require 'moab_stanford'

module Dor
  class SdrIngestService

    # @param [Dor::Item] dor_item The representation of the digital object
    # @param [String] agreement_id  depreciated, included for backward compatability with common-accessoning
    # @return [void] Create the moab manifests, export data to a BagIt bag, kick off the SDR ingest workflow
    def self.transfer(dor_item, agreement_id=nil)
      druid = dor_item.pid
      workspace = DruidTools::Druid.new(druid,Dor::Config.sdr.local_workspace_root)
      signature_catalog = get_signature_catalog(druid)
      new_version_id = signature_catalog.version_id + 1
      metadata_dir = extract_datastreams(dor_item, workspace)
      verify_version_metadata(metadata_dir, new_version_id)
      version_inventory = get_version_inventory(metadata_dir, druid, new_version_id)
      version_addtions = signature_catalog.version_additions(version_inventory)
      content_addtions = version_addtions.group('content')
      if content_addtions.nil? || content_addtions.files.empty?
        content_dir = nil
      else
        new_file_list = content_addtions.path_list
        content_dir = workspace.find_filelist_parent('content',new_file_list)
      end
      content_group = version_inventory.group('content')
      unless content_group.nil? || content_group.files.empty?
        signature_catalog.normalize_group_signatures(content_group, content_dir)
      end
      # export the bag (in tar format)
      bag_dir = Pathname(Dor::Config.sdr.local_export_home).join(druid.sub('druid:',''))
      bagger = Moab::Bagger.new(version_inventory, signature_catalog, bag_dir)
      bagger.reset_bag
      bagger.create_bag_inventory(:depositor)
      bagger.deposit_group('content', content_dir)
      bagger.deposit_group('metadata', metadata_dir)
      bagger.create_tagfiles
      verify_bag_structure(bag_dir)
      # Now bootstrap SDR workflow. but do not create the workflows datastream
      dor_item.initialize_workflow('sdrIngestWF', false)
    rescue Exception => e
      raise LyberCore::Exceptions::ItemError.new(druid, "Export failure", e)
    end

    # @param [String] druid The object identifier
    # @return [Moab::SignatureCatalog] the catalog of all files previously ingested
    def self.get_signature_catalog(druid)
      sdr_client = Dor::Config.sdr.rest_client
      url = "objects/#{druid}/manifest/signatureCatalog.xml"
      response = sdr_client[url].get
      Moab::SignatureCatalog.parse(response)
    rescue RestClient::ResourceNotFound
      Moab::SignatureCatalog.new(:digital_object_id => druid, :version_id => 0)
    end

    # @param [Dor::Item] dor_item The representation of the digital object
    # @param [DruidTools::Druid] workspace The representation of the item's work area
    # @return [Pathname] Pull all the datastreams specified in the configuration file
    #   into the workspace's metadata directory, overwriting existing file if present
    def self.extract_datastreams(dor_item, workspace)
      metadata_dir = Pathname.new(workspace.path('metadata',create=true))
      Config.sdr.datastreams.to_hash.each_pair do |ds_name, required|
        ds_name = ds_name.to_s
        metadata_file = metadata_dir.join("#{ds_name}.xml")
        metadata_string = self.get_datastream_content(dor_item, ds_name, required)
        metadata_file.open('w') { |f| f << metadata_string } if metadata_string
      end
      metadata_dir
    end

    # @param [Dor::Item] dor_item The representation of the digital object
    # @param [String] ds_name The name of the desired Fedora datastream
    # @param [String] required Enumeration: one of ['required', 'optional']
    # @return [String] return the xml text of the specified datastream if it exists.
    #   If not found, return nil unless it is a required datastream in which case raise exception
    def self.get_datastream_content(dor_item, ds_name, required)
      ds = (ds_name == 'relationshipMetadata' ? 'RELS-EXT' : ds_name)
      if dor_item.datastreams.keys.include?(ds) && ! dor_item.datastreams[ds].new?
        return dor_item.datastreams[ds].content
      elsif (required == 'optional')
        return nil
      else
        raise "required datastream #{ds_name} not found in DOR"
      end
    end

    # @param [Pathname] metadata_dir the location of the metadata directory in the workspace
    # @param [Integer] expected the version identifer expected to be used in the versionMetadata
    def self.verify_version_metadata(metadata_dir, expected)
      vmfile = metadata_dir.join("versionMetadata.xml")
      verify_version_id(vmfile, expected, vmfile_version_id(vmfile))
      true
    end

    # @param [Pathname] pathname The location of the file containing a version number
    # @param [Integer] expected The version number that should be in the file
    # @param [Integer] found The version number that is actually in the file
    def self.verify_version_id(pathname, expected, found)
      raise "Version mismatch in #{pathname}, expected #{expected}, found #{found}" unless (expected == found)
      true
    end

    # @param [Pathname] pathname the location of the versionMetadata file
    # @return [Integer] the versionId found in the last version element, or nil if missing
    def self.vmfile_version_id(pathname)
      verify_pathname(pathname)
      doc = Nokogiri::XML(File.open(pathname.to_s))
      nodeset = doc.xpath("/versionMetadata/version")
      version_id = nodeset.last['versionId']
      version_id.nil? ? nil : version_id.to_i
    end

    # @param [Pathname] metadata_dir The location of the the object's metadata files
    # @param [String] druid The object identifier
    # @param [Integer] version_id The version number
    # @return [Moab::FileInventory] Generate and return a version inventory for the object
    def self.get_version_inventory(metadata_dir, druid, version_id)
      version_inventory = get_content_inventory(metadata_dir, druid, version_id)
      version_inventory.groups << get_metadata_file_group(metadata_dir)
      version_inventory
    end

    # @param [Pathname] metadata_dir The location of the the object's metadata files
    # @param [String] druid The object identifier
    # @param [Integer] version_id The version number
    # @return [Moab::FileInventory] Parse the contentMetadata
    #   and generate a new version inventory object containing a content group
    def self.get_content_inventory(metadata_dir, druid, version_id)
      content_metadata = get_content_metadata(metadata_dir)
      if content_metadata
        Stanford::ContentInventory.new.inventory_from_cm(content_metadata, druid, subset='preserve', version_id)
      else
        FileInventory.new(:type=>"version",:digital_object_id=>druid, :version_id=>version_id)
      end
    end

    # @param [Pathname] metadata_dir The location of the the object's metadata files
    # @return [String] Return the contents of the contentMetadata.xml file from the content directory
    def self.get_content_metadata(metadata_dir)
      content_metadata_pathname = metadata_dir.join('contentMetadata.xml')
      if content_metadata_pathname.exist?
        content_metadata_pathname.read
      else
        nil
      end
    end

    # @param [Pathname] metadata_dir The location of the the object's metadata files
    # @return [Moab::FileGroup] Traverse the metadata directory and generate a metadata group
    def self.get_metadata_file_group(metadata_dir)
      file_group = FileGroup.new(:group_id=>'metadata').group_from_directory(metadata_dir)
      file_group
    end

    # @param [Pathname] bag_dir the location of the bag to be verified
    # @return [Boolean] true if all required files exist, raises exception if not
    def self.verify_bag_structure(bag_dir)
      verify_pathname(bag_dir)
      verify_pathname(bag_dir.join('data'))
      verify_pathname(bag_dir.join('bagit.txt'))
      verify_pathname(bag_dir.join('bag-info.txt'))
      verify_pathname(bag_dir.join('manifest-sha256.txt'))
      verify_pathname(bag_dir.join('tagmanifest-sha256.txt'))
      verify_pathname(bag_dir.join('versionAdditions.xml'))
      verify_pathname(bag_dir.join('versionInventory.xml'))
      verify_pathname(bag_dir.join('data','metadata','versionMetadata.xml'))
      true
    end

    # @param [Pathname] pathname The file whose existence should be verified
    # @return [Boolean] true if file exists, raises exception if not
    def self.verify_pathname(pathname)
      raise "#{pathname.basename} not found at #{pathname}" unless pathname.exist?
      true
    end

  end

end