Class: BbEPUB::Transform::PackageIdentifier

Inherits:
Bookbinder::Transform
  • Object
show all
Defined in:
lib/bb-epub/transform/package_identifier.rb

Overview

See: www.idpf.org/epub/30/spec/epub30-publications.html#sec-opf-metadata-identifiers-pid

“To redress this problem of identifying minor modifications and releases without changing the Unique Identifier, this specification defines the semantics for a Package Identifier, or means of distinguishing and sequentially ordering Publications with the same Unique Identifier. The Package Identifier is not an actual property in the package metadata section, but is a value that can be obtained from two required pieces of metadata: the Unique Identifier and the last modification date of the Publication.

“When the taken together, the combined value represents a unique identity that can be used to distinguish any particular version of an EPUB Manifestation from another. To ensure that a Package Identifier can be constructed, the Publication must include exactly one ‘modified` property containing the last modification date (see meta).”

Instance Method Summary collapse

Instance Method Details

#dependencies ⇒ Object 



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# File 'lib/bb-epub/transform/package_identifier.rb', line 19

def dependencies
  [BbEPUB::Transform::Metadata, BbEPUB::Transform::NCX]
end

#from_map(package) ⇒ Object 



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# File 'lib/bb-epub/transform/package_identifier.rb', line 58

def from_map(package)
  map_uid = package.map['unique-identifier']
  map_mod = package.map['modified']
  opf_doc = package.file(:opf).document
  metadata_tag = opf_doc.find('opf|metadata')

  # Unique identifier
  opf_doc.root['unique-identifier'] = 'unique-identifier'
  opf_doc.new_node('dc:identifier', :append => metadata_tag) { |uid_tag|
    uid_tag['id'] = 'unique-identifier'
    uid_tag.content = map_uid
  }

  # Add the unique identifier to the NCX as well, because too
  # much data redundancy is never enough.
  package.if_file(:ncx) { |ncx_file|
    ncx_file.document.new_node('meta', :append => 'ncx|head') { |uid_meta_tag|
      uid_meta_tag['name'] = 'dtb:uid'
      uid_meta_tag['content'] = map_uid
    }
  }

  # Modified
  opf_doc.new_node('meta', :append => metadata_tag) { |mod_tag|
    mod_tag['property'] = 'dcterms:modified'
    mod_tag.content = map_mod
  }
end

#to_map(package) ⇒ Object 



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# File 'lib/bb-epub/transform/package_identifier.rb', line 24

def to_map(package)
  opf_doc = package.file(:opf).document('r')

  # Unique identifier
  unless id_hashes = package.map['metadata']['identifier']
    package.warn('No identifiers found in package metadata')
  end
  if id_hashes && uid_id = opf_doc.root['unique-identifier']
    uid_hash = id_hashes.detect { |id_hash|
      id_hash['id'] && id_hash['id']['@'] == uid_id
    }
  else
    package.warn('OPF root "unique-identifier" attribute not found')
  end
  if uid_hash
    id_hashes.delete(uid_hash)
    package.map['metadata'].delete('identifier')  if id_hashes.empty?
    package.map['unique-identifier'] = uid_hash['@']
  else
    package.warn('OPF metadata for required "unique-identifier" not found')
  end

  # Modified
  begin
    mod_hash = package.map['metadata'].delete('dcterms:modified').first
    timestamp = Time.parse(mod_hash['@'])
  rescue
    package.warn('OPF metadata for "modified" not found - using now()')
    timestamp = Time.now
  end
  package.map['modified'] = timestamp.utc.iso8601
end