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.
  from threading import Lock
  import hashlib
  
  # from .bitcoin import Hash, hash_encode
  from .transaction import Transaction
  from .util import ThreadJob, bh2u
  
  
  class Synchronizer(ThreadJob):
      '''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.
  
      External interface: __init__() and add() member functions.
      '''
  
      def __init__(self, wallet, network):
          self.wallet = wallet
          self.network = network
          self.new_addresses = set()
          # Entries are (tx_hash, tx_height) tuples
          self.requested_tx = {}
          self.requested_histories = {}
          self.requested_addrs = set()
          self.lock = Lock()
  
          self.initialized = False
          self.initialize()
  
      def parse_response(self, response):
          if response.get('error'):
              self.print_error("response error:", response)
              return None, None
          return response['params'], response['result']
  
      def is_up_to_date(self):
          return (not self.requested_tx and not self.requested_histories
                  and not self.requested_addrs)
  
      def release(self):
          self.network.unsubscribe(self.on_address_status)
  
      def add(self, address):
          '''This can be called from the proxy or GUI threads.'''
          with self.lock:
              self.new_addresses.add(address)
  
      def subscribe_to_addresses(self, addresses):
          if addresses:
              self.requested_addrs |= addresses
              self.network.subscribe_to_addresses(addresses, self.on_address_status)
  
      def get_status(self, 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())
  
      def on_address_status(self, response):
          if self.wallet.synchronizer is None and self.initialized:
              return  # we have been killed, this was just an orphan callback
          params, result = self.parse_response(response)
          if not params:
              return
          addr = params[0]
          history = self.wallet.history.get(addr, [])
          if self.get_status(history) != result:
              if self.requested_histories.get(addr) is None:
                  self.requested_histories[addr] = result
                  self.network.request_address_history(addr, self.on_address_history)
          # remove addr from list only after it is added to requested_histories
          if addr in self.requested_addrs:  # Notifications won't be in
              self.requested_addrs.remove(addr)
  
      def on_address_history(self, response):
          if self.wallet.synchronizer is None and self.initialized:
              return  # we have been killed, this was just an orphan callback
          params, result = self.parse_response(response)
          if not params:
              return
          addr = params[0]
          server_status = self.requested_histories.get(addr)
          if server_status is None:
              self.print_error("receiving history (unsolicited)", addr, len(result))
              return
          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))
          # Note if the server hasn't been patched to sort the items properly
          if hist != sorted(hist, key=lambda x:x[1]):
              self.network.interface.print_error("serving improperly sorted address histories")
          # 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 self.get_status(hist) != server_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
              self.request_missing_txs(hist)
          # Remove request; this allows up_to_date to be True
          self.requested_histories.pop(addr)
  
      def tx_response(self, response):
          if self.wallet.synchronizer is None and self.initialized:
              return  # we have been killed, this was just an orphan callback
          params, result = self.parse_response(response)
          if not params:
              return
          tx_hash = params[0]
          #assert tx_hash == hash_encode(Hash(bytes.fromhex(result)))
          tx = Transaction(result)
          try:
              tx.deserialize()
          except Exception:
              self.print_msg("cannot deserialize transaction, skipping", tx_hash)
              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.network.trigger_callback('new_transaction', tx)
          if not self.requested_tx:
              self.network.trigger_callback('updated')
  
  
      def request_missing_txs(self, hist):
          # "hist" is a list of [tx_hash, tx_height] lists
          requests = []
          for tx_hash, tx_height in hist:
              if tx_hash in self.requested_tx:
                  continue
              if tx_hash in self.wallet.transactions:
                  continue
              requests.append(('blockchain.transaction.get', [tx_hash]))
              self.requested_tx[tx_hash] = tx_height
          self.network.send(requests, self.tx_response)
  
  
      def initialize(self):
          '''Check the initial state of the wallet.  Subscribe to all its
          addresses, and request any transactions in its address history
          we don't have.
          '''
          for history in self.wallet.history.values():
              # Old electrum-dnotes servers returned ['*'] when all history for
              # the address was pruned.  This no longer happens but may
              # remain in old wallets.
              if history == ['*']:
                  continue
              self.request_missing_txs(history)
  
          if self.requested_tx:
              self.print_error("missing tx", self.requested_tx)
          self.subscribe_to_addresses(set(self.wallet.get_addresses()))
          self.initialized = True
  
      def run(self):
          '''Called from the network proxy thread main loop.'''
          # 1. Create new addresses
          self.wallet.synchronize()
  
          # 2. Subscribe to new addresses
          with self.lock:
              addresses = self.new_addresses
              self.new_addresses = set()
          self.subscribe_to_addresses(addresses)
  
          # 3. Detect if situation has changed
          up_to_date = self.is_up_to_date()
          if up_to_date != self.wallet.is_up_to_date():
              self.wallet.set_up_to_date(up_to_date)
              self.network.trigger_callback('updated')
  