CC: Miner Filler

-- Turtle Program for digging and filling in tunnels

blocks = {1,1,1,2}

doBoth = false
digging = false
finished = false
index = 1

function refuel ()
    -- Refuel from the last slot if we are low
    if turtle.getFuelLevel() < 10 then
        i = turtle.getSelectedSlot()
        turtle.select(16)
        turtle.refuel()
        turtle.select(i)
    end
end

-- Setup main variables based on user input
function setup ()
    print("Are we digging [dig], filling [fill], or both [both]?")
    op = read()
    responses = {["dig"] = true, ["fill"] = true, ["both"] = true}
    if (responses[op] ~= true) then
        print("Invalid response.")
        return false
    elseif (op == "dig") then
        digging = true
    elseif (op == "fill") then
        digging = false
        setupOffset()
    elseif (op == "both") then
        digging = true
        doBoth = true
        setupOffset()
    end

    return true
end

-- Setup for the offset variable
function setupOffset ()
    print("Enter offset in blocks list: ")
    op = read()
    current = tonumber(op)
end

function main ()
    refuel()

    if digging then
        -- If we have reached an air block, finish digging phase
        if (turtle.inspect() == false) then
            digging = false
            if not doBoth then
                finished = true
            end
            return
        end

        turtle.dig()
        turtle.forward()
    else -- If Filling
        if (turtle.back()) then
            turtle.select(blocks[current])
            turtle.place()

            current = (current % table.getn(blocks)) + 1
        else -- Can't move back, finish fill phase
            finished = true
        end
    end
end

if (setup()) then
    while (not finished) do
        main ()
    end

    print("Finished Operation")
end