dig.lua

local robot = component.proxy(component.list("robot"))
local sides = require("sides")

local size = 16

local r = component.robot
--local x, y, z, f = 0, 0, 0, 0
local x, y, z, f = 0
local dropping = false
local delta = {[0] = function() x = x + 1 end, [1] = function() y = y + 1 end,
               [2] = function() x = x - 1 end, [3] = function() y = y - 1 end}

local function turnRight()
  robot.turnRight()
  f = (f + 1) % 4
end

local function turnLeft()
  robot.turnLeft()
  f = (f - 1) % 4
end

local function turnTowards(side)
  if f == side - 1 then
    turnRight()
  else
    while f ~= side do
      turnLeft()
    end
  end
end

local checkedDrop

local function clearBlock(side, cannotRetry)
  while r.suck(side) do
    checkedDrop()
  end
  local result, reason = r.swing(side)
  if result then
    checkedDrop()
  else
    local _, what = r.detect(side)
    if cannotRetry and what ~= "air" and what ~= "entity" then
      return false
    end
  end
  return true
end

local function tryMove(side)
  side = side or sides.forward
  local tries = 10
  while not r.move(side) do
    tries = tries - 1
    if not clearBlock(side, tries < 1) then
      return false
    end
  end
  if side == sides.down then
    z = z + 1
  elseif side == sides.up then
    z = z - 1
  else
    delta[f]()
  end
  return true
end

local function moveTo(tx, ty, tz, backwards)
  local axes = {
    function()
      while z > tz do
        tryMove(sides.up)
      end
      while z < tz do
        tryMove(sides.down)
      end
    end,
    function()
      if y > ty then
        turnTowards(3)
        repeat tryMove() until y == ty
      elseif y < ty then
        turnTowards(1)
        repeat tryMove() until y == ty
      end
    end,
    function()
      if x > tx then
        turnTowards(2)
        repeat tryMove() until x == tx
      elseif x < tx then
        turnTowards(0)
        repeat tryMove() until x == tx
      end
    end
  }
  if backwards then
    for axis = 3, 1, -1 do
      axes[axis]()
    end
  else
    for axis = 1, 3 do
      axes[axis]()
    end
  end
end

function checkedDrop(force)
  local empty = 0
  for slot = 1, 16 do
    if robot.count(slot) == 0 then
      empty = empty + 1
    end
  end
  if not dropping and empty == 0 or force and empty < 16 then
    local ox, oy, oz, of = x, y, z, f
    dropping = true
    moveTo(0, 0, 0)
    turnTowards(2)

    for slot = 1, 16 do
      if robot.count(slot) > 0 then
        robot.select(slot)
        local wait = 1
        repeat
          if not robot.drop() then
            os.sleep(wait)
            wait = math.min(10, wait + 1)
          end
        until robot.count(slot) == 0
      end
    end
    robot.select(1)

    dropping = false
    moveTo(ox, oy, oz, true)
    turnTowards(of)
  end
end

local function step()
  clearBlock(sides.down)
  if not tryMove() then
    return false
  end
  clearBlock(sides.up)
  return true
end

local function turn(i)
  if i % 2 == 1 then
    turnRight()
  else
    turnLeft()
  end
end

local function digLayer()
  for i = 1, size do
    for j = 1, size - 1 do
      if not step() then
        return false
      end
    end
    if i < size then
      turn(i)
      if not step() then
        return false
      end
      turn(i)
    else
      turnRight()
      if size % 2 == 1 then
        turnRight()
      end
      for i = 1, 3 do
        if not tryMove(sides.down) then
          return false
        end
      end
    end
  end
  return true
end

repeat until not digLayer()
moveTo(0, 0, 0)
turnTowards(0)
checkedDrop(true)

computer.shutdown()