book_search.rb

require "rubygems"
require "httparty"
require "isbn"

module Book; end unless defined? Book
module Book::Search
  include HTTParty
  base_uri "books.google.com"; format :xml

  class << self

    attr_reader :asin, :book

    def [](asin)
      @asin = asin
      feed = get("/books/feeds/volumes", :query => { :q => "isbn:#{asin}" })["feed"]
      @book = feed ? feed["entry"] : nil
      return @book ? self : nil
    end

    def extract(field)
      entry = book.is_a?(Array) ? book[0]["dc:#{field}"] : book["dc:#{field}"]
      return entry.is_a?(Array) ? entry[0] : entry
    rescue
      ""
    end

    def method_missing(method)
      extract(method)
    end

    def copyright
      date.to_i
    end

    def author
      creator
    end

    def isbn
      ISBN.thirteen(asin)
    end
  end
end

if __FILE__ == $0
  require 'test/unit'

  class BookSearchTest < Test::Unit::TestCase
    def setup
      @book = Book::Search["0674880145"]
    end

    def test_isbn
      assert_equal "9780674880146", @book.isbn
    end

    def test_author
      assert_equal "John Rawls", @book.author
    end

    def test_title
      assert_equal "A Theory of Justice", @book.title
    end

    def test_publisher
      assert_equal "Harvard Univ Pr", @book.publisher
    end

    def test_copyright
      assert_equal 1971, @book.copyright
    end
  end
end