class ActiveFedora::DelegatedAttribute

def datastream_for_attribute(obj, dsid)
  obj.attached_files[dsid] || raise(ArgumentError, "Undefined datastream id: `#{dsid}' in has_attributes")
end

def initialize(field, dsid, datastream_class, args={})
  self.field = field
  self.dsid = dsid
  self.datastream_class = datastream_class
  self.multiple = args[:multiple].nil? ? false : args[:multiple]
  self.at = args[:at]
end

def primary_solr_name
  @datastream ||= datastream_class.new
  if @datastream.respond_to?(:primary_solr_name)
    @datastream.primary_solr_name(field, dsid)
  else
    raise NoMethodError, "the datastream '#{datastream_class}' doesn't respond to 'primary_solr_name'"
  end
end

def read_om(ds, *opts)
  terminology = at || [field]
  if terminology.length == 1 && opts.present?
    ds.send(terminology.first, *opts)
  else
    ds.send(:term_values, *terminology)
  end
end

def read_rdf(node)
  term = if at
    vals = at.dup
    while vals.length > 1
      node = node.send(vals.shift)
      node = if node.empty?
        node.build
      else
        node.first
      end
    end
    vals.first
  else
    field
  end
  node.send(term)
end

def reader(obj, *opts)
  ds = datastream_for_attribute(obj, dsid)
  if ds.kind_of?(ActiveFedora::RDFDatastream)
    read_rdf(ds)
  else
    read_om(ds, *opts)
  end
end

def type
  if datastream_class.respond_to?(:type)
    datastream_class.type(field)
  else
    raise NoMethodError, "the datastream '#{datastream_class}' doesn't respond to 'type'"
  end
end

def write_om(ds, v)
  terminology = at || [field]
  ds.send(:update_indexed_attributes, {terminology => v})
end

def write_rdf(node, v)
  term = if at
    vals = at.dup
    while vals.length > 1
      node = node.send(vals.shift)
      node = node.build if node.empty?
      node = node.first
    end
    vals.first
  else
    field
  end
  node.send("#{term}=", v)
end

def writer(obj, v)
  ds = datastream_for_attribute(obj, dsid)
  obj.mark_as_changed(field) if obj.value_has_changed?(field, v)
  if ds.kind_of?(ActiveFedora::RDFDatastream)
    write_rdf(ds, v)
  else
    write_om(ds, v)
  end
end