text: ###############################################################################
  #
  # The MIT License (MIT)
  #
  # Copyright (c) Crossbar.io Technologies GmbH
  #
  # 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 uuid
  import binascii
  from pprint import pformat
  
  import os
  import cbor2
  import nacl.secret
  import nacl.utils
  import nacl.exceptions
  import nacl.public
  
  import txaio
  from autobahn.wamp.exception import ApplicationError
  from autobahn.wamp.protocol import ApplicationSession
  from ._util import unpack_uint256, pack_uint256
  
  import eth_keys
  
  from ._util import hl, hlval
  from ._eip712_channel_close import sign_eip712_channel_close, recover_eip712_channel_close
  
  
  class Transaction(object):
  
      def __init__(self, channel, delegate, pubkey, key_id, channel_seq, amount, balance, signature):
          self.channel = channel
          self.delegate = delegate
          self.pubkey = pubkey
          self.key_id = key_id
          self.channel_seq = channel_seq
          self.amount = amount
          self.balance = balance
          self.signature = signature
  
      def marshal(self):
          res = {
              'channel': self.channel,
              'delegate': self.delegate,
              'pubkey': self.pubkey,
              'key_id': self.key_id,
              'channel_seq': self.channel_seq,
              'amount': self.amount,
              'balance': self.balance,
              'signature': self.signature,
          }
          return res
  
      def __str__(self):
          return pformat(self.marshal())
  
  
  class SimpleBuyer(object):
      """
      Simple XBR buyer component. This component can be used by a XBR buyer delegate to
      handle the automated buying of data encryption keys from the XBR market maker.
      """
      log = None
  
      def __init__(self, market_maker_adr, buyer_key, max_price):
          """
  
          :param market_maker_adr:
          :type market_maker_adr:
  
          :param buyer_key: Consumer delegate (buyer) private Ethereum key.
          :type buyer_key: bytes
  
          :param max_price: Maximum price we are willing to buy per key.
          :type max_price: int
          """
          assert type(market_maker_adr) == bytes and len(market_maker_adr) == 20, 'market_maker_adr must be bytes[20], but got "{}"'.format(market_maker_adr)
          assert type(buyer_key) == bytes and len(buyer_key) == 32, 'buyer delegate must be bytes[32], but got "{}"'.format(buyer_key)
          assert type(max_price) == int and max_price > 0
  
          self.log = txaio.make_logger()
  
          # market maker address
          self._market_maker_adr = market_maker_adr
          self._xbrmm_config = None
  
          # buyer delegate raw ethereum private key (32 bytes)
          self._pkey_raw = buyer_key
  
          # buyer delegate ethereum private key object
          self._pkey = eth_keys.keys.PrivateKey(buyer_key)
  
          # buyer delegate ethereum private account from raw private key
          # FIXME
          # self._acct = Account.privateKeyToAccount(self._pkey)
          self._acct = None
  
          # buyer delegate ethereum account canonical address
          self._addr = self._pkey.public_key.to_canonical_address()
  
          # buyer delegate ethereum account canonical checksummed address
          # FIXME
          # self._caddr = web3.Web3.toChecksumAddress(self._addr)
          self._caddr = None
  
          # ephemeral data consumer key
          self._receive_key = nacl.public.PrivateKey.generate()
  
          # maximum price per key we are willing to pay
          self._max_price = max_price
  
          # will be filled with on-chain payment channel contract, once started
          self._channel = None
  
          # channel current (off-chain) balance
          self._balance = 0
  
          # channel sequence number
          self._seq = 0
  
          # this holds the keys we bought (map: key_id => nacl.secret.SecretBox)
          self._keys = {}
          self._session = None
          self._running = False
  
          # automatically initiate a close of the payment channel when running into
          # a transaction failing because of insufficient balance remaining in the channel
          self._auto_close_channel = True
  
          # FIXME: poor mans local transaction store
          self._transaction_idx = {}
          self._transactions = []
  
      async def start(self, session, consumer_id):
          """
          Start buying keys to decrypt XBR data by calling ``unwrap()``.
  
          :param session: WAMP session over which to communicate with the XBR market maker.
          :type session: :class:`autobahn.wamp.protocol.ApplicationSession`
  
          :param consumer_id: XBR consumer ID.
          :type consumer_id: str
  
          :return: Current remaining balance in payment channel.
          :rtype: int
          """
          assert isinstance(session, ApplicationSession)
          assert type(consumer_id) == str
          assert not self._running
  
          self._session = session
          self._running = True
  
          self.log.debug('Start buying from consumer delegate address {address} (public key 0x{public_key}..)',
                         address=hl(self._caddr),
                         public_key=binascii.b2a_hex(self._pkey.public_key[:10]).decode())
  
          try:
              self._xbrmm_config = await session.call('xbr.marketmaker.get_config')
  
              # get the currently active (if any) payment channel for the delegate
              assert type(self._addr) == bytes and len(self._addr) == 20
              self._channel = await session.call('xbr.marketmaker.get_active_payment_channel', self._addr)
              if not self._channel:
                  raise Exception('no active payment channel found')
  
              channel_oid = self._channel['channel_oid']
              assert type(channel_oid) == bytes and len(channel_oid) == 16
              self._channel_oid = uuid.UUID(bytes=channel_oid)
  
              # get the current (off-chain) balance of the payment channel
              payment_balance = await session.call('xbr.marketmaker.get_payment_channel_balance', self._channel_oid.bytes)
          except:
              session.leave()
              raise
  
          # FIXME
          if type(payment_balance['remaining']) == bytes:
              payment_balance['remaining'] = unpack_uint256(payment_balance['remaining'])
  
          if not payment_balance['remaining'] > 0:
              raise Exception('no off-chain balance remaining on payment channel')
  
          self._balance = payment_balance['remaining']
          self._seq = payment_balance['seq']
  
          self.log.info('Ok, buyer delegate started [active payment channel {channel_oid} with remaining balance {remaining} at sequence {seq}]',
                        channel_oid=hl(self._channel_oid), remaining=hlval(self._balance), seq=hlval(self._seq))
  
          return self._balance
  
      async def stop(self):
          """
          Stop buying keys.
          """
          assert self._running
  
          self._running = False
  
          self.log.info('Ok, buyer delegate stopped.')
  
      async def balance(self):
          """
          Return current balance of payment channel:
  
          * ``amount``: The initial amount with which the payment channel was opened.
          * ``remaining``: The remaining amount of XBR in the payment channel that can be spent.
          * ``inflight``: The amount of XBR allocated to buy transactions that are currently processed.
  
          :return: Current payment balance.
          :rtype: dict
          """
          assert self._session and self._session.is_attached()
  
          payment_balance = await self._session.call('xbr.marketmaker.get_payment_channel_balance', self._channel['channel_oid'])
  
          return payment_balance
  
      async def open_channel(self, buyer_addr, amount, details=None):
          """
  
          :param amount:
          :type amount:
  
          :param details:
          :type details:
  
          :return:
          :rtype:
          """
          assert self._session and self._session.is_attached()
  
          # FIXME
          signature = os.urandom(64)
  
          payment_channel = await self._session.call('xbr.marketmaker.open_payment_channel',
                                                     buyer_addr,
                                                     self._addr,
                                                     amount,
                                                     signature)
  
          balance = {
              'amount': payment_channel['amount'],
              'remaining': payment_channel['remaining'],
              'inflight': payment_channel['inflight'],
          }
  
          return balance
  
      async def close_channel(self, details=None):
          """
          Requests to close the currently active payment channel.
  
          :return:
          """
  
      async def unwrap(self, key_id, serializer, ciphertext):
          """
          Decrypt XBR data. This functions will potentially make the buyer call the
          XBR market maker to buy data encryption keys from the XBR provider.
  
          :param key_id: ID of the data encryption used for decryption
              of application payload.
          :type key_id: bytes
  
          :param serializer: Application payload serializer.
          :type serializer: str
  
          :param ciphertext: Ciphertext of encrypted application payload to
              decrypt.
          :type ciphertext: bytes
  
          :return: Decrypted application payload.
          :rtype: object
          """
          assert type(key_id) == bytes and len(key_id) == 16
          # FIXME: support more app payload serializers
          assert type(serializer) == str and serializer in ['cbor']
          assert type(ciphertext) == bytes
  
          market_oid = self._channel['market_oid']
          channel_oid = self._channel['channel_oid']
  
          # FIXME
          current_block_number = 1
          verifying_chain_id = self._xbrmm_config['verifying_chain_id']
          verifying_contract_adr = binascii.a2b_hex(self._xbrmm_config['verifying_contract_adr'][2:])
  
          # if we don't have the key, buy it!
          if key_id in self._keys:
              self.log.debug('Key {key_id} already in key store (or currently being bought).',
                             key_id=hl(uuid.UUID(bytes=key_id)))
          else:
              self.log.debug('Key {key_id} not yet in key store - buying key ..', key_id=hl(uuid.UUID(bytes=key_id)))
  
              # mark the key as currently being bought already (the location of code here is multi-entrant)
              self._keys[key_id] = False
  
              # get (current) price for key we want to buy
              quote = await self._session.call('xbr.marketmaker.get_quote', key_id)
  
              # set price we pay set to the (current) quoted price
              amount = unpack_uint256(quote['price'])
  
              self.log.debug('Key {key_id} has current price quote {amount}',
                             key_id=hl(uuid.UUID(bytes=key_id)), amount=hl(int(amount / 10**18)))
  
              if amount > self._max_price:
                  raise ApplicationError('xbr.error.max_price_exceeded',
                                         '{}.unwrap() - key {} needed cannot be bought: price {} exceeds maximum price of {}'.format(self.__class__.__name__, uuid.UUID(bytes=key_id), int(amount / 10 ** 18), int(self._max_price / 10 ** 18)))
  
              # check (locally) we have enough balance left in the payment channel to buy the key
              balance = self._balance - amount
              if balance < 0:
                  if self._auto_close_channel:
                      # FIXME: sign last transaction (from persisted local history)
                      last_tx = None
                      txns = self.past_transactions()
                      if txns:
                          last_tx = txns[0]
  
                      if last_tx:
                          # tx1 is the delegate portion, and tx2 is the market maker portion:
                          # tx1, tx2 = last_tx
                          # close_adr = tx1.channel
                          # close_seq = tx1.channel_seq
                          # close_balance = tx1.balance
                          # close_is_final = True
  
                          close_seq = self._seq
                          close_balance = self._balance
                          close_is_final = True
  
                          signature = sign_eip712_channel_close(self._pkey_raw,
                                                                verifying_chain_id,
                                                                verifying_contract_adr,
                                                                current_block_number,
                                                                market_oid,
                                                                channel_oid,
                                                                close_seq,
                                                                close_balance,
                                                                close_is_final)
  
                          self.log.debug('auto-closing payment channel {channel_oid} [close_seq={close_seq}, close_balance={close_balance}, close_is_final={close_is_final}]',
                                         channel_oid=uuid.UUID(bytes=channel_oid),
                                         close_seq=close_seq,
                                         close_balance=int(close_balance / 10**18),
                                         close_is_final=close_is_final)
  
                          # call market maker to initiate closing of payment channel
                          await self._session.call('xbr.marketmaker.close_channel',
                                                   channel_oid,
                                                   verifying_chain_id,
                                                   current_block_number,
                                                   verifying_contract_adr,
                                                   pack_uint256(close_balance),
                                                   close_seq,
                                                   close_is_final,
                                                   signature)
  
                          # FIXME: wait for and acquire new payment channel instead of bailing out ..
  
                          raise ApplicationError('xbr.error.channel_closed',
                                                 '{}.unwrap() - key {} cannot be bought: payment channel {} ran empty and we initiated close at remaining balance of {}'.format(self.__class__.__name__,
                                                                                                                                                                                uuid.UUID(bytes=key_id),
                                                                                                                                                                                channel_oid,
                                                                                                                                                                                int(close_balance / 10 ** 18)))
                  raise ApplicationError('xbr.error.insufficient_balance',
                                         '{}.unwrap() - key {} cannot be bought: insufficient balance {} in payment channel for amount {}'.format(self.__class__.__name__,
                                                                                                                                                  uuid.UUID(bytes=key_id),
                                                                                                                                                  int(self._balance / 10 ** 18),
                                                                                                                                                  int(amount / 10 ** 18)))
  
              buyer_pubkey = self._receive_key.public_key.encode(encoder=nacl.encoding.RawEncoder)
              channel_seq = self._seq + 1
              is_final = False
  
              # XBRSIG[1/8]: compute EIP712 typed data signature
              signature = sign_eip712_channel_close(self._pkey_raw, verifying_chain_id, verifying_contract_adr,
                                                    current_block_number, market_oid, channel_oid, channel_seq,
                                                    balance, is_final)
  
              # persist 1st phase of the transaction locally
              self._save_transaction_phase1(channel_oid, self._addr, buyer_pubkey, key_id, channel_seq, amount, balance, signature)
  
              # call the market maker to buy the key
              try:
                  receipt = await self._session.call('xbr.marketmaker.buy_key',
                                                     self._addr,
                                                     buyer_pubkey,
                                                     key_id,
                                                     channel_oid,
                                                     channel_seq,
                                                     pack_uint256(amount),
                                                     pack_uint256(balance),
                                                     signature)
              except ApplicationError as e:
                  if e.error == 'xbr.error.channel_closed':
                      self.stop()
                  raise e
              except Exception as e:
                  self.log.error('Encountered error while calling market maker to buy key!')
                  self.log.failure()
                  self._keys[key_id] = e
                  raise e
  
              # XBRSIG[8/8]: check market maker signature
              marketmaker_signature = receipt['signature']
              marketmaker_channel_seq = receipt['channel_seq']
              marketmaker_amount_paid = unpack_uint256(receipt['amount_paid'])
              marketmaker_remaining = unpack_uint256(receipt['remaining'])
              marketmaker_inflight = unpack_uint256(receipt['inflight'])
  
              signer_address = recover_eip712_channel_close(verifying_chain_id, verifying_contract_adr,
                                                            current_block_number, market_oid, channel_oid,
                                                            marketmaker_channel_seq, marketmaker_remaining,
                                                            False, marketmaker_signature)
              if signer_address != self._market_maker_adr:
                  self.log.warn('{klass}.unwrap()::XBRSIG[8/8] - EIP712 signature invalid: signer_address={signer_address}, delegate_adr={delegate_adr}',
                                klass=self.__class__.__name__,
                                signer_address=hl(binascii.b2a_hex(signer_address).decode()),
                                delegate_adr=hl(binascii.b2a_hex(self._market_maker_adr).decode()))
                  raise ApplicationError('xbr.error.invalid_signature',
                                         '{}.unwrap()::XBRSIG[8/8] - EIP712 signature invalid or not signed by market maker'.format(self.__class__.__name__))
  
              if self._seq + 1 != marketmaker_channel_seq:
                  raise ApplicationError('xbr.error.invalid_transaction',
                                         '{}.buy_key(): invalid transaction (channel sequence number mismatch - expected {}, but got {})'.format(self.__class__.__name__, self._seq, receipt['channel_seq']))
  
              if self._balance - amount != marketmaker_remaining:
                  raise ApplicationError('xbr.error.invalid_transaction',
                                         '{}.buy_key(): invalid transaction (channel remaining amount mismatch - expected {}, but got {})'.format(self.__class__.__name__, self._balance - amount, receipt['remaining']))
  
              self._seq = marketmaker_channel_seq
              self._balance = marketmaker_remaining
  
              # persist 2nd phase of the transaction locally
              self._save_transaction_phase2(channel_oid, self._market_maker_adr, buyer_pubkey, key_id, marketmaker_channel_seq,
                                            marketmaker_amount_paid, marketmaker_remaining, marketmaker_signature)
  
              # unseal the data encryption key
              sealed_key = receipt['sealed_key']
              unseal_box = nacl.public.SealedBox(self._receive_key)
              try:
                  key = unseal_box.decrypt(sealed_key)
              except nacl.exceptions.CryptoError as e:
                  self._keys[key_id] = e
                  raise ApplicationError('xbr.error.decryption_failed', '{}.unwrap() - could not unseal data encryption key: {}'.format(self.__class__.__name__, e))
  
              # remember the key, so we can use it to actually decrypt application payload data
              self._keys[key_id] = nacl.secret.SecretBox(key)
  
              transactions_count = self.count_transactions()
              self.log.info(
                  '{klass}.unwrap() - {tx_type} key {key_id} bought for {amount_paid} [payment_channel={payment_channel}, remaining={remaining}, inflight={inflight}, buyer_pubkey={buyer_pubkey}, transactions={transactions}]',
                  klass=self.__class__.__name__,
                  tx_type=hl('XBR BUY   ', color='magenta'),
                  key_id=hl(uuid.UUID(bytes=key_id)),
                  amount_paid=hl(str(int(marketmaker_amount_paid / 10 ** 18)) + ' XBR', color='magenta'),
                  payment_channel=hl(binascii.b2a_hex(receipt['payment_channel']).decode()),
                  remaining=hl(int(marketmaker_remaining / 10 ** 18)),
                  inflight=hl(int(marketmaker_inflight / 10 ** 18)),
                  buyer_pubkey=hl(binascii.b2a_hex(buyer_pubkey).decode()),
                  transactions=transactions_count)
  
          # if the key is already being bought, wait until the one buying path of execution has succeeded and done
          log_counter = 0
          while self._keys[key_id] is False:
              if log_counter % 100:
                  self.log.debug('{klass}.unwrap() - waiting for key "{key_id}" currently being bought ..',
                                 klass=self.__class__.__name__, key_id=hl(uuid.UUID(bytes=key_id)))
                  log_counter += 1
              await txaio.sleep(.2)
  
          # check if the key buying failed and fail the unwrapping in turn
          if isinstance(self._keys[key_id], Exception):
              e = self._keys[key_id]
              raise e
  
          # now that we have the data encryption key, decrypt the application payload
          # the decryption key here is an instance of nacl.secret.SecretBox
          try:
              message = self._keys[key_id].decrypt(ciphertext)
          except nacl.exceptions.CryptoError as e:
              # Decryption failed. Ciphertext failed verification
              raise ApplicationError('xbr.error.decryption_failed', '{}.unwrap() - failed to unwrap encrypted data: {}'.format(self.__class__.__name__, e))
  
          # deserialize the application payload
          # FIXME: support more app payload serializers
          try:
              payload = cbor2.loads(message)
          except cbor2.decoder.CBORDecodeError as e:
              # premature end of stream (expected to read 4187 bytes, got 27 instead)
              raise ApplicationError('xbr.error.deserialization_failed', '{}.unwrap() - failed to deserialize application payload: {}'.format(self.__class__.__name__, e))
  
          return payload
  
      def _save_transaction_phase1(self, channel_oid, delegate_adr, buyer_pubkey, key_id, channel_seq, amount, balance, signature):
          """
  
          :param channel_oid:
          :param delegate_adr:
          :param buyer_pubkey:
          :param key_id:
          :param channel_seq:
          :param amount:
          :param balance:
          :param signature:
          :return:
          """
          if key_id in self._transaction_idx:
              raise RuntimeError('save_transaction_phase1: duplicate transaction for key 0x{}'.format(binascii.b2a_hex(key_id)))
  
          tx1 = Transaction(channel_oid, delegate_adr, buyer_pubkey, key_id, channel_seq, amount, balance, signature)
  
          key_idx = len(self._transactions)
          self._transactions.append([tx1, None])
          self._transaction_idx[key_id] = key_idx
  
      def _save_transaction_phase2(self, channel_oid, delegate_adr, buyer_pubkey, key_id, channel_seq, amount, balance, signature):
          """
  
          :param channel_oid:
          :param delegate_adr:
          :param buyer_pubkey:
          :param key_id:
          :param channel_seq:
          :param amount:
          :param balance:
          :param signature:
          :return:
          """
          if key_id not in self._transaction_idx:
              raise RuntimeError('save_transaction_phase2: transaction for key 0x{} not found'.format(binascii.b2a_hex(key_id)))
  
          key_idx = self._transaction_idx[key_id]
  
          if self._transactions[key_idx][1]:
              raise RuntimeError(
                  'save_transaction_phase2: duplicate transaction for key 0x{}'.format(binascii.b2a_hex(key_id)))
  
          tx1 = self._transactions[key_idx][0]
          tx2 = Transaction(channel_oid, delegate_adr, buyer_pubkey, key_id, channel_seq, amount, balance, signature)
  
          assert tx1.channel == tx2.channel
          # assert tx1.delegate == tx2.delegate
          assert tx1.pubkey == tx2.pubkey
          assert tx1.key_id == tx2.key_id
          assert tx1.channel_seq == tx2.channel_seq
          assert tx1.amount == tx2.amount
          assert tx1.balance == tx2.balance
  
          # note: signatures will differ (obviously)!
          assert tx1.signature != tx2.signature
  
          self._transactions[key_idx][1] = tx2
  
      def past_transactions(self, filter_complete=True, limit=1):
          """
  
          :param filter_complete:
          :param limit:
          :return:
          """
          assert type(filter_complete) == bool
          assert type(limit) == int and limit > 0
  
          n = 0
          res = []
          while n < limit:
              if len(self._transactions) > n:
                  tx = self._transactions[-n]
                  if not filter_complete or (tx[0] and tx[1]):
                      res.append(tx)
                      n += 1
              else:
                  break
          return res
  
      def count_transactions(self):
          """
  
          :return:
          """
          res = {
              'complete': 0,
              'pending': 0,
          }
          for tx1, tx2 in self._transactions:
              if tx1 and tx2:
                  res['complete'] += 1
              else:
                  res['pending'] += 1
          return res
  
      def get_transaction(self, key_id):
          """
  
          :param key_id:
          :return:
          """
          idx = self._transaction_idx.get(key_id, None)
          if idx:
              return self._transactions[idx]
  
      def is_complete(self, key_id):
          """
  
          :param key_id:
          :return:
          """
          idx = self._transaction_idx.get(key_id, None)
          if idx:
              tx1, tx2 = self._transactions[idx]
              return tx1 and tx2
          return False
  