Class: Dor::TechnicalMetadataService

Inherits:
Object
  • Object
show all
Defined in:
lib/dor/services/technical_metadata_service.rb

Class Method Summary collapse

Class Method Details

.add_update_technical_metadata(dor_item) ⇒ Boolean

Returns True if technical metadata is correctly added or updated.

Parameters:

  • dor_item (Dor::Item) —

    The DOR item being processed by the technical metadata robot

Returns:

  • (Boolean) —

    True if technical metadata is correctly added or updated



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# File 'lib/dor/services/technical_metadata_service.rb', line 11

def self.add_update_technical_metadata(dor_item)
  test_jhove_service
  druid = dor_item.pid
  content_group_diff = get_content_group_diff(dor_item)
  deltas = get_file_deltas(content_group_diff)
  new_files = get_new_files(deltas)
  old_techmd = get_old_technical_metadata(dor_item)
  new_techmd = get_new_technical_metadata(druid, new_files)
  if old_techmd.nil?
    # this is version 1 or previous technical metadata was not saved
    final_techmd = new_techmd
  elsif content_group_diff.difference_count == 0
    # there have been no changes to content files from previous version
    return true
  else
    merged_nodes = merge_file_nodes(old_techmd, new_techmd, deltas)
    final_techmd = build_technical_metadata(druid, merged_nodes)
  end
  ds = dor_item.datastreams['technicalMetadata']
  ds.dsLabel = 'Technical Metadata'
  ds.content = final_techmd
  ds.save
  true
end

.build_technical_metadata(druid, merged_nodes) ⇒ String

Returns The finalized technicalMetadata datastream contents for the new object version.

Parameters:

  • druid (String) —

    The identifier of the digital object being processed by the technical metadata robot

  • merged_nodes (Hash<String,Nokogiri::XML::Node>) —

    The complete set of technicalMetadata nodes for the digital object, indexed by filename

Returns:

  • (String) —

    The finalized technicalMetadata datastream contents for the new object version



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# File 'lib/dor/services/technical_metadata_service.rb', line 190

def self.build_technical_metadata(druid, merged_nodes)
  techmd_root = <<-EOF
<technicalMetadata objectId='#{druid}' datetime='#{Time.now.utc.iso8601}'
xmlns:jhove='http://hul.harvard.edu/ois/xml/ns/jhove'
xmlns:mix='http://www.loc.gov/mix/v10'
xmlns:textmd='info:lc/xmlns/textMD-v3'>
  EOF
  doc = techmd_root
  merged_nodes.keys.sort.each {|path| doc << merged_nodes[path] }
  doc + '</technicalMetadata>'
end

.get_content_group_diff(dor_item) ⇒ FileGroupDifference

Returns The differences between two versions of a group of files.

Parameters:

  • dor_item (Dor::Item) —

    The DOR item being processed by the technical metadata robot

Returns:

  • (FileGroupDifference) —

    The differences between two versions of a group of files



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# File 'lib/dor/services/technical_metadata_service.rb', line 50

def self.get_content_group_diff(dor_item)
  inventory_diff = dor_item.get_content_diff('all')
  inventory_diff.group_difference('content')
rescue Dor::Exception # no contentMetadata
  Moab::FileGroupDifference.new
end

.get_dor_technical_metadata(dor_item) ⇒ String

Returns The technicalMetadata datastream from the previous version of the digital object (fetched from DOR fedora). The data is updated to the latest format.

Parameters:

  • dor_item (Dor::Item) —

    The DOR item being processed by the technical metadata robot

Returns:

  • (String) —

    The technicalMetadata datastream from the previous version of the digital object (fetched from DOR fedora). The data is updated to the latest format.



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# File 'lib/dor/services/technical_metadata_service.rb', line 90

def self.get_dor_technical_metadata(dor_item)
  ds = 'technicalMetadata'
  return nil unless dor_item.datastreams.keys.include?(ds) && !dor_item.datastreams[ds].new?
  dor_techmd = dor_item.datastreams[ds].content
  return dor_techmd if dor_techmd =~ /<technicalMetadata/
  return ::JhoveService.new.upgrade_technical_metadata(dor_techmd) if dor_techmd =~ /<jhove/
  nil
end

.get_file_deltas(content_group_diff) ⇒ Hash<Symbol,Array>

Returns Sets of filenames grouped by change type for use in performing file or metadata operations.

Parameters:

  • content_group_diff (FileGroupDifference)

Returns:

  • (Hash<Symbol,Array>) —

    Sets of filenames grouped by change type for use in performing file or metadata operations



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# File 'lib/dor/services/technical_metadata_service.rb', line 59

def self.get_file_deltas(content_group_diff)
  content_group_diff.file_deltas
end

.get_file_nodes(technical_metadata) ⇒ Hash<String,Nokogiri::XML::Node>

Returns The set of nodes from a technicalMetadata datastream, indexed by filename.

Parameters:

  • technical_metadata (String) —

    A technicalMetadata datastream contents

Returns:

  • (Hash<String,Nokogiri::XML::Node>) —

    The set of nodes from a technicalMetadata datastream, indexed by filename



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# File 'lib/dor/services/technical_metadata_service.rb', line 163

def self.get_file_nodes(technical_metadata)
  file_hash = {}
  return file_hash if technical_metadata.nil?
  current_file = []
  path = nil
  in_file = false
  technical_metadata.each_line do |line|
    if line =~ /^\s*<file.*["'](.*?)["']/
      current_file << line
      path = $1
      in_file = true
    elsif line =~ /^\s*<\/file>/
      current_file << line
      file_hash[path] = current_file.join
      current_file = []
      path = nil
      in_file = false
    elsif in_file
      current_file << line
    end
  end
  file_hash
end

.get_new_files(deltas) ⇒ Array<String>

Returns The list of filenames for files that are either added or modifed since the previous version.

Parameters:

  • deltas (Hash<Symbol,Array>) —

    Sets of filenames grouped by change type for use in performing file or metadata operations

Returns:

  • (Array<String>) —

    The list of filenames for files that are either added or modifed since the previous version



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# File 'lib/dor/services/technical_metadata_service.rb', line 65

def self.get_new_files(deltas)
  deltas[:added] + deltas[:modified]
end

.get_new_technical_metadata(druid, new_files) ⇒ String

Returns The technicalMetadata datastream for the new files of the new digital object version.

Parameters:

  • druid (DruidTools::Druid) —

    A wrapper class for the druid identifier. Used to generate paths

  • new_files (Array<String>) —

    The list of filenames for files that are either added or modifed since the previous version

Returns:

  • (String) —

    The technicalMetadata datastream for the new files of the new digital object version



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# File 'lib/dor/services/technical_metadata_service.rb', line 109

def self.get_new_technical_metadata(druid, new_files)
  return nil if new_files.nil? || new_files.empty?
  workspace = DruidTools::Druid.new(druid, Dor::Config.sdr.local_workspace_root)
  content_dir = workspace.find_filelist_parent('content', new_files)
  temp_dir = workspace.temp_dir
  jhove_service = ::JhoveService.new(temp_dir)
  jhove_service.digital_object_id = druid
  fileset_file = write_fileset(temp_dir, new_files)
  jhove_output_file = jhove_service.run_jhove(content_dir, fileset_file)
  tech_md_file = jhove_service.create_technical_metadata(jhove_output_file)
  IO.read(tech_md_file)
end

.get_old_technical_metadata(dor_item) ⇒ String

Returns The technicalMetadata datastream from the previous version of the digital object.

Parameters:

  • dor_item (Dor::Item) —

    The DOR item being processed by the technical metadata robot

Returns:

  • (String) —

    The technicalMetadata datastream from the previous version of the digital object



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# File 'lib/dor/services/technical_metadata_service.rb', line 71

def self.get_old_technical_metadata(dor_item)
  sdr_techmd = get_sdr_technical_metadata(dor_item.pid)
  return sdr_techmd unless sdr_techmd.nil?
  get_dor_technical_metadata(dor_item)
end

.get_sdr_metadata(druid, dsname) ⇒ String

Returns The datastream contents from the previous version of the digital object (fetched from SDR storage).

Parameters:

  • druid (String) —

    The identifier of the digital object being processed by the technical metadata robot

  • dsname (String) —

    The identifier of the metadata datastream

Returns:

  • (String) —

    The datastream contents from the previous version of the digital object (fetched from SDR storage)



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# File 'lib/dor/services/technical_metadata_service.rb', line 102

def self.get_sdr_metadata(druid, dsname)
  Sdr::Client.get_sdr_metadata(druid, dsname)
end

.get_sdr_technical_metadata(druid) ⇒ String

Returns The technicalMetadata datastream from the previous version of the digital object (fetched from SDR storage) The data is updated to the latest format.

Parameters:

  • druid (String) —

    The identifier of the digital object being processed by the technical metadata robot

Returns:

  • (String) —

    The technicalMetadata datastream from the previous version of the digital object (fetched from SDR storage) The data is updated to the latest format.



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# File 'lib/dor/services/technical_metadata_service.rb', line 80

def self.get_sdr_technical_metadata(druid)
  sdr_techmd = get_sdr_metadata(druid, 'technicalMetadata')
  return sdr_techmd if sdr_techmd =~ /<technicalMetadata/
  return ::JhoveService.new.upgrade_technical_metadata(sdr_techmd) if sdr_techmd =~ /<jhove/
  nil
end

.merge_file_nodes(old_techmd, new_techmd, deltas) ⇒ Hash<String,Nokogiri::XML::Node>

Returns The complete set of technicalMetadata nodes for the digital object, indexed by filename.

Parameters:

  • old_techmd (String) —

    The technicalMetadata datastream from the previous version of the digital object

  • new_techmd (String) —

    The technicalMetadata datastream for the new files of the new digital object version

  • deltas (Array<String>) —

    The list of filenames for files that are either added or modifed since the previous version

Returns:

  • (Hash<String,Nokogiri::XML::Node>) —

    The complete set of technicalMetadata nodes for the digital object, indexed by filename



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# File 'lib/dor/services/technical_metadata_service.rb', line 135

def self.merge_file_nodes(old_techmd, new_techmd, deltas)
  old_file_nodes = get_file_nodes(old_techmd)
  new_file_nodes = get_file_nodes(new_techmd)
  merged_nodes = {}
  deltas[:identical].each do |path|
    merged_nodes[path] = old_file_nodes[path]
  end
  deltas[:modified].each do |path|
    merged_nodes[path] = new_file_nodes[path]
  end
  deltas[:added].each do |path|
    merged_nodes[path] = new_file_nodes[path]
  end
  deltas[:renamed].each do |oldpath, newpath|
    clone = old_file_nodes[oldpath].clone
    clone.sub!(/<file\s*id.*?["'].*?["'].*?>/, "<file id='#{newpath}'>")
    merged_nodes[newpath] = clone
  end
  deltas[:copyadded].each do |oldpath, newpath|
    clone = old_file_nodes[oldpath].clone
    clone.sub!(/<file\s*id.*?["'].*?["'].*?>/, "<file id='#{newpath}'>")
    merged_nodes[newpath] = clone
  end
  merged_nodes
end

.test_jhove_service ⇒ Boolean

Returns Make sure that the jhove-service gem is loaded.

Returns:

  • (Boolean) —

    Make sure that the jhove-service gem is loaded



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# File 'lib/dor/services/technical_metadata_service.rb', line 37

def self.test_jhove_service
  unless defined? ::JhoveService
    begin
      require 'jhove_service'
    rescue LoadError => e
      puts e.inspect
      raise 'jhove-service dependency gem was not found.  Please add it to your Gemfile and run bundle install'
    end
  end
end

.write_fileset(temp_dir, new_files) ⇒ Pathname

Returns Save the new_files list to a text file and return that file’s name.

Parameters:

  • temp_dir (Pathname) —

    The pathname of the temp folder in the object’s workspace area

  • new_files (Object) —
    Array<String>

    The list of filenames for files that are either added or modifed since the previous version

Returns:

  • (Pathname) —

    Save the new_files list to a text file and return that file’s name



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# File 'lib/dor/services/technical_metadata_service.rb', line 125

def self.write_fileset(temp_dir, new_files)
  fileset_pathname = Pathname(temp_dir).join('jhove_fileset.txt')
  fileset_pathname.open('w') {|f| f.puts(new_files) }
  fileset_pathname
end