--------------------------------------------------------------------------------------------------------------------
--> GLOBALS
--------------------------------------------------------------------------------------------------------------------

-- Position we reside in, relative to time of execution
local pos = vector.new(0, 0, 0);

-- Direction we're facing
DIRECTION_FORWARD = 0x0;
DIRECTION_LEFT    = 0x1;
DIRECTION_BACK    = 0x2;
DIRECTION_RIGHT   = 0x3;
local dir = DIRECTION_FORWARD;

--------------------------------------------------------------------------------------------------------------------
--> TURTLE ABSTRACTION FUNCTIONS
--------------------------------------------------------------------------------------------------------------------

---
--- Rotates in dir, x times.  x will default to one.
--- This updates the orientation of the turtle.
---
local function rotate(d, x)
  if (not x) then
    x = 1;
  end

  for i = 1, x do
    if (d == DIRECTION_LEFT) then
      turtle.turnLeft();

      -- Increase with clamp
      if (dir == 3) then
        dir = 0;
      else
        dir = dir + 1;
      end
    else
      turtle.turnRight();

      -- Decrease with clamp
      if (dir == 0) then
        dir = 3;
      else
        dir = dir - 1;
      end
    end
  end
end

-- Helper functions for above
local function left(x) rotate(DIRECTION_LEFT, x); end
local function right(x) rotate(DIRECTION_RIGHT, x); end

---
--- Changes the angle of a turtle to match desired using
--- as little rotations possible
---
local function setAngle(desired)
  local min = math.min(dir, desired);
  local max = math.max(dir, desired);
  local diff = max - min;

  -- 180 spins / right - forward
  if (diff == 2) then
    return left(2);
  elseif (diff == 3) then
    return right();
  end

  -- Should always be one right/left change
  if (desired > dir) then
    left();
  elseif (desired < dir) then
    right();
  end
end

---
--- Moves x blocks fowards caving one block above the turtle
--- and one infront of it.  Updates coords.
---
local function move(x)
  for i = 1, x do

    -- Forward can fail, dig until we move
    -- forwards succesfully
    repeat
      turtle.dig();
      turtle.digUp();
    until turtle.forward();

    -- Update coords
    if (dir == DIRECTION_FORWARD) then
      pos.y = pos.y + 1;
    elseif (dir == DIRECTION_LEFT) then
      pos.x = pos.x - 1;
    elseif (dir == DIRECTION_BACK) then
      pos.y = pos.y - 1;
    elseif (dir == DIRECTION_RIGHT) then
      pos.x = pos.x + 1;
    end

  end
end

---
--- Goes to a vector.
---
local function goto(x, y, preserve)
  if (pos.x ~= x) then
    if (pos.x > x) then
      setAngle(DIRECTION_LEFT);
    else
      setAngle(DIRECTION_RIGHT);
    end

    move(math.abs(pos.x - x));
  end

  if (pos.y ~= y) then
    if (pos.y > y) then
      setAngle(DIRECTION_BACK);
    else
      setAngle(DIRECTION_FORWARD);
    end

    move(math.abs(pos.y - y));
  end
end

---
--- Returns the turtle so that it's facing the block that it started on
---
local function goHome()
  goto(0, 0, true);
end

--[[
---
--
---
local function dump()

  -- Cache selected index
  local selected = ttl("getSelectedSlot");

  -- Dump items
  for i = 1, 16 do
    if (ttl("select", i)) then
      local count = ttl("getItemCount");

      if (count > 0) then
        ttl("drop", count - 1);
      end
    end
  end

  -- Restore selected index
  ttl("select", selected);
end

---
--- Refuel from chest infront of the turtle
---
function refuel()

  local limit = ttl("getFuelLimit");
  local current = ttl("getFuelLevel");
  local need = limit - current;
  local count = math.ceil(need / 1000);
  local selected = ttl("getSelectedSlot");

  if (count > 64) then
   count = 64;
  end

  -- Attempt to aqquire fuel
  if (not ttl("suck", count)) then
    error("Could not refuel from storage");
  end

  -- Find fuel and refuel from it
  for i = 1, 16 do
    if (ttl("select", i)) then
      local count = ttl("getItemCount");
      if (ttl("refuel", count - 1)) then
        break;
      end
    end
  end

  ttl("select", selected);
end]]--

local arg = { ... };
local x = tonumber(arg[ 1 ]);
local y = tonumber(arg[ 2 ]);
goto(x, y);