Library code: Mining turtle

step = 0
term.clear()
term.setCursorPos(1, 1)
while true do
    if turtle.detect() then
        turtle.dig()
        if turtle.forward() then
            step = step +1
            turtle.digUp()
        end
    end
    itemCount = turtle.getItemCount(16)
    fuelLeft = turtle.getFuelLevel()
    if itemCount == 64 then
        while step > 0 do
            if turtle.back() then
                step = step - 1
            end
        end
        for i = 1, 16 do
            turtle.select(i)
            turtle.dropUp()
        end
        turtle.select(1)
        print('Bag Full')
        break
    elseif fuelLeft == step then
        while step > 0 do
            if turtle.back() then
                step = step - 1
            end
        end
        for i = 1, 16 do
            turtle.select(i)
            turtle.dropUp()
        end
        turtle.select(1)
        print('Out of fuel')
        break
    elseif turtle.detect() == false then
        while step > 0 do
            if turtle.back() then
                step = step - 1
            end
        end
        for i = 1, 16 do
            turtle.select(i)
            turtle.dropUp()
        end
        turtle.select(1)
        print('Reached opening')
        break
    end
end