#!/usr/bin/python

# Python just-dice.com verifier, based on the JavaScript verifiers described on the "Fair?" pages at just-dice.com
#
# example usage:
#   python just-dice.py ia_zEVRJ_VqfHPDbqGEYm39d6d2yg58_t1brUjO2LwiDBVydO7sKh6Sulw8123ec 7ab7df124145d0fcf931c142aabcca2022f60775d6afa692be114c09ff4408cf 515035004112265853362847 12
#   prints the last 10 lucky numbers, starting with roll 12 since the last randomize, which is this bet: https://just-dice.com/roll/23616559

import hashlib
import hmac
import sys

# parse command line arguments
if len(sys.argv) < 5:
    print("usage: python just-dice.py server-seed server-seed-hash client-seed last-roll [roll-count]")
    exit(-1)
print(sys.argv[1])
serverSeed = sys.argv[1]
serverSeedHash = sys.argv[2]
clientSeed = sys.argv[3]
lastNonce = int(sys.argv[4])
nonceCount = 10
if len(sys.argv) == 6:
    nonceCount = int(sys.argv[5])

# convert string to binary array
def str2bin(string):
    return bytes(string, 'latin-1')

# test server hash
hash_object = hashlib.sha256(str2bin(serverSeed))
hash = hash_object.hexdigest()
if hash == serverSeedHash:
    print('Server secret hash is correct.')
else:
    print('Server secret hash check failed!')

# calculate and show lucky numbers
for nonce in range(lastNonce, lastNonce - nonceCount, -1):
    hash_object = hmac.new(str2bin(serverSeed), str2bin(clientSeed + ":" + str(nonce)), hashlib.sha512)
    hash = hash_object.hexdigest()
    i = 0
    while True:
        if i == 25:
            l3 = hash[-3:]
            l3p = int(l3, 16)
            #print('last 3: ' + l3 + ' as int: ' + l3p)
            roll = l3p / 10000
            break
        else:
            f5 = hash[5 * i : 5 + 5 * i]
            f5p = int(f5, 16)
            #print(f5 + ' as int: ' + f5p);
            if f5p < 1000000:
                roll = f5p / 10000
                break
            i = i + 1
    lucky = ('0' + '{:.4f}'.format(roll))[-7:]
    print(str(nonce) + ": " + lucky)