-- Offset from the left
-- Will be set at bottom of code
offset = 0

-- How far forward the turtle has gone
distance = 0

turtle.turnAround = function()
	turtle.turnRight()
  turtle.turnRight()
end

function forwardButWait(dist)
	-- Go forward the given distance, but wait for other things to get out of the way
  local goal = dist
  while goal > 0 do
  	if turtle.forward() then
    	goal = goal - 1
    end
  end
end

function forwardAndMine(dist)
	-- Go forward the given distance, mining things in the way
  local goal = dist
  while goal > 0 do
  	turtle.dig()
    if turtle.forward() then
    	goal = goal - 1
    end
  end
end

function pitstop()
  turtle.turnAround()
  forwardAndMine(distance)

	turtle.turnRight()
  forwardButWait(offset)

  turtle.turnLeft()
  for i=1,16 do
  	turtle.select(i)
    turtle.drop()
  end
  turtle.turnRight()

  turtle.suck()
  turtle.refuel()
  turtle.turnAround()
  forwardButWait(offset)

  turtle.forward()
  offset = offset + 1
  distance = 0

  turtle.turnLeft()
end

function invfull()
	for i=1,16 do
  	if turtle.getItemCount(i) == 0 then
    	return false
    end
  end
  return true
end

function check()
	print("Fuel: " .. tostring(turtle.getFuelLevel()))
	if (turtle.getFuelLevel() <= distance + offset) or invfull() then
  	print("Going for a pitstop!")
  	pitstop()
  end
end

function mine()
	while true do
    check()
    turtle.dig()
    turtle.digUp()
    turtle.digDown()
    if turtle.forward() then
    	distance = distance + 1
    end
  end
end

print("Mining begun.")

turtle.refuel()
while turtle.back() do end
turtle.turnLeft()
while turtle.forward() do end
turtle.suck()
turtle.refuel()

print("Initial refuel done.")

turtle.turnAround()
while not turtle.detect() do
	offset = offset + 1
  turtle.forward()
end
turtle.dig()
turtle.forward()
offset = offset + 1
turtle.turnLeft()

print("Offset is " .. tostring(offset) .. ".")

mine()