require 'chef_fs/path_utils'

module ChefFS
  module FileSystem
    class BaseFSObject
      def initialize(name, parent)
        @parent = parent
        @name = name
        if parent
          @path = ChefFS::PathUtils::join(parent.path, name)
        else
          if name != ''
            raise ArgumentError, "Name of root object must be empty string: was '#{name}' instead"
          end
          @path = '/'
        end
      end

      attr_reader :name
      attr_reader :parent
      attr_reader :path

      def root
        parent ? parent.root : self
      end

      def path_for_printing
        if parent
          ChefFS::PathUtils::join(parent.path_for_printing, name)
        else
          name
        end
      end

      def dir?
        false
      end

      def exists?
        true
      end

      def child(name)
        NonexistentFSObject.new(name, self)
      end

      # Override can_have_child? to report whether a given file *could* be added
      # to this directory.  (Some directories can't have subdirs, some can only have .json
      # files, etc.)
      def can_have_child?(name, is_dir)
        false
      end

      # Override this if you have a special comparison algorithm that can tell
      # you whether this entry is the same as another--either a quicker or a
      # more reliable one.  Callers will use this to decide whether to upload,
      # download or diff an object.
      #
      # You should not override this if you're going to do the standard
      # +self.read == other.read+.  If you return +nil+, the caller will call
      # +other.compare_to(you)+ instead.  Give them a chance :)
      #
      # ==== Parameters
      #
      # * +other+ - the entry to compare to
      #
      # ==== Returns
      #
      # * +[ are_same, value, other_value ]+
      #   +are_same+ may be +true+, +false+ or +nil+ (which means "don't know").
      #   +value+ and +other_value+ must either be the text of +self+ or +other+,
      #   +:none+ (if the entry does not exist or has no value) or +nil+ if the
      #   value was not retrieved.
      # * +nil+ if a definitive answer cannot be had and nothing was retrieved.
      #
      # ==== Example
      #
      #     are_same, value, other_value = entry.compare_to(other)
      #     if are_same.nil?
      #       are_same, other_value, value = other.compare_to(entry)
      #     end
      #     if are_same.nil?
      #       value = entry.read if value.nil?
      #       other_value = entry.read if other_value.nil?
      #       are_same = (value == other_value)
      #     end
      def compare_to(other)
        return nil
      end

      # Important directory attributes: name, parent, path, root
      # Overridable attributes: dir?, child(name), path_for_printing
      # Abstract: read, write, delete, children
    end
  end
end