import hashlib, binascii, struct, array, os, time, sys, optparse
import scrypt

from construct import *


def main():
  options = get_args()

  algorithm = get_algorithm(options)

  input_script  = create_input_script(options.timestamp)
  output_script = create_output_script(options.pubkey)
  # hash merkle root is the double sha256 hash of the transaction(s) 
  tx = create_transaction(input_script, output_script,options)
  hash_merkle_root = hashlib.sha256(hashlib.sha256(tx).digest()).digest()
  print_block_info(options, hash_merkle_root)

  block_header        = create_block_header(hash_merkle_root, options.time, options.bits, options.nonce)
  genesis_hash, nonce = generate_hash(block_header, algorithm, options.nonce, options.bits)
  announce_found_genesis(genesis_hash, nonce)


def get_args():
  parser = optparse.OptionParser()
  parser.add_option("-t", "--time", dest="time", default=int(time.time()), 
                   type="int", help="the (unix) time when the genesisblock is created")
  parser.add_option("-z", "--timestamp", dest="timestamp", default="The Times 03/Jan/2009 Chancellor on brink of second bailout for banks",
                   type="string", help="the pszTimestamp found in the coinbase of the genesisblock")
  parser.add_option("-n", "--nonce", dest="nonce", default=0,
                   type="int", help="the first value of the nonce that will be incremented when searching the genesis hash")
  parser.add_option("-a", "--algorithm", dest="algorithm", default="SHA256",
                    help="the PoW algorithm: [SHA256|scrypt|X11|X13|X15]")
  parser.add_option("-p", "--pubkey", dest="pubkey", default="04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f",
                   type="string", help="the pubkey found in the output script")
  parser.add_option("-v", "--value", dest="value", default=5000000000,
                   type="int", help="the value in coins for the output, full value (exp. in bitcoin 5000000000 - To get other coins value: Block Value * 100000000)")
  parser.add_option("-b", "--bits", dest="bits",
                   type="int", help="the target in compact representation, associated to a difficulty of 1")

  (options, args) = parser.parse_args()
  if not options.bits:
    if options.algorithm == "scrypt" or options.algorithm == "X11" or options.algorithm == "X13" or options.algorithm == "X15":
      options.bits = 0x1e0ffff0
    else:
      options.bits = 0x1d00ffff
  return options

def get_algorithm(options):
  supported_algorithms = ["SHA256", "scrypt", "X11", "X13", "X15"]
  if options.algorithm in supported_algorithms:
    return options.algorithm
  else:
    sys.exit("Error: Given algorithm must be one of: " + str(supported_algorithms))

def create_input_script(psz_timestamp):
  psz_prefix = ""
  #use OP_PUSHDATA1 if required
  if len(psz_timestamp) > 76: psz_prefix = '4c'

  script_prefix = '04ffff001d0104' + psz_prefix + chr(len(psz_timestamp)).encode('hex')
  print (script_prefix + psz_timestamp.encode('hex'))
  return (script_prefix + psz_timestamp.encode('hex')).decode('hex')


def create_output_script(pubkey):
  script_len = '41'
  OP_CHECKSIG = 'ac'
  return (script_len + pubkey + OP_CHECKSIG).decode('hex')


def create_transaction(input_script, output_script,options):
  transaction = Struct("transaction",
    Bytes("version", 4),
    Byte("num_inputs"),
    StaticField("prev_output", 32),
    UBInt32('prev_out_idx'),
    Byte('input_script_len'),
    Bytes('input_script', len(input_script)),
    UBInt32('sequence'),
    Byte('num_outputs'),
    Bytes('out_value', 8),
    Byte('output_script_len'),
    Bytes('output_script',  0x43),
    UBInt32('locktime'))

  tx = transaction.parse('\x00'*(127 + len(input_script)))
  tx.version           = struct.pack('<I', 1)
  tx.num_inputs        = 1
  tx.prev_output       = struct.pack('<qqqq', 0,0,0,0)
  tx.prev_out_idx      = 0xFFFFFFFF
  tx.input_script_len  = len(input_script)
  tx.input_script      = input_script
  tx.sequence          = 0xFFFFFFFF
  tx.num_outputs       = 1
  tx.out_value         = struct.pack('<q' ,options.value)#0x000005f5e100)#012a05f200) #50 coins
  #tx.out_value         = struct.pack('<q' ,0x000000012a05f200) #50 coins
  tx.output_script_len = 0x43
  tx.output_script     = output_script
  tx.locktime          = 0 
  return transaction.build(tx)


def create_block_header(hash_merkle_root, time, bits, nonce):
  block_header = Struct("block_header",
    Bytes("version",4),
    Bytes("hash_prev_block", 32),
    Bytes("hash_merkle_root", 32),
    Bytes("time", 4),
    Bytes("bits", 4),
    Bytes("nonce", 4))

  genesisblock = block_header.parse('\x00'*80)
  genesisblock.version          = struct.pack('<I', 1)
  genesisblock.hash_prev_block  = struct.pack('<qqqq', 0,0,0,0)
  genesisblock.hash_merkle_root = hash_merkle_root
  genesisblock.time             = struct.pack('<I', time)
  genesisblock.bits             = struct.pack('<I', bits)
  genesisblock.nonce            = struct.pack('<I', nonce)
  return block_header.build(genesisblock)


# https://en.bitcoin.it/wiki/Block_hashing_algorithm
def generate_hash(data_block, algorithm, start_nonce, bits):
  print 'Searching for genesis hash..'
  nonce           = start_nonce
  last_updated    = time.time()
  # https://en.bitcoin.it/wiki/Difficulty
  target = (bits & 0xffffff) * 2**(8*((bits >> 24) - 3))

  while True:
    sha256_hash, header_hash = generate_hashes_from_block(data_block, algorithm)
    last_updated             = calculate_hashrate(nonce, last_updated)
    if is_genesis_hash(header_hash, target):
      if algorithm == "X11" or algorithm == "X13" or algorithm == "X15":
        return (header_hash, nonce)
      return (sha256_hash, nonce)
    else:
     nonce      = nonce + 1
     data_block = data_block[0:len(data_block) - 4] + struct.pack('<I', nonce)  


def generate_hashes_from_block(data_block, algorithm):
  sha256_hash = hashlib.sha256(hashlib.sha256(data_block).digest()).digest()[::-1]
  header_hash = ""
  if algorithm == 'scrypt':
    header_hash = scrypt.hash(data_block,data_block,1024,1,1,32)[::-1] 
  elif algorithm == 'SHA256':
    header_hash = sha256_hash
  elif algorithm == 'X11':
    try:
      exec('import %s' % "xcoin_hash")
    except ImportError:
      sys.exit("Cannot run X11 algorithm: module xcoin_hash not found")
    header_hash = xcoin_hash.getPoWHash(data_block)[::-1]
  elif algorithm == 'X13':
    try:
      exec('import %s' % "x13_hash")
    except ImportError:
      sys.exit("Cannot run X13 algorithm: module x13_hash not found")
    header_hash = x13_hash.getPoWHash(data_block)[::-1]
  elif algorithm == 'X15':
    try:
      exec('import %s' % "x15_hash")
    except ImportError:
      sys.exit("Cannot run X15 algorithm: module x15_hash not found")
    header_hash = x15_hash.getPoWHash(data_block)[::-1]
  return sha256_hash, header_hash


def is_genesis_hash(header_hash, target):
  return int(header_hash.encode('hex_codec'), 16) < target


def calculate_hashrate(nonce, last_updated):
  if nonce % 1000000 == 999999:
    now             = time.time()
    hashrate        = round(1000000/(now - last_updated))
    generation_time = round(pow(2, 32) / hashrate / 3600, 1)
    sys.stdout.write("\r%s hash/s, estimate: %s h"%(str(hashrate), str(generation_time)))
    sys.stdout.flush()
    return now
  else:
    return last_updated


def print_block_info(options, hash_merkle_root):
  print "algorithm: "    + (options.algorithm)
  print "merkle hash: "  + hash_merkle_root[::-1].encode('hex_codec')
  print "pszTimestamp: " + options.timestamp
  print "pubkey: "       + options.pubkey
  print "time: "         + str(options.time)
  print "bits: "         + str(hex(options.bits))


def announce_found_genesis(genesis_hash, nonce):
  print "genesis hash found!"
  print "nonce: "        + str(nonce)
  print "genesis hash: " + genesis_hash.encode('hex_codec')


# GOGOGO!
main()