# Copyright 2013, Damian Johnson and The Tor Project
# See LICENSE for licensing information

"""
Parsing for `TorDNSEL <https://www.torproject.org/projects/tordnsel.html.en>`_
exit list files.
"""

import datetime

import stem.util.connection
import stem.util.str_tools
import stem.util.tor_tools

from stem.descriptor import (
  Descriptor,
  _read_until_keywords,
  _get_descriptor_components,
)


def _parse_file(tordnsel_file, validate = True, **kwargs):
  """
  Iterates over a tordnsel file.

  :returns: iterator for :class:`~stem.descriptor.tordnsel.TorDNSEL`
    instances in the file

  :raises:
    * **ValueError** if the contents is malformed and validate is **True**
    * **IOError** if the file can't be read
  """

  # skip content prior to the first ExitNode
  _read_until_keywords("ExitNode", tordnsel_file, skip = True)

  while True:
    contents = _read_until_keywords("ExitAddress", tordnsel_file)
    contents += _read_until_keywords("ExitNode", tordnsel_file)

    if contents:
      yield TorDNSEL(bytes.join(b"", contents), validate, **kwargs)
    else:
      break  # done parsing file


class TorDNSEL(Descriptor):
  """
  TorDNSEL descriptor (`exitlist specification
  <https://www.torproject.org/tordnsel/exitlist-spec.txt>`_)

  :var str fingerprint: **\*** authority's fingerprint
  :var datetime published: **\*** time in UTC when this descriptor was made
  :var datetime last_status: **\*** time in UTC when the relay was seen in a v2 network status
  :var list exit_addresses: **\*** list of (str address, datetime date) tuples consisting of the found IPv4 exit address and the time

  **\*** attribute is either required when we're parsed with validation or has
  a default value, others are left as **None** if undefined
  """

  def __init__(self, raw_contents, validate):
    super(TorDNSEL, self).__init__(raw_contents)
    raw_contents = stem.util.str_tools._to_unicode(raw_contents)
    entries = _get_descriptor_components(raw_contents, validate)

    self.fingerprint = None
    self.published = None
    self.last_status = None
    self.exit_addresses = []

    self._parse(entries, validate)

  def _parse(self, entries, validate):

    for keyword, values in entries.items():
      value, block_content = values[0]

      if validate and block_content:
        raise ValueError("Unexpected block content: %s" % block_content)

      if keyword == "ExitNode":
        if validate and not stem.util.tor_tools.is_valid_fingerprint(value):
          raise ValueError("Tor relay fingerprints consist of forty hex digits: %s" % value)

        self.fingerprint = value
      elif keyword == "Published":
        try:
          self.published = datetime.datetime.strptime(value, "%Y-%m-%d %H:%M:%S")
        except ValueError:
          if validate:
            raise ValueError("Published time wasn't parsable: %s" % value)
      elif keyword == "LastStatus":
        try:
          self.last_status = datetime.datetime.strptime(value, "%Y-%m-%d %H:%M:%S")
        except ValueError:
          if validate:
            raise ValueError("LastStatus time wasn't parsable: %s" % value)
      elif keyword == "ExitAddress":
        for value, block_content in values:
          address, date = value.split(" ", 1)

          if validate:
            if not stem.util.connection.is_valid_ipv4_address(address):
              raise ValueError("ExitAddress isn't a valid IPv4 address: %s" % address)
            elif block_content:
              raise ValueError("Unexpected block content: %s" % block_content)

          try:
            date = datetime.datetime.strptime(date, "%Y-%m-%d %H:%M:%S")
            self.exit_addresses.append((address, date))
          except ValueError:
            if validate:
              raise ValueError("ExitAddress found time wasn't parsable: %s" % value)
      elif validate:
        raise ValueError("Unrecognized keyword: %s" % keyword)