import copy
import json
import re
import sys


def mirror(wall, axis):
  # Wall points appear in the form 'PoolVector2Array( x1, y1, x2, y2, ..., x99, y99)'
  # Capture each float, noting that whole numbers won't have a decimal.
  matches =  re.findall(r" (\d+(?:\.\d+)?)", wall["points"])
  assert (len(matches) % 2) == 0

  # We have a flattened list of points. Even indices are x values. Mirror them
  # across the y-axis, but leave the y values alone.
  mirrored_points = (f"{2*axis*256-float(n)}" if i % 2 == 0 else n for i, n in enumerate(matches))

  new_wall = copy.deepcopy(wall)
  new_wall["points"] = f"PoolVector2Array( {', '.join(mirrored_points)} )"

  return new_wall


def main():
  if len(sys.argv) != 2:
    print(f"Usage: {sys.argv[0]} map_file", file=sys.stderr)
    sys.exit(1)

  map_file = sys.argv[1]
  with open(map_file, "r") as f:
    d = json.load(f)

  world = d["world"]

  # This assumes the first wall on the first level is the target.
  walls = world["levels"]["0"]["walls"]
  # Mirroring is along the y-axis, even width assumed.
  axis = round(world["width"] / 2)
  new_wall = mirror(walls[0], axis)

  # The next node id is stored as a hex string. Use and update manually for the new wall.
  next_node_id = world["next_node_id"]
  new_wall["node_id"] = next_node_id
  world["next_node_id"] = format(int(next_node_id, 16)+1, "x")
  world["levels"]["0"]["walls"].append(new_wall)

  with open(f"mirrored_{map_file}", "w") as f:
    json.dump(d, f)


if __name__ == "__main__":
  main()