require 'active_support/benchmarkable'

module Harvestdor
  class Indexer::Resource
    include ActiveSupport::Benchmarkable

    attr_reader :indexer, :druid, :options

    # @param [Harvestdor::Indexer] indexer an instance of Harvestdor::Indexer
    # @param [String] druid a druid of the form 'druid:oo123oo1234'
    def initialize(indexer, druid, options = {})
      @indexer = indexer
      @druid = druid
      @options = options
    end

    # @return [String] string of form  oo123oo1234
    def bare_druid
      @bare_druid ||= druid.gsub('druid:', '')
    end

    ##
    # The harvestdor client used for retrieving resources
    def harvestdor_client
      indexer.harvestdor_client
    end

    def dor_fetcher_client
      indexer.dor_fetcher_client
    end

    ##
    # Get the logger
    def logger
      options[:logger] || (indexer.logger if indexer.respond_to? :logger) || Logger.new(STDERR)
    end

    def exists?
      public_xml
    rescue Harvestdor::Errors::MissingPublicXml, Harvestdor::Errors::MissingPurlPage
      false
    end

    ##
    # Is this resource a collection?
    def collection?
      identity_metadata.xpath('/identityMetadata/objectType').any? { |x| x.text == 'collection' }
    end

    # get the druids from isMemberOfCollection relationships in rels-ext from public_xml
    # @return [Array<String>] the druids (e.g. ww123yy1234) this object has isMemberOfColletion relationship with, or nil if none
    def collections
      @collections ||= begin
        ns_hash = { 'rdf' => 'http://www.w3.org/1999/02/22-rdf-syntax-ns#', 'fedora' => 'info:fedora/fedora-system:def/relations-external#', '' => '' }
        is_member_of_nodes ||= public_xml.xpath('/publicObject/rdf:RDF/rdf:Description/fedora:isMemberOfCollection/@rdf:resource', ns_hash)

        is_member_of_nodes.reject { |n| n.value.empty? }.map do |n|
          Harvestdor::Indexer::Resource.new(indexer, n.value.gsub('info:fedora/', ''))
        end
      end
    end

    ##
    # Return the items in this collection
    def items
      return [] unless collection?

      # return an enumerator, with an estimated size of the collection
      return to_enum(:items) { items_druids.length } unless block_given?

      items_druids.each do |x|
        yield Harvestdor::Indexer::Resource.new(indexer, x)
      end
    end

    def items_druids
      @items_druids ||= dor_fetcher_client.druid_array(dor_fetcher_client.get_collection(bare_druid, {}))
    end

    # given a druid, get its objectLabel from its purl page identityMetadata
    # @return [String] the value of the <objectLabel> element in the identityMetadata for the object
    def identity_md_obj_label
      logger.error("#{druid} missing identityMetadata") unless identity_metadata
      identity_metadata.xpath('identityMetadata/objectLabel').text
    end

    # return the MODS for the druid as a Stanford::Mods::Record object
    # @return [Stanford::Mods::Record] created from the MODS xml for the druid
    def smods_rec
      @smods_rec ||= benchmark "smods_rec(#{druid})", level: :debug do
        ng_doc = mods
        raise "Empty MODS metadata for #{druid}: #{ng_doc.to_xml}" if ng_doc.root.xpath('//text()').empty?
        mods_rec = Stanford::Mods::Record.new
        mods_rec.from_nk_node(ng_doc.root)
        mods_rec
      end
    end

    def mods
      @mods ||= harvestdor_client.mods bare_druid
    end

    # the public xml for this DOR object, from the purl page
    # @return [Nokogiri::XML::Document] the public xml for the DOR object
    def public_xml
      @public_xml ||= benchmark "public_xml(#{druid})", level: :debug do
        harvestdor_client.public_xml bare_druid
      end
    end

    ##
    # Has the public_xml been previously retrieved?
    # @deprecated
    def public_xml?
      !!@public_xml
    end

    ##
    # Get the public_xml, if retrieved, or the druid. This is used to short-circuit
    # retrieving metadata out of the public xml.
    # @deprecated
    def public_xml_or_druid
      if public_xml?
        public_xml
      else
        bare_druid
      end
    end

    # the contentMetadata for this DOR object, ultimately from the purl public xml
    # @return [Nokogiri::XML::Document] the contentMetadata for the DOR object
    def content_metadata
      @content_metadata ||= benchmark "content_metadata (#{druid})", level: :debug do
        harvestdor_client.content_metadata public_xml
      end
    end

    # the identityMetadata for this DOR object, ultimately from the purl public xml
    # @return [Nokogiri::XML::Document] the identityMetadata for the DOR object
    def identity_metadata
      @identity_metadata ||= benchmark "identity_metadata (#{druid})", level: :debug do
        harvestdor_client.identity_metadata public_xml
      end
    end

    # the rightsMetadata for this DOR object, ultimately from the purl public xml
    # @return [Nokogiri::XML::Document] the rightsMetadata for the DOR object
    def rights_metadata
      @rights_metadata ||= benchmark "rights_metadata (#{druid})", level: :debug do
        harvestdor_client.rights_metadata public_xml
      end
    end

    # the RDF for this DOR object, ultimately from the purl public xml
    # @return [Nokogiri::XML::Document] the RDF for the DOR object
    def rdf
      @rdf ||= benchmark "rdf (#{druid})", level: :debug do
        harvestdor_client.rdf public_xml
      end
    end

    def eql?(other)
      other.is_a?(Harvestdor::Indexer::Resource) && other.indexer == indexer && other.druid == druid
    end

    def hash
      druid.hash ^ indexer.hash
    end
  end
end