local vecMods = { {0,-1}, { 1,0}, { 0,1}, {-1,0} }
local dir = 2
local out = 0
local currentLoc = {0,0}

function processField()
  print("Processed!")
end

function moveOn()
  currentLoc[1] = currentLoc[1] + vecMods[dir][1]
  currentLoc[2] = currentLoc[2] + vecMods[dir][2]
end

function isEdge(loc)
  local edgeLocs = {
                      { -out, -out },
                      { out, -out },
                      { -out, out },
                      { out, out }
                   }
  for _,v in pairs( edgeLocs ) do
    if v[1] == loc[1] and v[2] == loc[2] then return true end
  end
  return false
end

function moveOut()
  dir = 2
  moveOn()
  out = out + 1
end



processField()
while true do
  moveOut()
  startLoc = {}
  startLoc.x = currentLoc[1]
  startLoc.y = currentLoc[2]
  processField()
  dir = 3
  moveOn()
  processField()
  while (currentLoc[1] ~= startLoc.x or currentLoc[2] ~= startLoc.y) do
    if isEdge(currentLoc) then dir = dir % 4 + 1 end
    moveOn()
    processField()
  end
end