Class: Stanford::ContentInventory

Inherits:
Object
  • Object
show all
Defined in:
lib/stanford/content_inventory.rb

Overview

Note:

Copyright © 2012 by The Board of Trustees of the Leland Stanford Junior University. All rights reserved. See LICENSE for details.

Stanford-specific utility methods for transforming contentMetadata to versionInventory and doing comparisons

Data Model

  • DorMetadata = utility methods for interfacing with Stanford metadata files (esp contentMetadata)

    • ContentInventory [1..1] = utilities for transforming contentMetadata to versionInventory and doing comparisons

    • ActiveFedoraObject [1..*] = utility for extracting content or other information from a Fedora Instance

Instance Method Summary collapse

Instance Method Details

#generate_content_metadata(file_group, object_id, version_id) ⇒ String

Returns The contentMetadata instance generated from the FileGroup.

Examples:

Parameters:

  • file_group (FileGroup) —

    The FileGroup object used as the data source

Returns:

  • (String) —

    The contentMetadata instance generated from the FileGroup



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# File 'lib/stanford/content_inventory.rb', line 97

def generate_content_metadata(file_group, object_id, version_id)
  cm = Nokogiri::XML::Builder.new do |xml|
    xml.contentMetadata(:type => "sample", :objectId => object_id) do
      xml.resource(:type => "version", :sequence => "1", :id => "version-#{version_id}") do
        file_group.files.each do |file_manifestation|
          signature = file_manifestation.signature
          file_manifestation.instances.each do |instance|
            xml.file(
              :id => instance.path,
              :size => signature.size,
              :datetime => instance.datetime,
              :shelve => 'yes',
              :publish => 'yes',
              :preserve => 'yes'
            ) do
              fixity = signature.fixity
              xml.checksum(:type => "MD5") { xml.text signature.md5 } if fixity[:md5]
              xml.checksum(:type => "SHA-1") { xml.text signature.sha1 } if fixity[:sha1]
              xml.checksum(:type => "SHA-256") { xml.text signature.sha256 } if fixity[:sha256]
            end
          end
        end
      end
    end
  end
  cm.to_xml
end

#generate_instance(node) ⇒ FileInstance

Returns The FileInstance object generated from the XML data.

Parameters:

  • node (Nokogiri::XML::Node) —

    The XML node containing file information

Returns:

  • (FileInstance) —

    The FileInstance object generated from the XML data



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# File 'lib/stanford/content_inventory.rb', line 82

def generate_instance(node)
  instance = Moab::FileInstance.new
  instance.path = node.attributes['id'].content
  instance.datetime = begin
                        node.attributes['datetime'].content
                      rescue
                        nil
                      end
  instance
end

#generate_signature(node) ⇒ FileSignature

Returns The FileSignature object generated from the XML data.

Parameters:

  • node (Nokogiri::XML::Node) —

    The XML node containing file information

Returns:

  • (FileSignature) —

    The FileSignature object generated from the XML data



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# File 'lib/stanford/content_inventory.rb', line 62

def generate_signature(node)
  signature = Moab::FileSignature.new
  signature.size = node.attributes['size'].content
  checksum_nodes = node.xpath('checksum')
  checksum_nodes.each do |checksum_node|
    case checksum_node.attributes['type'].content.upcase
    when 'MD5'
      signature.md5 = checksum_node.text
    when 'SHA1', 'SHA-1'
      signature.sha1 = checksum_node.text
    when 'SHA256', 'SHA-256'
      signature.sha256 = checksum_node.text
    end
  end
  signature
end

#group_from_cm(content_metadata, subset) ⇒ FileGroup

Returns The FileGroup object generated from a contentMetadata instance.

Examples:

Parameters:

  • content_metadata (String) —

    The contentMetadata as a string

  • subset (String) —

    Speciifes which subset of files to list (all|preserve|publish|shelve)

Returns:

  • (FileGroup) —

    The FileGroup object generated from a contentMetadata instance



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# File 'lib/stanford/content_inventory.rb', line 35

def group_from_cm(content_metadata, subset)
  ng_doc = Nokogiri::XML(content_metadata)
  validate_content_metadata(ng_doc)
  nodeset = case subset.to_s.downcase
            when 'preserve'
              ng_doc.xpath("//file[@preserve='yes']")
            when 'publish'
              ng_doc.xpath("//file[@publish='yes']")
            when 'shelve'
              ng_doc.xpath("//file[@shelve='yes']")
            when 'all'
              ng_doc.xpath("//file")
            else
              raise "Unknown disposition subset (#{subset})"
            end
  content_group = Moab::FileGroup.new(:group_id => 'content', :data_source => "contentMetadata-#{subset}")
  nodeset.each do |file_node|
    signature = generate_signature(file_node)
    instance = generate_instance(file_node)
    content_group.add_file_instance(signature, instance)
  end
  content_group
end

#inventory_from_cm(content_metadata, object_id, subset, version_id = nil) ⇒ FileInventory

Returns The versionInventory equivalent of the contentMetadata if the supplied content_metadata is blank or empty, then a skeletal FileInventory will be returned.

Parameters:

  • content_metadata (String) —

    The content metadata to be transformed into a versionInventory

  • object_id (String) —

    The identifier of the digital object

  • subset (String) —

    Speciifes which subset of files to list (all|preserve|publish|shelve)

  • version_id (Integer) (defaults to: nil) —

    The ID of the version whosen content metadata is to be transformed

Returns:

  • (FileInventory) —

    The versionInventory equivalent of the contentMetadata if the supplied content_metadata is blank or empty, then a skeletal FileInventory will be returned



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# File 'lib/stanford/content_inventory.rb', line 18

def inventory_from_cm(content_metadata, object_id, subset, version_id = nil)
  # The contentMetadata datastream is not required for ingest, since some object types, such as collection
  #   or APO do not require one.
  # Many of these objects have contentMetadata with no child elements, such as this:
  #    <contentMetadata objectId="bd608mj3166" type="file"/>
  # but there are also objects that have no datasteam of this name at all
  cm_inventory = Moab::FileInventory.new(:type => "version", :digital_object_id => object_id, :version_id => version_id)
  content_group = group_from_cm(content_metadata, subset)
  cm_inventory.groups << content_group
  cm_inventory
end

#remediate_checksum_nodes(file_node, signature) ⇒ void

This method returns an undefined value.

Returns update the file’s checksum elements if data missing, raise exception if inconsistent.

Parameters:

  • file_node (Nokogiri::XML::Element) —

    the File stanza being remediated

  • signature (FileSignature) —

    the fixity data for the file from the FileGroup



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# File 'lib/stanford/content_inventory.rb', line 208

def remediate_checksum_nodes(file_node, signature)
  # collect <checksum> elements for checksum types that are already present
  checksum_nodes = {}
  file_node.xpath('checksum').each do |checksum_node|
    type = @type_for_name[checksum_node['type']]
    checksum_nodes[type] = checksum_node
  end
  # add new <checksum> elements for the other checksum types that were missing
  @names_for_type.each do |type, names|
    unless checksum_nodes.key?(type)
      checksum_node = Nokogiri::XML::Element.new('checksum', file_node.document)
      checksum_node['type'] = names[0]
      file_node << checksum_node
      checksum_nodes[type] = checksum_node
    end
  end
  # make sure the <checksum> element has a content value
  checksum_nodes.each do |type, checksum_node|
    cm_checksum = checksum_node.content
    sig_checksum = signature.checksums[type]
    if cm_checksum.nil? || cm_checksum.empty?
      checksum_node.content = sig_checksum
    elsif cm_checksum != sig_checksum
      raise "Inconsistent #{type} for #{file_node['id']}: #{cm_checksum} != #{sig_checksum}"
    end
  end
end

#remediate_content_metadata(content_metadata, content_group) ⇒ String

Returns a remediated copy of the contentMetadata with fixity data filled in

Parameters:

  • content_metadata (String) —

    The contentMetadata as a string

  • content_group (FileGroup) —

    The FileGroup object used as the fixity data source

Returns:

  • (String) —

    Returns a remediated copy of the contentMetadata with fixity data filled in

See Also:



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# File 'lib/stanford/content_inventory.rb', line 176

def remediate_content_metadata(content_metadata, content_group)
  return nil if content_metadata.nil?
  return content_metadata if content_group.nil? || content_group.files.empty?
  signature_for_path = content_group.path_hash
  @type_for_name = Moab::FileSignature.checksum_type_for_name
  @names_for_type = Moab::FileSignature.checksum_names_for_type
  ng_doc = Nokogiri::XML(content_metadata, &:noblanks)
  nodeset = ng_doc.xpath("//file")
  nodeset.each do |file_node|
    filepath = file_node['id']
    signature = signature_for_path[filepath]
    remediate_file_size(file_node, signature)
    remediate_checksum_nodes(file_node, signature)
  end
  ng_doc.to_xml(:indent => 2)
end

#remediate_file_size(file_node, signature) ⇒ void

This method returns an undefined value.

Returns update the file size attribute if missing, raise exception if inconsistent.

Parameters:

  • file_node (Nokogiri::XML::Element) —

    the File stanza being remediated

  • signature (FileSignature) —

    the fixity data for the file from the FileGroup



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# File 'lib/stanford/content_inventory.rb', line 196

def remediate_file_size(file_node, signature)
  file_size = file_node['size']
  if file_size.nil? || file_size.empty?
    file_node['size'] = signature.size.to_s
  elsif file_size != signature.size.to_s
    raise "Inconsistent size for #{file_node['id']}: #{file_size} != #{signature.size}"
  end
end

#validate_content_metadata(content_metadata) ⇒ Boolean

Returns True if contentMetadata has essential file attributes, else raise exception.

Parameters:

  • content_metadata (String, Nokogiri::XML::Document) —

    The contentMetadata as a string or XML doc

Returns:

  • (Boolean) —

    True if contentMetadata has essential file attributes, else raise exception

Raises:



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# File 'lib/stanford/content_inventory.rb', line 127

def validate_content_metadata(content_metadata)
  result = validate_content_metadata_details(content_metadata)
  raise Moab::InvalidMetadataException, result[0] + " ..." unless result.empty?
  true
end

#validate_content_metadata_details(content_metadata) ⇒ Array<String>

Returns List of problems found.

Parameters:

  • content_metadata (String, Nokogiri::XML::Document) —

    The contentMetadata as a string or XML doc

Returns:

  • (Array<String>) —

    List of problems found



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# File 'lib/stanford/content_inventory.rb', line 135

def validate_content_metadata_details(content_metadata)
  result = []
  content_metadata_doc =
    case content_metadata.class.name
    when "String"
      Nokogiri::XML(content_metadata)
    when "Pathname"
      Nokogiri::XML(content_metadata.read)
    when "Nokogiri::XML::Document"
      content_metadata
    else
      raise Moab::InvalidMetadataException, "Content Metadata is in unrecognized format"
    end
  nodeset = content_metadata_doc.xpath("//file")
  nodeset.each do |file_node|
    missing = %w[id size md5 sha1]
    missing.delete('id') if file_node.has_attribute?('id')
    missing.delete('size') if file_node.has_attribute?('size')
    checksum_nodes = file_node.xpath('checksum')
    checksum_nodes.each do |checksum_node|
      case checksum_node.attributes['type'].content.upcase
      when 'MD5'
        missing.delete('md5')
      when 'SHA1', 'SHA-1'
        missing.delete('sha1')
      end
    end
    if missing.include?('id')
      result << "File node #{nodeset.index(file_node)} is missing #{missing.join(',')}"
    elsif !missing.empty?
      id = file_node['id']
      result << "File node having id='#{id}' is missing #{missing.join(',')}"
    end
  end
  result
end