ambidex.py

import zlib
import base64
import json
import sys


def flip_entity(entity):

    # translation tables
    newX = [-3,-2, 0, 2,3,2,0,-2]
    newY = [ 0,-2,-3,-2,0,2,3, 2]
    flipDirC = [1,0,7,6,5,4,3,2]
    flipDirR = [0,7,2,5,4,3,6,1]
    flipDirS = [0,7,6,5,4,3,2,1]
    
    entity['position']['x'] = -entity['position']['x']
    if "-rail" in entity['name']:
        # Entity is either a straight or a curved rail
        table = flipDirR if 'straight' in entity['name'] else flipDirC
        entity['direction'] = table[entity.get('direction', 0)]
    else:
        # Entity is a signal
        table = flipDirS
        entity['direction'] = table[entity.get('direction', 0)]
        entity['position']['x'], entity['position']['y'] = \
            entity['position']['x'] + newX[entity['direction']], \
            entity['position']['y'] + newY[entity['direction']]

with open(sys.argv[1]) as f:
	s = f.read()

# decode
data = json.loads(str(zlib.decompress(base64.b64decode(s[1:]), wbits=0), 'utf-8'))

# process
entities = data['blueprint']['entities']
for entity in entities:
	flip_entity(entity)

# encode
outdata = "0" + str(base64.b64encode(zlib.compress(json.dumps(bp_json_obj,separators=(',', ':')).encode('utf-8'),9)),'utf-8')

with open(sys.argv[2],'w') as file:
	file.write(bpsO)