Bitcoin Forum

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from __future__ import print_function

import json
import requests
import sys

from hashlib import sha256

def make_draw(amounts, hash):
    hash_num = int(hash, 16)
    total = sum(amounts)
    total_bits = len(bin(total)) - 2
    rand_num = int(bin(hash_num)[-total_bits:], 2)
    offset = 0
    while rand_num > total:
        offset += 1
        rand_num ^= int(bin(hash_num)[-total_bits-offset:-offset], 2)

    i = lottery(amounts, rand_num)
    return i

def lottery(elements, rand):
    value = 0
    for i,el in enumerate(elements):
        value += el
        if rand <= value:
            return i

def prettify(dictionary):
    return json.dumps(dictionary, indent=4, sort_keys=True)

URL = 'http://nolimits-lottery.com/api/draw/' + sys.argv[1]

draw = requests.get(URL).json()

#print "DRAW: ", prettify(draw)

participations = sorted(draw['participations'], key=lambda p:p['amount'], reverse=True)
amounts = map(lambda p:p['amount'], participations)
combined_hash = sha256(reduce(lambda acc, p: acc + p['txid'], participations, draw['seed'])).hexdigest()

total = sum(amounts)
reward = total/2
fee = total * 0.03125
i=0
results = []
while reward >= fee:
    if not participations:
        if results: results[-1]['amount']+=total-fee
        break
    winner = make_draw(amounts, combined_hash)
    result = dict(
        participation_id=participations[winner]['id'],
        place=i+1,
        amount=reward
    )
    results.append(result)
    winning_participation = participations.pop(winner)
    amounts = map(lambda p:p['amount'], participations)
    total = reward
    reward = total/2
    combined_hash = sha256(combined_hash + winning_participation['txid']).hexdigest()
    i+=1

#print "RESULTS: ", prettify(results)

real_winners = sorted(draw['winners'], key=lambda p:p['place'], reverse=True)
expected_winners = sorted(results, key=lambda p:p['place'], reverse=True)

for i, winner in enumerate(real_winners):
    if not expected_winners[i]['participation_id'] == winner['participation_id']:
        print("VERIFICATION FAILED")
        exit(1)

print("RESULT VERIFIED")