mine

tdeep=50
function mainProg()
  print(turtle.getFuelLevel())
  for i=3,7 do
    if turtle.getFuelLevel()>(tdeep*2+2+i*4+50) then
      goUp(i*2)
      digTwinTunnel(tdeep)
      turtle.turnRight()
      goForward()
      turtle.turnRight()
      goUp(-i*2)
      unloadTurtle()
    end
  end
  print(turtle.getFuelLevel())
end

function unloadTurtle()
  print("Dropping items...")
  turtle.turnLeft()
  turtle.turnLeft()
  for c=1,16 do
    turtle.select(c)
    if turtle.getItemCount(c)>0 then
      turtle.drop(turtle.getItemCount(c))
    end
  end
  turtle.turnLeft()
  turtle.turnLeft()
end

function cargoInfo()
  for c=1,16 do
    print(turtle.getItemCount(c))
  end
end

function mineBit()
  while turtle.detect() do
    turtle.dig()
    sleep(0.5)
  end
  while turtle.detectUp() do
    turtle.digUp()
    sleep(0.5)
  end
end

function goForward()
  while turtle.detect() do
    turtle.dig()
    sleep(0.5)
  end
  turtle.forward()
end

function goUp(n)
  if n<0 then
    for i=1,-n do
      while turtle.detectDown() do
        turtle.digDown()
      end
      turtle.down()
    end
  else
    for i=1,n do
      while turtle.detectUp() do
        turtle.digUp()
        sleep(0.5)
      end
      turtle.up()
    end
  end
end

function goDown(n)
  for i=1,n do
    while turtle.detectDown() do
      turtle.digDown()
      sleep(0.5)
    end
    turtle.down()
  end
end

function digSingleTunnel(tdepth)
  for i=1,tdepth do
    mineBit()
    goForward()
  end

  turtle.turnLeft()
  turtle.turnLeft()

  for i=1,tdepth do
    goForward()
  end
end

function digTwinTunnel(depth)
  for I=1,depth do
    mineBit()
    goForward()
  end
  turtle.turnRight()
  mineBit()
  goForward()
  turtle.turnRight()
  for I=1,depth do
    mineBit()
    goForward()
  end
end

mainProg()