"""The EWF 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 EWFAnalyzerHelper(analyzer_helper.AnalyzerHelper):
    """EWF analyzer helper."""

    FORMAT_CATEGORIES = frozenset(
        [
            definitions.FORMAT_CATEGORY_ARCHIVE,
            definitions.FORMAT_CATEGORY_STORAGE_MEDIA_IMAGE,
        ]
    )

    TYPE_INDICATOR = definitions.TYPE_INDICATOR_EWF

    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)

        # EWF version 1 signature and start of fields.
        format_specification.AddNewSignature(b"EVF\x09\x0d\x0a\xff\x00\x01", offset=0)

        # EWF version 2 signature and major version.
        format_specification.AddNewSignature(b"EVF2\r\n\x81\x00\x02", offset=0)

        return format_specification


analyzer.Analyzer.RegisterHelper(EWFAnalyzerHelper())
