plantuml server url decoder encoder

plantuml_server_url_decode.py

# https://plantuml.com/text-encoding
# https://github.com/dougn/python-plantuml/blob/master/plantuml.py#L64

import zlib
import base64

maketrans = bytes.maketrans

plantuml_alphabet = string.digits + string.ascii_uppercase + string.ascii_lowercase + '-_'
base64_alphabet   = string.ascii_uppercase + string.ascii_lowercase + string.digits + '+/'
b64_to_plantuml = maketrans(base64_alphabet.encode('utf-8'), plantuml_alphabet.encode('utf-8'))
plantuml_to_b64 = maketrans(plantuml_alphabet.encode('utf-8'), base64_alphabet.encode('utf-8'))

def plantuml_encode(plantuml_text):
    """zlib compress the plantuml text and encode it for the plantuml server"""
    zlibbed_str = zlib.compress(plantuml_text.encode('utf-8'))
    compressed_string = zlibbed_str[2:-4]
    return base64.b64encode(compressed_string).translate(b64_to_plantuml).decode('utf-8')

def plantuml_decode(plantuml_url):
    """decode plantuml encoded url back to plantuml text"""
    data = base64.b64decode(plantuml_url.translate(plantuml_to_b64).encode("utf-8"))
    dec = zlib.decompressobj() # without check the crc.
    header = b'x\x9c'
    return dec.decompress(header + data).decode("utf-8")


url = "SyfFKj2rKt3CoKnELR1Io4ZDoSa70000"

print(plantuml_decode(url))
print(plantuml_encode(plantuml_decode(url)))