local w,h,d,oy= ...
-- n -> 0, w -> 1, s -> 2, e -> 3
local dir = 0
local x,y,z = 0, 0, 0

local function oppositeDir(d)
  if d == 0 then return 2
  elseif d == 1 then return 3
  elseif d == 2 then return 0
  elseif d == 3 then return 1
  else return d end
end

local function tryDig()
  while turtle.detect() do
    if not turtle.dig() then return false end
  end

  return true
end

local function tryDigDown()
  while turtle.detectDown() do
    if not turtle.digDown() then return false end
  end

  return true
end

local function tryDigUp()
  while turtle.detectUp() do
    if not turtle.digUp() then return false end
  end

  return true
end

local function refuel()
  local fuelLevel = turtle.getFuelLevel()
  if fuelLevel == "unlimited" or fuelLevel > 0 then
    return
  end

  local function tryRefuel()
    for n=1,16 do
      if turtle.getItemCount(n) > 0 then
        turtle.select(n)
        if turtle.refuel(n) then
          turtle.select(n)
          return true
        end
      end
    end
    turtle.select(1)
    return false
  end

  if not tryRefuel() then
    print("Out of fuel. Please add more fuel!")
    while not tryRefuel() do
      os.pullEvent("turtle_inventory")
    end
    print("Resuming...")
  end
end

local function move()
  refuel()

  while not turtle.forward() do
    if turtle.detect() then
      if not tryDig() then return false end
    elseif turtle.attack() then
      print("Something in the way. Attacking...")
    else sleep(0.5) end
  end

  if dir == 0 then z = z + 1
  elseif dir == 1 then x = x - 1
  elseif dir == 2 then z = z - 1
  elseif dir == 3 then x = x + 1
  else return false end

  return true
end

local function moveUp()
  refuel()

  while not turtle.up() do
    if turtle.detectUp() then
      if not tryDigUp() then return false end
    elseif turtle.attackUp() then
      print("Something in the way. Attacking...")
    else sleep(0.5) end
  end

  y = y + 1

  return true

end

local function moveDown()
  refuel()

  while not turtle.down() do
    if turtle.detectDown() then
      if not tryDigDown() then return false end
    elseif turtle.attackDown() then
      print("Something in the way. Attacking...")
    else sleep(0.5) end
  end

  y = y - 1

  return true
end

local function turn(d)

  if dir == d then return end

  local dx = dir - d

  while dx ~= 0 do
    if dx < 0 then
      if dx == -3 then
        turtle.turnRight()
        dx = 0
      else
        turtle.turnLeft()
        dx = dx + 1
      end
    else
      if dx == 3 then
        turtle.turnLeft()
        dx = 0
      else
        turtle.turnRight()
        dx = dx - 1
      end
    end
  end

  dir = d

end

local function navigateTo(ax, ay, az)
  while y ~= ay do
    if y > ay then
      moveDown()
    else
      moveUp()
    end
  end

  while x ~= ax do
    if x > ax then
      turn(1)
      move()
    else
      turn(3)
      move()
    end
  end

  while z ~= az do
    if z > az then
      turn(2)
      move()
    else
      turn(0)
      move()
    end
  end
end

local function emptyInv()
  local lx, ly, lz, ld = x, y, z, dir

  local hw = math.floor(w/2)

  print("x: %d, y:%d, z:%d", x, y, z)

  navigateTo(hw, 0, -1)

  for n=2,16 do
    turtle.select(n)
    turtle.dropDown()
  end

  turtle.select(1)

  turn(0)
  move()

  navigateTo(lx, ly, lz)

  turn(ld)
end

local function invHasSpace()
  return turtle.getItemCount(16) == 0
end



if w == nil or h == nil or d == nil then
  print("Usage: quarry <width> <height> <depth>")
  return
end

if oy == nil then oy = 0 end

w = tonumber(w)
h = tonumber(h)
d = tonumber(d)
oy = tonumber(oy)

assert(w ~= nil, "Width must be a number")
assert(h ~= nil, "Height must be a number")
assert(d ~= nil, "Depth must be a number")
assert(oy ~= nil, "Y-offset must be a number")

if w <= 0 or h <= 0 or d <= 0 then
  print("All dimension values must be positive!")
  return
end

w = math.floor(w)
h = math.floor(h)
d = math.floor(d)
oy = math.floor(oy)

print(string.format("Starting to mine in %dx%dx%d area. With Y-offset: %d", w, h, d, oy))

local hw = math.floor(w/2)

turn(1)

while hw > 0 do
  tryDig()
  turtle.forward()
  hw = hw - 1
end

turn(0)

local n = true
local wdir = 1
local hdir = 1

local wi,hi,di = 0, 1, 0

local wk = w
local hk = h

while di ~= d do

  while wi ~= wk do

    while hi ~= hk do

      if not invHasSpace() then
        emptyInv()
      end

      tryDig()
      move()

      hi = hi + hdir

    end

    if math.fmod(wi + wdir, w) ~= 0 then
      if n then
        turn(3)
      else
        turn(1)
      end
      tryDig()
      move()
    end

    if hk == h then
      hk = 1
      turn(2)
    else
      hk = h
      turn(0)
    end

    hdir = -hdir

    wi = wi + wdir
  end

  if wk == w then
    wk = 0
  else
    wk = w
  end
  wdir = -wdir

  di = di + 1
  n = not n

  if di ~= d then
    tryDigDown()
    moveDown()
  end
end

print("Task finished!")