Class: CoverThing

Inherits:
Service show all
Includes:
MetadataHelper
Defined in:
lib/service_adaptors/cover_thing.rb

Overview

Find book covers from LibraryThing’s CoverThing service. Only fetches “medium” size image. Fetches only by ISBN.

Constant Summary

Constants inherited from Service

Service::LinkOutFilterTask, Service::StandardTask

Instance Attribute Summary

Attributes inherited from Service

#name, #priority, #request, #service_id, #session_id, #status, #task, #url

Instance Method Summary collapse

Methods included from MetadataHelper

#get_doi, #get_gpo_item_nums, #get_identifier, #get_isbn, #get_issn, #get_lccn, #get_oclcnum, #get_pmid, #get_search_creator, #get_search_terms, #get_search_title, #get_sudoc, #get_top_level_creator, #get_year, #normalize_lccn, #normalize_title, #raw_search_title, #title_is_serial?

Methods included from MarcHelper

#add_856_links, #edition_statement, #get_title, #get_years, #gmd_values, #service_type_for_856, #should_skip_856_link?, #strip_gmd

Methods inherited from Service

#credits, #display_name, #handle_wrapper, #link_out_filter, #preempted_by, required_config_params, #response_to_view_data, #response_url, #view_data_from_service_type

Constructor Details

#initialize(config) ⇒ CoverThing

Returns a new instance of CoverThing.



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# File 'lib/service_adaptors/cover_thing.rb', line 13

def initialize(config)
  @display_name = "LibraryThing"
  # http://covers.librarything.com/devkey/KEY/medium/isbn/0545010225
  @base_url = 'http://covers.librarything.com/devkey/';
  @lt404url = 'http://www.librarything.com/coverthing404.php'
  
  @credits = {
    "LibraryThing" => "http://www.librarything.com/"
  }
  
  super(config)
end

Instance Method Details

#handle(request) ⇒ Object 



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# File 'lib/service_adaptors/cover_thing.rb', line 26

def handle(request)
  image_url = image_url(request.referent)
  return request.dispatched(self, true) unless image_url

  uri = URI.parse(image_url)
  response = nil
  # All we need is a HEAD request to check content-length. 
  Net::HTTP.start(uri.host, uri.port) {|http|
    response = http.head(uri.path)
  }
  
  # Only way to know if we got an image or a transparent placeholder
  # is to check the content-length. Currently the transparent placeholder
  # is 43 bytes. -- not true anymore, now we can check for a redirect,
  # I guess.

  # Not sure why response is ever nil, but sometimes it is, let's log
  # some info.
  if ( response.kind_of?(Net::HTTPRedirection) && response["location"] == @lt404url)
    # no cover found.
    return request.dispatched(self, true)
  elsif ( response.nil? || response.content_length.nil? )
    Rails.logger.debug("CoverThing: Null response for #{uri}, status #{response.class}")
  end
  unless (response.nil? || response.content_length.nil? || response.content_length < 50)
    request.add_service_response(
      :service=>self, 
      :display_text => 'Cover Image',
      :key=> 'medium', 
      :url => image_url, 
      :size => 'medium',
      :service_type_value => :cover_image
      )
  end

  return request.dispatched(self, true)    
end

#image_url(referent) ⇒ Object 



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# File 'lib/service_adaptors/cover_thing.rb', line 64

def image_url(referent)
  isbn = get_identifier(:urn, "isbn", referent)
  isbn.gsub!(/[^\d]/, '') if isbn # just numeric isbn
  return nil if isbn.blank? # need an isbn to make the request
  
  return @base_url + @developer_key + '/medium/isbn/' + isbn
end

#service_types_generated ⇒ Object 



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# File 'lib/service_adaptors/cover_thing.rb', line 9

def service_types_generated
  return [ ServiceTypeValue[:cover_image] ]       
end