mine

file = fs.open("Choords", "r")
c = textutils.unserialize(file.readAll())
file.close()

digging = true

blacklist = {"minecraft:grass", "minecraft:cobblestone", "minecraft:stone", "minecraft:dirt", "minecraft:gravel", "minecraft:sand"}

zDiff = {-1, 0, 1, 0}
xDiff = {0, 1, 0, -1}

function saveChoords()
  file = fs.open("Choords", "w")
  file.write(textutils.serialize(c))
  file.close()
end

function down()
  tryes = 0

  while not turtle.down() do
    turtle.digDown()

    tryes = tryes + 1

    if tryes > 5 then
      digging = false
      exitHole()
    end
  end

  c.y = c.y - 1

  saveChoords()
end

function forward()
  while not turtle.forward() do
    turtle.dig()
  end

  c.x = c.x + xDiff[c.o]
  c.z = c.z + zDiff[c.o]

  saveChoords()
end

function right()
  turtle.turnRight()

  c.o = c.o + 1

  if c.o > 4 then
    c.o = 1
  end

  saveChoords()
end

function left()
  turtle.turnLeft()

  c.o = c.o - 1

  if c.o < 1 then
    c.o = 4
  end

  saveChoords()
end

function up()
  while not turtle.up() do
    turtle.digUp()
  end

  c.y = c.y + 1

  saveChoords()
end

function checkBlock()
  f, block = turtle.inspect()

  if block ~= nil then
    mine = true

    for i = 1,#blacklist do
      if block.name == blacklist[i] then
        mine = false
      end
    end

    if mine then
      turtle.dig()
    end
  end
end

function digLayer()
  down()

  checkBlock()

  for i = 1,3 do
    right()
    checkBlock()
  end
end

function look(o)
  while c.o ~= o do
    right()
  end
end

function exitHole()
  while c.y < 65 do
    up()
  end

  for i = 1,16 do
    turtle.select(i)

    item = turtle.getItemDetail(i)

    if item ~= nil then
      drop = false

      for i = 1,#blacklist do
        if item.name == blacklist[i] then
          drop = true
        end
      end

      if drop then
        turtle.dropDown()
      end
    end
  end

  look(1)

  forward()
  forward()
  left()
  forward()

  c.pos = c.pos - 1

  if c.pos < 0 then
    look(2)

    for i = 1,c.maxPos+2 do
      forward()
    end

    left()

    for i = 1,c.maxPos/2+1 do
      forward()
    end

    c.pos = c.maxPos
  end

  saveChoords()
end

function hole()
  digging = true

  while digging do
    digLayer()
  end
end

hole()