"""The BZIP2 format analyzer helper implementation."""

from dfvfs.analyzer import analyzer
from dfvfs.analyzer import analyzer_helper
from dfvfs.analyzer import specification
from dfvfs.lib import definitions


class BZIP2AnalyzerHelper(analyzer_helper.AnalyzerHelper):
    """BZIP2 analyzer helper."""

    FORMAT_CATEGORIES = frozenset([definitions.FORMAT_CATEGORY_COMPRESSED_STREAM])

    TYPE_INDICATOR = definitions.TYPE_INDICATOR_BZIP2

    def GetFormatSpecification(self):
        """Retrieves the format specification.

        Returns:
          FormatSpecification: format specification or None if the format cannot
              be defined by a specification object.
        """
        format_specification = specification.FormatSpecification(self.type_indicator)

        # TODO: add support for signature chains so that we add the 'BZ' at
        # offset 0.

        # BZIP2 compressed steam signature.
        format_specification.AddNewSignature(b"\x31\x41\x59\x26\x53\x59", offset=4)

        return format_specification


analyzer.Analyzer.RegisterHelper(BZIP2AnalyzerHelper())
