3x3 tunnel with torches

-- 3x3 Tunnel digger script for ComputerCraft turtle by Scott 'Satscape' Hather - www.satscape.info
-- Place the turtle at the front left of where you want the 3x3xinfinte tunnel (and facing it)
-- Place a chest directly behind it
-- Place torches in the bottom right slot (one stack will last 640 metres)
-- Place coal/lava etc in first slot
-- It will empty itself into the chest at regular intervals and embed torches in the tunnel walls! (only works with latest CC - requires modifying to work with turtles with 9 slots)

if turtle.getItemCount(16) == 0 then
    print("Place some torches in the last slot");
    os.sleep(10);
    os.reboot();
end

if turtle.getFuelLevel()==0 then
    turtle.select(1);
    local ok=turtle.refuel();
    if not ok then
        print("Place some fuel into first slot");
        os.sleep(10);
        os.reboot();
    end
end

distanceFromChest=0;
distanceWere=0;

function digAndMove()
    while (turtle.detect()) do
        turtle.dig(); os.sleep(1);
    end
    turtle.forward();
end

function digAndMoveUp()
    while (turtle.detectUp()) do
        turtle.digUp(); os.sleep(1);
    end
    turtle.up();
end

while (turtle.getItemCount(16) >0) do
    print("Diggy Diggy hole, got "..turtle.getFuelLevel().." fuel left.");
    distanceFromChest=distanceFromChest + 1;
    digAndMove(); -- bottom left
    turtle.turnRight();
    digAndMove(); -- bottom centre
    digAndMove(); -- bottom right
    turtle.turnLeft();
    digAndMoveUp(); -- centre right
    turtle.turnLeft();
    digAndMove(); -- centre centre
    digAndMove(); -- centre left

    if distanceFromChest % 10 == 1 then
        turtle.dig();
        turtle.select(16);
        turtle.place(); -- place the torch embedded in tunnel
    end

    turtle.turnRight();
    digAndMoveUp(); -- top left
    turtle.turnRight();
    digAndMove();  -- top centre
    digAndMove(); -- top right

    turtle.turnLeft();
    turtle.turnLeft();
    turtle.forward(); turtle.forward();
    turtle.turnRight();
    turtle.down();
    turtle.down();

    if distanceFromChest % 50 ==0 then  -- time to empty our stuff
        distanceWere=distanceFromChest;
        turtle.turnLeft(); turtle.turnLeft();
        while distanceFromChest > 0 do
            turtle.forward();
            distanceFromChest = distanceFromChest - 1;
        end
        os.sleep(1);
        for slot=1, 15, 1 do
            turtle.select(slot);
            turtle.drop();
        end
        os.sleep(1);
        turtle.turnLeft(); turtle.turnLeft();
        while distanceWere > 0 do
            turtle.forward();
            distanceWere = distanceWere - 1;
            distanceFromChest = distanceFromChest + 1;
        end
    end
end
print("Ending tunnel2 script");
os.sleep(10);
os.reboot(); -- reboots until you place torches in last slot