require 'binary_struct'

module NTFS
  #
  # INDEX_HEADER
  #
  # This is the header for indexes, describing the INDEX_ENTRY records, which
  # follow the INDEX_HEADER. Together the index header and the index entries
  # make up a complete index.
  #
  # IMPORTANT NOTE: The offset, length and size structure members are counted
  # relative to the start of the index header structure and not relative to the
  # start of the index root or index allocation structures themselves.
  #

  INDEX_NODE_HEADER = BinaryStruct.new([
    'L',  'entries_offset',     # Byte offset from the INDEX_HEADER to first INDEX_ENTRY, aligned to 8-byte boundary
    'L',  'index_length',       # Data size in byte of the INDEX_ENTRY's, including the INDEX_HEADER, aligned to 8.
    'L',  'allocated_size',     # Offset to end of allocated index entry list buffer (relative to start of node header).

    #
    # For the index root attribute, the above two numbers are always
    # equal, as the attribute is resident and it is resized as needed.
    #
    # For the index allocation attribute, the attribute is not resident
    # and the allocated_size is equal to the index_block_size specified
    # by the corresponding INDEX_ROOT attribute minus the INDEX_BLOCK
    # size not counting the INDEX_HEADER part (i.e. minus -24).
    #

    'L',  'flags',              # See NH_ below.
  ])
  SIZEOF_INDEX_NODE_HEADER = INDEX_NODE_HEADER.size
  # Here follows a list of IndexNodeEntries.

  class IndexNodeHeader
    NH_HAS_CHILDREN = 0x0001

    attr_reader :startEntries, :endEntries, :flags

    def initialize(buf)
      raise "MIQ(NTFS::IndexNodeHeader.initialize) Nil buffer" if buf.nil?
      buf  = buf.read(buf.length) if buf.kind_of?(DataRun)
      @inh = INDEX_NODE_HEADER.decode(buf)

      # Get accessor data.
      @flags        = @inh['flags']
      @endEntries   = @inh['index_length']
      @startEntries = @inh['entries_offset']
    end

    def to_s
      "0x#{'%08x' % @flags}"
    end

    def hasChildren?
      (@flags & NH_HAS_CHILDREN) == NH_HAS_CHILDREN
    end

    def dump
      out = "\#<#{self.class}:0x#{'%08x' % object_id}>\n"
      out << "  Entries Offset   : #{@startEntries}\n"
      out << "  Index Length     : #{@endEntries}\n"
      out << "  Allocated Size   : #{@inh['allocated_size']}\n"
      out << "  Flags            : 0x#{'%08x' % @flags}\n"
      out << "---\n"
    end
  end
end # module NTFS