utils

local timeout = 10
function forward()
  local t = 0
  while not turtle.forward() do
    turtle.dig()
    turtle.attack()
    t = t + 1
    if t == timeout then return false end
  end
  return true
end

local function up()
  local t = 0
  while not turtle.up() do
    turtle.digUp()
    turtle.attackUp()
     t = t + 1
     if t == timeout then return false end
  end
  return true
end

local function down()
  local t = 0
  while not turtle.down() do
    turtle.digDown()
    turtle.attackDown()
    t = t + 1
    if t == timeout then return false end
  end
  return true
end

local function timesX(func, n)
  if func ~= nil then
    for i = 1, n do
      if not func() then return false end
    end
  end
  return true
end


local function shouldMove(x, z, dx, dz)
  return (x * dx > 0) or (z * dz > 0)
end

function goto(x, y, z)
  while turtle.y > y do if not down() then return false end end
  while turtle.y < y do if not up() then return false end end
  local xx = x - turtle.x
  local zz = z - turtle.z
  local dx, dz = turtle.dir()
  local f = shouldMove(xx, zz, dx, dz)
  local b = shouldMove(xx, zz, -dx, -dz)
  local l = shouldMove(xx, zz, dz, -dx)
  local r = shouldMove(xx, zz, -dz, dx)
  if f and not timesX(forward, xx * dx + zz * dz) then return false end
  if l then turtle.turnLeft() if not timesX(forward, xx * dz - zz * dx) then return false end end
  if r then turtle.turnRight() if not timesX(forward, zz * dx - xx * dz) then return false end end
  if b then
    if l then turtle.turnLeft()
    else
      if not r then turtle.turnRight() end
      turtle.turnRight()
    end
    if not timesX(forward, xx * -dx + zz * -dz) then return false end
  end
  return x == turtle.x and y == turtle.y and z == turtle.z
end