10

    for i=1, dist do
        --Refuel if needed
            if turtle.getFuelLevel() < minFuel then
        refuel()
        end

        --move + dig anything infront
        while not turtle.forward() do
            if turtle.getItemCount(16) > 0 then
                unload()
            end
            turtle.dig()
        end
    end
end


function digSquare(N)
    --digs an N*N square
    --dig square except last row
    for i=1, (N-1) do
        --on odd rows
        if i % 2 == 1 then
            goFwd((N-1))
            turtle.turnRight()
            goFwd(1)
            turtle.turnRight()
        else --on even rows
            goFwd((N-1))
            turtle.turnLeft()
            goFwd(1)
            turtle.turnLeft()
        end
    end

    --finish last row without the dig turn
    --turn so in bottom left of square
    goFwd((N-1))
    turtle.turnRight()
    if (N%2) == 1 then
        turtle.turnRight()
    end
end

function goDown()
    --checks for inv space
    if turtle.getItemCount(16) > 0 then
        unload()
    end

    --then goes down
    turtle.digDown()
    turtle.down()
end

function goUp(N)
    for i=1, N do
        --checks fuel
        if turtle.getFuelLevel < minFuel then
            refuel()
        end

        --checks for space
        if turtle.getItemCount(16) > 0 then
            unload()
        end

        while not turtle.up() do
            turtle.digUp()
        end
    end
end

function quarry(depth, size)
    for i=1, depth do
        goDown()
        digSquare(size)
    end
end

--need up function
--ACTUAL PROGRAM--

term.clear()
term.setCursorPos(1, 1)
print("Place item chest in slot 1")
print("and fuel chest in slot 2")
print("Then enter how far you would like to")
print("dig down")
local depth = read()
local depthNum = tonumber(depth)

print("Enter how big the square")
print("to dig should be")
local size = read()
local sizeNum = tonumber(size)

quarry(depthNum, sizeNum)