require 'binary_struct'
require 'fs/ntfs/attrib_file_name'
require 'fs/ntfs/utils'

module NTFS
  DIR_INDEX_NODE = BinaryStruct.new([
    'Q',  'mft_ref',          # MFT file reference for file name (goofy ref).
    'S',  'length',           # Length of entry.
    'S',  'content_len',      # Length of $FILE_NAME attrib
    'L',  'flags',            # See IN_ below (note: these will eventually become general flags)
  ])
  # Here follows a $FILE_NAME attribute if content_len > 0.
  # Last 8 bytes starting on 8 byte boundary are the VCN of the child node in $INDEX_ALLOCATION (if IN_HAS_CHILD is set).
  SIZEOF_DIR_INDEX_NODE = DIR_INDEX_NODE.size

  class DirectoryIndexNode
    IN_HAS_CHILD   = 0x00000001
    IN_LAST_ENTRY  = 0x00000002

    attr_reader :refMft, :length, :contentLen, :flags, :child, :afn, :mftEntry

    def self.nodeFactory(buf)
      nodes = []
      loop do
        node   = DirectoryIndexNode.new(buf)
        buf    = buf[node.length..-1]
        nodes << node
        break if node.isLast?
      end

      nodes
    end

    def initialize(buf)
      raise "MIQ(NTFS::DirectoryIndexNode.initialize) Nil buffer" if buf.nil?
      buf = buf.read(buf.length) if buf.kind_of?(DataRun)
      # Decode the directory index node structure.
      @din = DIR_INDEX_NODE.decode(buf)

      # Get accessor data.
      @mftEntry   = nil
      @refMft     = NTFS::Utils.MkRef(@din['mft_ref'])
      @length     = @din['length']
      @contentLen = @din['content_len']
      @flags      = @din['flags']

      # If there's a $FILE_NAME attrib get it.
      @afn = FileName.new(buf[SIZEOF_DIR_INDEX_NODE, buf.size]) if @contentLen > 0

      # If there's a child node VCN get it.
      if NTFS::Utils.gotBit?(@flags, IN_HAS_CHILD)
        # Child node VCN is located 8 bytes before 'length' bytes.
        # NOTE: If the node has 0 contents, it's offset 16.
        @child = buf[@contentLen == 0 ? 16 : @length - 8, 8].unpack('Q')[0]
      end
    end

    # String rep.
    def to_s
      "\#<#{self.class}:0x#{'%08x' % object_id} name='#{name}'>"
    end

    # Return file name (if resolved).
    def name
      @afn.nil? ? nil : @afn.name
    end

    # Return namespace.
    def namespace
      @afn.nil? ? nil : @afn.namespace
    end

    # Return true if has children.
    def hasChild?
      NTFS::Utils.gotBit?(@flags, IN_HAS_CHILD)
    end

    # Return true if this is the last entry.
    def isLast?
      NTFS::Utils.gotBit?(@flags, IN_LAST_ENTRY)
    end

    # If content is 0, then obviously not a directory.
    def isDir?
      return false if @contentLen == 0
      @mftEntry.isDir?
    end

    # Resolves this node's file reference.
    def resolve(bs)
      if @contentLen > 0
        @mftEntry = bs.mftEntry(@refMft[1])
        raise "MIQ(NTFS::DirectoryIndexNode.resolve) Stale reference: #{inspect}" if @refMft[0] != @mftEntry.sequenceNum
      end
      @mftEntry
    end

    # Dumps object.
    def dump
      out = "\#<#{self.class}:0x#{'%08x' % object_id}>\n"
      out << "  Mft Ref : seq #{@refMft[0]}, entry #{@refMft[1]}\n"
      out << "  Length  : #{@length}\n"
      out << "  Content : #{@contentLen}\n"
      out << "  Flags   : 0x#{'%08x' % @flags}\n"
      out << @afn.dump if @contentLen > 0
      out << "  Child ref: #{@child}\n" if NTFS::Utils.gotBit?(@flags, IN_HAS_CHILD)
      out << "---\n"
    end
  end
end # module NTFS