Historically Accurate Tree Restoration [Factorio]

/c
--[[ HISTORICALLY ACCURATE TREE RESTORATION ]]
local TREES = {"tree-01","tree-02","tree-02-red","tree-03","tree-04","tree-05","tree-06","tree-06-brown","tree-07","tree-08","tree-08-brown","tree-08-red","tree-09","tree-09-brown","tree-09-red"}
local function bounding_box_from_gps_tags(s)
  local x1 = math.huge
  local y1,x2,y2 = x1,-x1,-x1
  for x,y in s:gmatch("%[gps=([+-]?%d+),([+-]?%d+)%]") do
    x1 = math.min(x1, x+0)
    y1 = math.min(y1, y+0)
    x2 = math.max(x2, x+0)
    y2 = math.max(y2, y+0)
  end
  return { left_top = {x=x1,y=y1}, right_bottom = {x=x2,y=y2} }
end
local function chunks_at_least_partly_inside(surface, bb)
  local result = {}
  for c in surface.get_chunks() do
    if c.area.left_top.x <= bb.right_bottom.x and
       c.area.left_top.y <= bb.right_bottom.y and
       c.area.right_bottom.x >= bb.left_top.x and
       c.area.right_bottom.y >= bb.left_top.y
    then
      result[#result+1] = c
    end
  end
  return result
end
local function go(s)
  local surface = game.player.surface
  local chunks = chunks_at_least_partly_inside(surface, bounding_box_from_gps_tags(s))
  if #chunks > 0 then
    surface.regenerate_entity(TREES, chunks)
    game.print("Restored default trees to " .. #chunks .. " chunks.")
  end
end
go ""