text: #!/usr/bin/env python3
  # Copyright (c) 2014-2020 The Bitcoin Core developers
  # Distributed under the MIT software license, see the accompanying
  # file COPYING or http://www.opensource.org/licenses/mit-license.php.
  """Helpful routines for regression testing."""
  
  from base64 import b64encode
  from binascii import unhexlify
  from decimal import Decimal, ROUND_DOWN
  from subprocess import CalledProcessError
  import hashlib
  import inspect
  import json
  import logging
  import os
  import re
  import time
  import unittest
  
  from . import coverage
  from .authproxy import AuthServiceProxy, JSONRPCException
  from io import BytesIO
  
  logger = logging.getLogger("TestFramework.utils")
  
  # Assert functions
  ##################
  
  
  def assert_approx(v, vexp, vspan=0.00001):
      """Assert that `v` is within `vspan` of `vexp`"""
      if v < vexp - vspan:
          raise AssertionError("%s < [%s..%s]" % (str(v), str(vexp - vspan), str(vexp + vspan)))
      if v > vexp + vspan:
          raise AssertionError("%s > [%s..%s]" % (str(v), str(vexp - vspan), str(vexp + vspan)))
  
  
  def assert_fee_amount(fee, tx_size, fee_per_kB):
      """Assert the fee was in range"""
      target_fee = round(tx_size * fee_per_kB / 1000, 8)
      if fee < target_fee:
          raise AssertionError("Fee of %s LTC too low! (Should be %s LTC)" % (str(fee), str(target_fee)))
      # allow the wallet's estimation to be at most 2 bytes off
      if fee > (tx_size + 2) * fee_per_kB / 1000:
          raise AssertionError("Fee of %s LTC too high! (Should be %s LTC)" % (str(fee), str(target_fee)))
  
  
  def assert_equal(thing1, thing2, *args):
      if thing1 != thing2 or any(thing1 != arg for arg in args):
          raise AssertionError("not(%s)" % " == ".join(str(arg) for arg in (thing1, thing2) + args))
  
  
  def assert_greater_than(thing1, thing2):
      if thing1 <= thing2:
          raise AssertionError("%s <= %s" % (str(thing1), str(thing2)))
  
  
  def assert_greater_than_or_equal(thing1, thing2):
      if thing1 < thing2:
          raise AssertionError("%s < %s" % (str(thing1), str(thing2)))
  
  
  def assert_raises(exc, fun, *args, **kwds):
      assert_raises_message(exc, None, fun, *args, **kwds)
  
  
  def assert_raises_message(exc, message, fun, *args, **kwds):
      try:
          fun(*args, **kwds)
      except JSONRPCException:
          raise AssertionError("Use assert_raises_rpc_error() to test RPC failures")
      except exc as e:
          if message is not None and message not in e.error['message']:
              raise AssertionError(
                  "Expected substring not found in error message:\nsubstring: '{}'\nerror message: '{}'.".format(
                      message, e.error['message']))
      except Exception as e:
          raise AssertionError("Unexpected exception raised: " + type(e).__name__)
      else:
          raise AssertionError("No exception raised")
  
  
  def assert_raises_process_error(returncode, output, fun, *args, **kwds):
      """Execute a process and asserts the process return code and output.
  
      Calls function `fun` with arguments `args` and `kwds`. Catches a CalledProcessError
      and verifies that the return code and output are as expected. Throws AssertionError if
      no CalledProcessError was raised or if the return code and output are not as expected.
  
      Args:
          returncode (int): the process return code.
          output (string): [a substring of] the process output.
          fun (function): the function to call. This should execute a process.
          args*: positional arguments for the function.
          kwds**: named arguments for the function.
      """
      try:
          fun(*args, **kwds)
      except CalledProcessError as e:
          if returncode != e.returncode:
              raise AssertionError("Unexpected returncode %i" % e.returncode)
          if output not in e.output:
              raise AssertionError("Expected substring not found:" + e.output)
      else:
          raise AssertionError("No exception raised")
  
  
  def assert_raises_rpc_error(code, message, fun, *args, **kwds):
      """Run an RPC and verify that a specific JSONRPC exception code and message is raised.
  
      Calls function `fun` with arguments `args` and `kwds`. Catches a JSONRPCException
      and verifies that the error code and message are as expected. Throws AssertionError if
      no JSONRPCException was raised or if the error code/message are not as expected.
  
      Args:
          code (int), optional: the error code returned by the RPC call (defined
              in src/rpc/protocol.h). Set to None if checking the error code is not required.
          message (string), optional: [a substring of] the error string returned by the
              RPC call. Set to None if checking the error string is not required.
          fun (function): the function to call. This should be the name of an RPC.
          args*: positional arguments for the function.
          kwds**: named arguments for the function.
      """
      assert try_rpc(code, message, fun, *args, **kwds), "No exception raised"
  
  
  def try_rpc(code, message, fun, *args, **kwds):
      """Tries to run an rpc command.
  
      Test against error code and message if the rpc fails.
      Returns whether a JSONRPCException was raised."""
      try:
          fun(*args, **kwds)
      except JSONRPCException as e:
          # JSONRPCException was thrown as expected. Check the code and message values are correct.
          if (code is not None) and (code != e.error["code"]):
              raise AssertionError("Unexpected JSONRPC error code %i" % e.error["code"])
          if (message is not None) and (message not in e.error['message']):
              raise AssertionError(
                  "Expected substring not found in error message:\nsubstring: '{}'\nerror message: '{}'.".format(
                      message, e.error['message']))
          return True
      except Exception as e:
          raise AssertionError("Unexpected exception raised: " + type(e).__name__)
      else:
          return False
  
  
  def assert_is_hex_string(string):
      try:
          int(string, 16)
      except Exception as e:
          raise AssertionError("Couldn't interpret %r as hexadecimal; raised: %s" % (string, e))
  
  
  def assert_is_hash_string(string, length=64):
      if not isinstance(string, str):
          raise AssertionError("Expected a string, got type %r" % type(string))
      elif length and len(string) != length:
          raise AssertionError("String of length %d expected; got %d" % (length, len(string)))
      elif not re.match('[abcdef0-9]+$', string):
          raise AssertionError("String %r contains invalid characters for a hash." % string)
  
  
  def assert_array_result(object_array, to_match, expected, should_not_find=False):
      """
          Pass in array of JSON objects, a dictionary with key/value pairs
          to match against, and another dictionary with expected key/value
          pairs.
          If the should_not_find flag is true, to_match should not be found
          in object_array
          """
      if should_not_find:
          assert_equal(expected, {})
      num_matched = 0
      for item in object_array:
          all_match = True
          for key, value in to_match.items():
              if item[key] != value:
                  all_match = False
          if not all_match:
              continue
          elif should_not_find:
              num_matched = num_matched + 1
          for key, value in expected.items():
              if item[key] != value:
                  raise AssertionError("%s : expected %s=%s" % (str(item), str(key), str(value)))
              num_matched = num_matched + 1
      if num_matched == 0 and not should_not_find:
          raise AssertionError("No objects matched %s" % (str(to_match)))
      if num_matched > 0 and should_not_find:
          raise AssertionError("Objects were found %s" % (str(to_match)))
  
  
  # Utility functions
  ###################
  
  
  def check_json_precision():
      """Make sure json library being used does not lose precision converting BTC values"""
      n = Decimal("20000000.00000003")
      satoshis = int(json.loads(json.dumps(float(n))) * 1.0e8)
      if satoshis != 2000000000000003:
          raise RuntimeError("JSON encode/decode loses precision")
  
  
  def EncodeDecimal(o):
      if isinstance(o, Decimal):
          return str(o)
      raise TypeError(repr(o) + " is not JSON serializable")
  
  
  def count_bytes(hex_string):
      return len(bytearray.fromhex(hex_string))
  
  
  def hex_str_to_bytes(hex_str):
      return unhexlify(hex_str.encode('ascii'))
  
  
  def str_to_b64str(string):
      return b64encode(string.encode('utf-8')).decode('ascii')
  
  
  def satoshi_round(amount):
      return Decimal(amount).quantize(Decimal('0.00000001'), rounding=ROUND_DOWN)
  
  
  def wait_until_helper(predicate, *, attempts=float('inf'), timeout=float('inf'), lock=None, timeout_factor=1.0):
      """Sleep until the predicate resolves to be True.
  
      Warning: Note that this method is not recommended to be used in tests as it is
      not aware of the context of the test framework. Using the `wait_until()` members
      from `BitcoinTestFramework` or `P2PInterface` class ensures the timeout is
      properly scaled. Furthermore, `wait_until()` from `P2PInterface` class in
      `p2p.py` has a preset lock.
      """
      if attempts == float('inf') and timeout == float('inf'):
          timeout = 60
      timeout = timeout * timeout_factor
      attempt = 0
      time_end = time.time() + timeout
  
      while attempt < attempts and time.time() < time_end:
          if lock:
              with lock:
                  if predicate():
                      return
          else:
              if predicate():
                  return
          attempt += 1
          time.sleep(0.05)
  
      # Print the cause of the timeout
      predicate_source = "''''\n" + inspect.getsource(predicate) + "'''"
      logger.error("wait_until() failed. Predicate: {}".format(predicate_source))
      if attempt >= attempts:
          raise AssertionError("Predicate {} not true after {} attempts".format(predicate_source, attempts))
      elif time.time() >= time_end:
          raise AssertionError("Predicate {} not true after {} seconds".format(predicate_source, timeout))
      raise RuntimeError('Unreachable')
  
  def sha256sum_file(filename):
      h = hashlib.sha256()
      with open(filename, 'rb') as f:
          d = f.read(4096)
          while len(d) > 0:
              h.update(d)
              d = f.read(4096)
      return h.digest()
  
  # RPC/P2P connection constants and functions
  ############################################
  
  # The maximum number of nodes a single test can spawn
  MAX_NODES = 12
  # Don't assign rpc or p2p ports lower than this
  PORT_MIN = int(os.getenv('TEST_RUNNER_PORT_MIN', default=11000))
  # The number of ports to "reserve" for p2p and rpc, each
  PORT_RANGE = 5000
  
  
  class PortSeed:
      # Must be initialized with a unique integer for each process
      n = None
  
  
  def get_rpc_proxy(url, node_number, *, timeout=None, coveragedir=None):
      """
      Args:
          url (str): URL of the RPC server to call
          node_number (int): the node number (or id) that this calls to
  
      Kwargs:
          timeout (int): HTTP timeout in seconds
          coveragedir (str): Directory
  
      Returns:
          AuthServiceProxy. convenience object for making RPC calls.
  
      """
      proxy_kwargs = {}
      if timeout is not None:
          proxy_kwargs['timeout'] = int(timeout)
  
      proxy = AuthServiceProxy(url, **proxy_kwargs)
      proxy.url = url  # store URL on proxy for info
  
      coverage_logfile = coverage.get_filename(coveragedir, node_number) if coveragedir else None
  
      return coverage.AuthServiceProxyWrapper(proxy, coverage_logfile)
  
  
  def p2p_port(n):
      assert n <= MAX_NODES
      return PORT_MIN + n + (MAX_NODES * PortSeed.n) % (PORT_RANGE - 1 - MAX_NODES)
  
  
  def rpc_port(n):
      return PORT_MIN + PORT_RANGE + n + (MAX_NODES * PortSeed.n) % (PORT_RANGE - 1 - MAX_NODES)
  
  
  def rpc_url(datadir, i, chain, rpchost):
      rpc_u, rpc_p = get_auth_cookie(datadir, chain)
      host = '127.0.0.1'
      port = rpc_port(i)
      if rpchost:
          parts = rpchost.split(':')
          if len(parts) == 2:
              host, port = parts
          else:
              host = rpchost
      return "http://%s:%s@%s:%d" % (rpc_u, rpc_p, host, int(port))
  
  
  # Node functions
  ################
  
  
  def initialize_datadir(dirname, n, chain):
      datadir = get_datadir_path(dirname, n)
      if not os.path.isdir(datadir):
          os.makedirs(datadir)
      # Translate chain name to config name
      if chain == 'testnet4':
          chain_name_conf_arg = 'testnet'
          chain_name_conf_section = 'test'
      else:
          chain_name_conf_arg = chain
          chain_name_conf_section = chain
      with open(os.path.join(datadir, "litecoin.conf"), 'w', encoding='utf8') as f:
          f.write("{}=1\n".format(chain_name_conf_arg))
          f.write("[{}]\n".format(chain_name_conf_section))
          f.write("port=" + str(p2p_port(n)) + "\n")
          f.write("rpcport=" + str(rpc_port(n)) + "\n")
          f.write("fallbackfee=0.0002\n")
          f.write("server=1\n")
          f.write("keypool=1\n")
          f.write("discover=0\n")
          f.write("dnsseed=0\n")
          f.write("listenonion=0\n")
          f.write("printtoconsole=0\n")
          f.write("upnp=0\n")
          f.write("shrinkdebugfile=0\n")
          os.makedirs(os.path.join(datadir, 'stderr'), exist_ok=True)
          os.makedirs(os.path.join(datadir, 'stdout'), exist_ok=True)
      return datadir
  
  
  def get_datadir_path(dirname, n):
      return os.path.join(dirname, "node" + str(n))
  
  
  def append_config(datadir, options):
      with open(os.path.join(datadir, "litecoin.conf"), 'a', encoding='utf8') as f:
          for option in options:
              f.write(option + "\n")
  
  
  def get_auth_cookie(datadir, chain):
      user = None
      password = None
      if os.path.isfile(os.path.join(datadir, "litecoin.conf")):
          with open(os.path.join(datadir, "litecoin.conf"), 'r', encoding='utf8') as f:
              for line in f:
                  if line.startswith("rpcuser="):
                      assert user is None  # Ensure that there is only one rpcuser line
                      user = line.split("=")[1].strip("\n")
                  if line.startswith("rpcpassword="):
                      assert password is None  # Ensure that there is only one rpcpassword line
                      password = line.split("=")[1].strip("\n")
      try:
          with open(os.path.join(datadir, chain, ".cookie"), 'r', encoding="ascii") as f:
              userpass = f.read()
              split_userpass = userpass.split(':')
              user = split_userpass[0]
              password = split_userpass[1]
      except OSError:
          pass
      if user is None or password is None:
          raise ValueError("No RPC credentials")
      return user, password
  
  
  # If a cookie file exists in the given datadir, delete it.
  def delete_cookie_file(datadir, chain):
      if os.path.isfile(os.path.join(datadir, chain, ".cookie")):
          logger.debug("Deleting leftover cookie file")
          os.remove(os.path.join(datadir, chain, ".cookie"))
  
  
  def softfork_active(node, key):
      """Return whether a softfork is active."""
      return node.getblockchaininfo()['softforks'][key]['active']
  
  
  def set_node_times(nodes, t):
      for node in nodes:
          node.setmocktime(t)
  
  
  # Transaction/Block functions
  #############################
  
  
  def find_output(node, txid, amount, *, blockhash=None):
      """
      Return index to output of txid with value amount
      Raises exception if there is none.
      """
      txdata = node.getrawtransaction(txid, 1, blockhash)
      for i in range(len(txdata["vout"])):
          if txdata["vout"][i]["value"] == amount:
              return i
      raise RuntimeError("find_output txid %s : %s not found" % (txid, str(amount)))
  
  
  # Helper to create at least "count" utxos
  # Pass in a fee that is sufficient for relay and mining new transactions.
  def create_confirmed_utxos(fee, node, count):
      to_generate = int(0.5 * count) + 101
      while to_generate > 0:
          node.generate(min(25, to_generate))
          to_generate -= 25
      utxos = node.listunspent()
      iterations = count - len(utxos)
      addr1 = node.getnewaddress()
      addr2 = node.getnewaddress()
      if iterations <= 0:
          return utxos
      for _ in range(iterations):
          t = utxos.pop()
          inputs = []
          inputs.append({"txid": t["txid"], "vout": t["vout"]})
          outputs = {}
          send_value = t['amount'] - fee
          outputs[addr1] = satoshi_round(send_value / 2)
          outputs[addr2] = satoshi_round(send_value / 2)
          raw_tx = node.createrawtransaction(inputs, outputs)
          signed_tx = node.signrawtransactionwithwallet(raw_tx)["hex"]
          node.sendrawtransaction(signed_tx)
  
      while (node.getmempoolinfo()['size'] > 0):
          node.generate(1)
  
      utxos = node.listunspent()
      assert len(utxos) >= count
      return utxos
  
  
  # Create large OP_RETURN txouts that can be appended to a transaction
  # to make it large (helper for constructing large transactions).
  def gen_return_txouts():
      # Some pre-processing to create a bunch of OP_RETURN txouts to insert into transactions we create
      # So we have big transactions (and therefore can't fit very many into each block)
      # create one script_pubkey
      script_pubkey = "6a4d0200"  # OP_RETURN OP_PUSH2 512 bytes
      for _ in range(512):
          script_pubkey = script_pubkey + "01"
      # concatenate 128 txouts of above script_pubkey which we'll insert before the txout for change
      txouts = []
      from .messages import CTxOut
      txout = CTxOut()
      txout.nValue = 0
      txout.scriptPubKey = hex_str_to_bytes(script_pubkey)
      for _ in range(128):
          txouts.append(txout)
      return txouts
  
  
  # Create a spend of each passed-in utxo, splicing in "txouts" to each raw
  # transaction to make it large.  See gen_return_txouts() above.
  def create_lots_of_big_transactions(node, txouts, utxos, num, fee):
      addr = node.getnewaddress()
      txids = []
      from .messages import CTransaction
      for _ in range(num):
          t = utxos.pop()
          inputs = [{"txid": t["txid"], "vout": t["vout"]}]
          outputs = {}
          change = t['amount'] - fee
          outputs[addr] = satoshi_round(change)
          rawtx = node.createrawtransaction(inputs, outputs)
          tx = CTransaction()
          tx.deserialize(BytesIO(hex_str_to_bytes(rawtx)))
          for txout in txouts:
              tx.vout.append(txout)
          newtx = tx.serialize().hex()
          signresult = node.signrawtransactionwithwallet(newtx, None, "NONE")
          txid = node.sendrawtransaction(signresult["hex"], 0)
          txids.append(txid)
      return txids
  
  
  def mine_large_block(node, utxos=None):
      # generate a 66k transaction,
      # and 14 of them is close to the 1MB block limit
      num = 14
      txouts = gen_return_txouts()
      utxos = utxos if utxos is not None else []
      if len(utxos) < num:
          utxos.clear()
          utxos.extend(node.listunspent())
      fee = 100 * node.getnetworkinfo()["relayfee"]
      create_lots_of_big_transactions(node, txouts, utxos, num, fee=fee)
      node.generate(1)
  
  
  def find_vout_for_address(node, txid, addr):
      """
      Locate the vout index of the given transaction sending to the
      given address. Raises runtime error exception if not found.
      """
      tx = node.getrawtransaction(txid, True)
      for i in range(len(tx["vout"])):
          if any([addr == a for a in tx["vout"][i]["scriptPubKey"]["addresses"]]):
              return i
      raise RuntimeError("Vout not found for address: txid=%s, addr=%s" % (txid, addr))
  
  def modinv(a, n):
      """Compute the modular inverse of a modulo n using the extended Euclidean
      Algorithm. See https://en.wikipedia.org/wiki/Extended_Euclidean_algorithm#Modular_integers.
      """
      # TODO: Change to pow(a, -1, n) available in Python 3.8
      t1, t2 = 0, 1
      r1, r2 = n, a
      while r2 != 0:
          q = r1 // r2
          t1, t2 = t2, t1 - q * t2
          r1, r2 = r2, r1 - q * r2
      if r1 > 1:
          return None
      if t1 < 0:
          t1 += n
      return t1
  
  class TestFrameworkUtil(unittest.TestCase):
      def test_modinv(self):
          test_vectors = [
              [7, 11],
              [11, 29],
              [90, 13],
              [1891, 3797],
              [6003722857, 77695236973],
          ]
  
          for a, n in test_vectors:
              self.assertEqual(modinv(a, n), pow(a, n-2, n))
  