"""Text parser plugin for vsftpd log files."""

import pyparsing

from dfdatetime import time_elements as dfdatetime_time_elements

from plaso.containers import events
from plaso.lib import errors
from plaso.parsers import text_parser
from plaso.parsers.text_plugins import interface


class VsftpdLogEventData(events.EventData):
    """Vsftpd log event data.

    Attributes:
      added_time (dfdatetime.DateTimeValues): date and time the log entry
          was added.
      text (str): vsftpd log message.
    """

    DATA_TYPE = "vsftpd:log"

    def __init__(self):
        """Initializes event data."""
        super().__init__(data_type=self.DATA_TYPE)
        self.added_time = None
        self.text = None


class VsftpdLogTextPlugin(interface.TextPlugin):
    """Text parser plugin for vsftpd log files."""

    NAME = "vsftpd"
    DATA_FORMAT = "vsftpd log file"

    _MONTH_DICT = {
        "jan": 1,
        "feb": 2,
        "mar": 3,
        "apr": 4,
        "may": 5,
        "jun": 6,
        "jul": 7,
        "aug": 8,
        "sep": 9,
        "oct": 10,
        "nov": 11,
        "dec": 12,
    }

    _ONE_OR_TWO_DIGITS = pyparsing.Word(pyparsing.nums, max=2).set_parse_action(
        lambda tokens: int(tokens[0], 10)
    )

    _TWO_DIGITS = pyparsing.Word(pyparsing.nums, exact=2).set_parse_action(
        lambda tokens: int(tokens[0], 10)
    )

    _FOUR_DIGITS = pyparsing.Word(pyparsing.nums, exact=4).set_parse_action(
        lambda tokens: int(tokens[0], 10)
    )

    _THREE_LETTERS = pyparsing.Word(pyparsing.alphas, exact=3)

    # Date and time values are formatted as: Mon Jun  6 18:43:28 2016
    _DATE_TIME = pyparsing.Group(
        _THREE_LETTERS
        + _THREE_LETTERS
        + _ONE_OR_TWO_DIGITS
        + _TWO_DIGITS
        + pyparsing.Suppress(":")
        + _TWO_DIGITS
        + pyparsing.Suppress(":")
        + _TWO_DIGITS
        + _FOUR_DIGITS
    )

    _END_OF_LINE = pyparsing.Suppress(pyparsing.LineEnd())

    _LOG_LINE = (
        _DATE_TIME.set_results_name("date_time")
        + pyparsing.restOfLine().set_results_name("text")
        + _END_OF_LINE
    )

    _LINE_STRUCTURES = [("log_line", _LOG_LINE)]

    VERIFICATION_GRAMMAR = _LOG_LINE

    def _ParseRecord(self, parser_mediator, key, structure):
        """Parses a pyparsing structure.

        Args:
          parser_mediator (ParserMediator): mediates interactions between parsers
              and other components, such as storage and dfVFS.
          key (str): name of the parsed structure.
          structure (pyparsing.ParseResults): tokens from a parsed log line.

        Raises:
          ParseError: if the structure cannot be parsed.
        """
        time_elements_structure = self._GetValueFromStructure(structure, "date_time")

        event_data = VsftpdLogEventData()
        event_data.added_time = self._ParseTimeElements(time_elements_structure)
        # TODO: extract pid and username.
        event_data.text = self._GetStringValueFromStructure(structure, "text")

        parser_mediator.ProduceEventData(event_data)

    def _ParseTimeElements(self, time_elements_structure):
        """Parses date and time elements of a log line.

        Args:
          time_elements_structure (pyparsing.ParseResults): date and time elements
              of a log line.

        Returns:
          dfdatetime.TimeElements: date and time value.

        Raises:
          ParseError: if a valid date and time value cannot be derived from
              the time elements.
        """
        try:
            _, month_string, day_of_month, hours, minutes, seconds, year = (
                time_elements_structure
            )

            month = self._MONTH_DICT.get(month_string.lower(), 0)

            time_elements_tuple = (year, month, day_of_month, hours, minutes, seconds)
            date_time = dfdatetime_time_elements.TimeElements(
                time_elements_tuple=time_elements_tuple
            )
            date_time.is_local_time = True

            return date_time

        except (IndexError, TypeError, ValueError) as exception:
            raise errors.ParseError(
                f"Unable to parse time elements with error: {exception!s}"
            )

    def CheckRequiredFormat(self, parser_mediator, text_reader):
        """Check if the log record has the minimal structure required by the plugin.

        Args:
          parser_mediator (ParserMediator): mediates interactions between parsers
              and other components, such as storage and dfVFS.
          text_reader (EncodedTextReader): text reader.

        Returns:
          bool: True if this is the correct plugin, False otherwise.
        """
        try:
            structure = self._VerifyString(text_reader.lines)
        except errors.ParseError:
            return False

        time_elements_structure = self._GetValueFromStructure(structure, "date_time")

        try:
            self._ParseTimeElements(time_elements_structure)
        except errors.ParseError:
            return False

        return True


text_parser.TextLogParser.RegisterPlugin(VsftpdLogTextPlugin)
