generate_normandy_id.py

from hashlib import sha256
from json import dumps
from math import floor
from uuid import uuid4


def evalute(input, bucket_start, bucket_width, n_buckets):
    value = sha256(dumps(input).replace(" ", "").encode("utf-8")).hexdigest()[:12]
    wrapped_start = bucket_start % n_buckets
    end = wrapped_start + bucket_width

    if end > n_buckets:
        return (
            in_bucket(value, 0, end % n_buckets, n_buckets) or
            in_bucket(value, wrapped_start, n_buckets, n_buckets)
        )

    return in_bucket(value, wrapped_start, end, n_buckets)


def in_bucket(value, bucket_start, bucket_end, n_buckets):
    min_hash = fraction_to_key(bucket_start / n_buckets)
    max_hash = fraction_to_key(bucket_end / n_buckets)
    return min_hash <= value < max_hash

def fraction_to_key(f):
    assert 0 <= f <= 1
    return '%012x' % int(f * ((2 ** 48) - 1))


found = False
while not found:
    uuid = str(uuid4())
    found = evalute(["global-v1", uuid], 9645, 200, 10000)

print(uuid)