TurtleScanner

local width, height = term.getSize();
local width_half = width/2;
local room = {};
  --0=untraversed
  --1=air
  --2=block
  --5=air-traveled
  --6=block traveled
local tPos = {1,1};
local moves = {
  {1,0},
  {0,1},
  {-1,0},
  {0,-1}
}; moves[0] = moves[4];
local orientation = 0;
        --right = 0
        --down = 1
        --left = 2
        --up = 3
local closedSet = {};
local openSet = {};
local node = 0;


--Create the Room
for x=-2,2 do
  room[x]={};
  for z=-2,2 do
    room[x][z]=0;
  end
end
room[1][1] = 1;

function turnLeft()
  turtle.turnLeft();
  orientation = (orientation - 1) % 4;
end

function turnRight()
  turtle.turnRight();
  orientation = (orientation + 1) % 4;
end

function setOrientation(o)
  o = o % 4;
  if(orientation==o)then return; end
  local x;
  if( (orientation-1) % 4 == o)then
    x = turnLeft;
  else
    x = turnRight;
  end
  while(orientation~=o)do
    x();
  end
  if(orientation~=o)then print("ERRRRRRORR"); end
end

function isInRoom(o1)
  o1 = o1 or orientation;
  if(o1==0)then o1=4; end
  local newX, newY = tPos[1]+moves[o1][1], tPos[2]+moves[o1][2];
  if(room[newX]==nil)then room[newX]={}; end
  if(room[newX][newY]==5 or room[newX][newY]==2)then return false, newX, newY; end
  return true, newX, newY;
end

function getPossibleOptions()
  local optOrientations = {};
  local isIn, newX, newY;
  local isNot = (node~=0 and (node[1]+2)%4) or 5;
  for i = 0, 3 do
    isIn, newX, newY = isInRoom(i);
    if(isIn)then
      setOrientation(i);
      if(not turtle.detect())then
        if(i~=isNot)then
          table.insert(optOrientations, i);
          --room[newX][newY] = 1;
          if(room[newX][newY]~=5)then
            if(go())then
              move();
            end
          end
        end
      else
        room[newX][newY] = 2;
      end
    end
  end
  return optOrientations;
end

function moveRight()
  setOrientation(0);
end

function moveUp()
  setOrientation(3);
end

function moveDown()
  setOrientation(1);
end

function moveLeft()
  setOrientation(2);
end

function goBack()
  if(node == 0)then return false; end
  setOrientation((node[1]+2)%4);
  local x2 = (orientation==0 and 4) or orientation;
  local resp = turtle.forward();
  if(resp)then
    tPos[1] = tPos[1]+moves[x2][1];
    tPos[2] = tPos[2]+moves[x2][2];
    node = node[2];
    redraw();
  end
  return true;
end

function go(x1)
  if(x1)then x1(); end
  local x2 = (orientation==0 and 4) or orientation;
  local resp = turtle.forward();
  if(resp)then
    tPos[1] = tPos[1]+moves[x2][1];
    tPos[2] = tPos[2]+moves[x2][2];
    node = {orientation,node};
    room[tPos[1]][tPos[2]] = 5;
    redraw();
  end
  return resp;
end

function redraw()
  term.clear();
  local i1 = 1;
  local half = width_half;
  local half2 = height/2;
  local tX, tY = tPos[1], tPos[2];
  for i = tX-5,tX+5 do
    local y1 = 1;
    if(room[i]==nil)then room[i] = {}; end
    for y = tY-5,tY+5 do
      term.setCursorPos(tX-i+half,tY-y+half2);
      if(room[i][y] == 2)then
        term.write("x");
      elseif(room[i][y] == 1 or room[i][y] == 5)then
        term.write("_");
      else
        term.write("?");
      end
      y1 = y1+1;
    end
    i1 = i1+1;
  end
  term.setCursorPos(half,half2);
  term.write("o");
end

function move()
  local posOrients = getPossibleOptions();
  room[tPos[1]][tPos[2]] = 5;
  goBack();
end

move();
term.setCursorPos(1,1);