miner

local tArgs = { ... }
if #tArgs ~= 1 then
  print("Startentfernung benoetigt.")
  return
end

local nz = -tonumber(tArgs[1])

local left = 1
local x, y, z = 0, 0, 0
local xd, zd = 0, -1
local nx = 0
local err = false

function mineat()
  goto(nx, 0, nz, 0, -1)
  while true do
    if not trydown() then
      home()
      break
    end
  end
end

function collect()
  for n = 1, 16 do
    local cnt = turtle.getItemCount(n)
    if cnt == 0 then
      return true
    end
  end
  return false
end

function trydown()
  while not turtle.down() do
    if turtle.detectDown() then
      if turtle.digDown() then
        if not collect() then
          return false
        end
      else
        err = true
        return false
      end
    end
  end
  y = y - 1
  return true
end

function unload()
  for n = 1, 16 do
    local cnt = turtle.getItemCount(n)
    if cnt > 0 then
      turtle.select(n)
      turtle.drop()
    end
  end
  turtle.select(1)
end

function home()
  goto(0, 0, 0, 0, 1)
  unload()
  turn(0, -1)
  if err then
    err = false
    nz = nz - 1
    print("Now at "..(-nz).." distance...")
  else
    mineat()
  end
end

function turn(txd, tzd)
  while xd ~= txd or zd ~= tzd do
    turtle.turnRight()
    local tmp = xd
    xd = -zd
    zd = tmp
  end
end

function goto(tx, ty, tz, txd, tzd)
  while ty > y do
    turtle.up()
    y = y + 1
  end
  while ty < y do
    turtle.down()
    y = y - 1
  end
  while tz < z do
    turn(0, -1)
    turtle.forward()
    z = z - 1
  end
  while tz > z do
    turn(0, 1)
    turtle.forward()
    z = z + 1
  end
  while tx < x do
    turn(-1, 0)
    turtle.forward()
    x = x - 1
  end
  while tx > x do
    turn(1, 0)
    turtle.forward()
    x = x + 1
  end
  turn(txd, tzd)
end

mineat()