"""The Virtual Hard Disk image (VHDI) 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 VHDIAnalyzerHelper(analyzer_helper.AnalyzerHelper):
    """Virtual Hard Disk image (VHDI) analyzer helper."""

    FORMAT_CATEGORIES = frozenset([definitions.FORMAT_CATEGORY_STORAGE_MEDIA_IMAGE])

    TYPE_INDICATOR = definitions.TYPE_INDICATOR_VHDI

    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)

        # Virtual Hard Disk version 1 (VHD) signature in footer.
        format_specification.AddNewSignature(b"conectix", offset=-512)

        # Virtual Hard Disk version 2 (VHDX) signature in file information.
        format_specification.AddNewSignature(b"vhdxfile", offset=0)

        return format_specification


analyzer.Analyzer.RegisterHelper(VHDIAnalyzerHelper())
