import hashlib, hmac
seed = bytes.fromhex("3c135dfb5c17bb6c3558fd0cfddf254c324b1a9b3c4c0bb3b367bd2cd45b4638")
assert hashlib.sha256(seed).hexdigest() == "202dc695ae5caab4f8e4fe65086cbe4491b428fdd7fe47a0d84683f8d6d7f28a"
ref = "DRW-001666"
# Eligible ticket numbers frozen after sales closed and payments were reconciled
ranges = [(1, 1200)]
setHash = hashlib.sha256("\n".join(f"{a}-{b}" for a, b in ranges).encode()).hexdigest()
assert setHash == "b84c6c89b39a1678c6a5a534ff4bca667b38ac53ea255bdd8dc9408c530a410b"
m = sum(b - a + 1 for a, b in ranges)
randomness = "e4921cb1bba122b05c78b17f15bfbaf9594a5d01d10a8daea4cc494603b9dc72"  # from the drand round link above
limit = ((1 << 48) // m) * m
used = set()
for rank in range(1, 1 + 1):   # selection 1, then alternates / further prizes
    c = 0
    while True:
        part = f"{rank}|" if rank > 1 else ""
        msg = f"GBC-5050-v3|{ref}|{m}|{setHash}|{randomness}|{part}{c}".encode()
        v = int.from_bytes(hmac.new(seed, msg, hashlib.sha256).digest()[:6], "big")
        c += 1
        if v >= limit or (v % m + 1) in used:
            continue
        k = v % m + 1
        used.add(k)
        break
    for a, b in ranges:
        if k <= b - a + 1:
            print("selection", rank, "ticket", a + k - 1)
            break
        k -= b - a + 1
# (a prize raffle with "one prize per person" also skips a buyer's other tickets — the server applies that rule from the frozen data)