text: #!/usr/bin/env python
  #
  # Electrum - lightweight Bitcoin client
  # Copyright (C) 2014 Thomas Voegtlin
  #
  # Permission is hereby granted, free of charge, to any person
  # obtaining a copy of this software and associated documentation files
  # (the "Software"), to deal in the Software without restriction,
  # including without limitation the rights to use, copy, modify, merge,
  # publish, distribute, sublicense, and/or sell copies of the Software,
  # and to permit persons to whom the Software is furnished to do so,
  # subject to the following conditions:
  #
  # The above copyright notice and this permission notice shall be
  # included in all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  # BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  # ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  # SOFTWARE.
  import asyncio
  import hashlib
  
  from aiorpcx import TaskGroup, run_in_thread
  
  from .transaction import Transaction
  from .util import bh2u, PrintError
  from .bitcoin import address_to_scripthash
  
  
  def history_status(h):
      if not h:
          return None
      status = ''
      for tx_hash, height in h:
          status += tx_hash + ':%d:' % height
      return bh2u(hashlib.sha256(status.encode('ascii')).digest())
  
  
  class Synchronizer(PrintError):
      '''The synchronizer keeps the wallet up-to-date with its set of
      addresses and their transactions.  It subscribes over the network
      to wallet addresses, gets the wallet to generate new addresses
      when necessary, requests the transaction history of any addresses
      we don't have the full history of, and requests binary transaction
      data of any transactions the wallet doesn't have.
      '''
      def __init__(self, wallet):
          self.wallet = wallet
          self.asyncio_loop = wallet.network.asyncio_loop
          self.requested_tx = {}
          self.requested_histories = {}
          self.requested_addrs = set()
          self.scripthash_to_address = {}
          self._processed_some_notifications = False  # so that we don't miss them
          # Queues
          self.add_queue = asyncio.Queue()
          self.status_queue = asyncio.Queue()
  
      def diagnostic_name(self):
          return '{}:{}'.format(self.__class__.__name__, self.wallet.diagnostic_name())
  
      def is_up_to_date(self):
          return (not self.requested_addrs
                  and not self.requested_histories
                  and not self.requested_tx)
  
      def add(self, addr):
          asyncio.run_coroutine_threadsafe(self._add(addr), self.asyncio_loop)
  
      async def _add(self, addr):
          if addr in self.requested_addrs: return
          self.requested_addrs.add(addr)
          await self.add_queue.put(addr)
  
      async def _on_address_status(self, addr, status):
          history = self.wallet.history.get(addr, [])
          if history_status(history) == status:
              return
          if addr in self.requested_histories:
              return
          # request address history
          self.requested_histories[addr] = status
          h = address_to_scripthash(addr)
          result = await self.session.send_request("blockchain.scripthash.get_history", [h])
          self.print_error("receiving history", addr, len(result))
          hashes = set(map(lambda item: item['tx_hash'], result))
          hist = list(map(lambda item: (item['tx_hash'], item['height']), result))
          # tx_fees
          tx_fees = [(item['tx_hash'], item.get('fee')) for item in result]
          tx_fees = dict(filter(lambda x:x[1] is not None, tx_fees))
          # Check that txids are unique
          if len(hashes) != len(result):
              self.print_error("error: server history has non-unique txids: %s"% addr)
          # Check that the status corresponds to what was announced
          elif history_status(hist) != status:
              self.print_error("error: status mismatch: %s" % addr)
          else:
              # Store received history
              self.wallet.receive_history_callback(addr, hist, tx_fees)
              # Request transactions we don't have
              await self._request_missing_txs(hist)
  
          # Remove request; this allows up_to_date to be True
          self.requested_histories.pop(addr)
  
      async def _request_missing_txs(self, hist):
          # "hist" is a list of [tx_hash, tx_height] lists
          transaction_hashes = []
          for tx_hash, tx_height in hist:
              if tx_hash in self.requested_tx:
                  continue
              if tx_hash in self.wallet.transactions:
                  continue
              transaction_hashes.append(tx_hash)
              self.requested_tx[tx_hash] = tx_height
  
          if not transaction_hashes: return
          async with TaskGroup() as group:
              for tx_hash in transaction_hashes:
                  await group.spawn(self._get_transaction, tx_hash)
  
      async def _get_transaction(self, tx_hash):
          result = await self.session.send_request('blockchain.transaction.get', [tx_hash])
          tx = Transaction(result)
          try:
              tx.deserialize()
          except Exception:
              self.print_msg("cannot deserialize transaction, skipping", tx_hash)
              return
          if tx_hash != tx.txid():
              self.print_error("received tx does not match expected txid ({} != {})"
                               .format(tx_hash, tx.txid()))
              return
          tx_height = self.requested_tx.pop(tx_hash)
          self.wallet.receive_tx_callback(tx_hash, tx, tx_height)
          self.print_error("received tx %s height: %d bytes: %d" %
                           (tx_hash, tx_height, len(tx.raw)))
          # callbacks
          self.wallet.network.trigger_callback('new_transaction', self.wallet, tx)
  
      async def send_subscriptions(self, group: TaskGroup):
          async def subscribe_to_address(addr):
              h = address_to_scripthash(addr)
              self.scripthash_to_address[h] = addr
              await self.session.subscribe('blockchain.scripthash.subscribe', [h], self.status_queue)
              self.requested_addrs.remove(addr)
  
          while True:
              addr = await self.add_queue.get()
              await group.spawn(subscribe_to_address, addr)
  
      async def handle_status(self, group: TaskGroup):
          while True:
              h, status = await self.status_queue.get()
              addr = self.scripthash_to_address[h]
              await group.spawn(self._on_address_status, addr, status)
              self._processed_some_notifications = True
  
      @property
      def session(self):
          s = self.wallet.network.interface.session
          assert s is not None
          return s
  
      async def main(self):
          self.wallet.set_up_to_date(False)
          # request missing txns, if any
          for history in self.wallet.history.values():
              # Old electrum servers returned ['*'] when all history for the address
              # was pruned. This no longer happens but may remain in old wallets.
              if history == ['*']: continue
              await self._request_missing_txs(history)
          # add addresses to bootstrap
          for addr in self.wallet.get_addresses():
              await self._add(addr)
          # main loop
          while True:
              await asyncio.sleep(0.1)
              await run_in_thread(self.wallet.synchronize)
              up_to_date = self.is_up_to_date()
              if (up_to_date != self.wallet.is_up_to_date()
                      or up_to_date and self._processed_some_notifications):
                  self._processed_some_notifications = False
                  self.wallet.set_up_to_date(up_to_date)
                  self.wallet.network.trigger_callback('wallet_updated', self.wallet)
  