Combine Telegram animated stickers (.tgs) in a single one

combine.py

import sys
import gzip
import json

from collections import defaultdict

if len(sys.argv) < 3:
    print("Wrong args. Usage: python combine.py file1.tgs file2.tgs ...")

files = map(lambda f: open(f, "rb"), sys.argv[1:])

stickers = [json.loads(gzip.decompress(file.read())) for file in files]

for file in files:
    file.close()

final = stickers[0]

id_counter = 0

ref_ids = defaultdict(lambda: [None, None])

for layer in final["layers"]:
    if ref_id := layer.get("refId"):
        ref_ids[ref_id][0] = layer

for asset in final["assets"]:
    ref_ids[asset["id"]][1] = asset

for sticker in stickers[1:]:
    for layer in sticker["layers"]:
        if ref_id := layer.get("refId"):
            ref_ids[ref_id][0] = layer

    for asset in sticker["assets"]:
        ref_ids[asset["id"]][1] = asset

    final["assets"].extend(sticker["assets"])
    final["layers"].extend(sticker["layers"])

for layer, asset in ref_ids.values():
    if layer and asset and (ref_id := layer.get("refId")):
        layer["refId"] = asset["id"] = f"id{id_counter}"
        id_counter += 1

with open("output.tgs", "wb") as output_tgs, open("output.json", "w+") as output_json:
    json.dump(final, output_json, indent=4)
    jsoned = json.dumps(final, separators=(',', ':'))
    output_tgs.write(gzip.compress(jsoned.encode()))