#!/usr/bin/env python

import sys, hashlib
from electrum import Interface
from electrum.bitcoin import Hash, rev_hex, int_to_hex, hash_encode, hash_decode

"""validate a transaction (SPV)"""

i = Interface({'server':'ecdsa.org:50002:s'})
i.start()


def hash_merkle_root(merkle_s, target_hash, pos):
    h = hash_decode(target_hash)
    for i in range(len(merkle_s)):
        item = merkle_s[i]
        h = Hash( hash_decode(item) + h ) if ((pos >> i) & 1) else Hash( h + hash_decode(item) )
    return hash_encode(h)


def hash_header(res):
    header = int_to_hex(res.get('version'),4) \
        + rev_hex(res.get('prev_block_hash')) \
        + rev_hex(res.get('merkle_root')) \
        + int_to_hex(int(res.get('timestamp')),4) \
        + int_to_hex(int(res.get('bits')),4) \
        + int_to_hex(int(res.get('nonce')),4)
    return rev_hex(Hash(header.decode('hex')).encode('hex'))


def verify_tx(tx_hash):
    
    res = i.synchronous_get([ ('blockchain.transaction.get_merkle',[tx_hash]) ])[0]
    raw_tx = i.synchronous_get([ ('blockchain.transaction.get',[tx_hash, res['block_height']]) ])[0]
    assert hash_encode(Hash(raw_tx.decode('hex'))) == tx_hash

    merkle_root = hash_merkle_root(res['merkle'], tx_hash, res['pos'])
    tx_height = res.get('block_height')
    headers_requests = []
    for height in range(tx_height-10,tx_height+10):
        headers_requests.append( ('blockchain.block.get_header',[height]) )
    headers = i.synchronous_get(headers_requests)
    _hash = None
    for header in headers:
        if _hash: assert _hash == header.get('prev_block_hash')
        _hash = hash_header(header)
        height = header.get('block_height')
        if height==tx_height:
            assert header.get('merkle_root') == merkle_root
            print height, _hash, '*'
        else:
            print height, _hash

try:
    tx = sys.argv[1]
except:
    tx = '587430e52af2cec98b3fd543083469ffa7a5f5dd2bd569898a7897a64e2eb031'

verify_tx(tx)