Get apps and their attributes from Google Play.

play.rb

require 'net/https'
require 'nokogiri'
require 'uri'

module Play
  STORE_IDENTIFIER_PATTERN = /(?:[\w\d]+\.)+[\w\d]+/i
  class InvalidStoreId < StandardError; end

  class Reader 
    def self.document_from_url(url)
      uri = URI.parse(url) 
      http = Net::HTTP.new(uri.host, uri.port)
      http.use_ssl = true
      http.verify_mode = OpenSSL::SSL::VERIFY_NONE

      request = Net::HTTP::Get.new(uri.request_uri)

      response = http.request(request)
      Nokogiri::HTML(response.body) if response.kind_of? Net::HTTPOK
    end
  end
  
  class App
    URL_TEMPLATE = "https://play.google.com/store/apps/details?id=<identifier>"

    def initialize(options={}) 
      raise StandardError if options[:document].nil? 
      @content = options[:document].at_css('div.page-content')
      #Local cache of DOM nodes to allow for lazy loading
      @cached = {}
    end    
   
    def title
      @title ||= title_container.at_css('h1.doc-banner-title').content.to_s
    end

    def developer
      @developer ||= title_container.at_css('a.doc-header-link').content.to_s
    end

    def description
      #TODO
    end

    def updated
      @updated ||= metadata_container.at_css('dd > time[itemprop="datePublished"]').content.to_s
    end

    def rating
      @rating ||= rating_container.at_css('div.ratings').attribute('content').content.to_f
    end

    def votes
      @votes ||= rating_container.at_css('span[itemprop="ratingCount"]').attribute('content').content.to_i
    end

    def size
      @size ||= metadata_container.at_css('dd[itemprop="fileSize"]').content.to_s
    end

    def price
      @prize ||= metadata_container.at_css('dd[itemprop="offers"] > span[itemprop="price"]').attribute('content').content.to_f
    end

    def content_rating
      #TODO
    end

    def self.search(identifier)
      raise InvalidStoreId unless identifier =~ Play::STORE_IDENTIFIER_PATTERN
      url = self.app_url(identifier)
      document = Play::Reader.document_from_url(url)
      App.new({:document => document})
    end

    def self.app_url(identifier)
      URL_TEMPLATE.gsub(/<identifier>/, identifier)
    end

    private
    def title_container
      @cached[:title_container] ||= @content.at_css('table.layout-table > tr > td > div > div.doc-banner-container > table.doc-banner-table > tr > td.doc-banner-title-container')
    end
   
    def details_container 
      @cached[:details_container] ||= @content.at_css('table.layout-table > tr > td.content-cell > div.doc-overview-tab')
    end

    def metadata_container
      @cached[:metadata_container] ||= details_container.at_css('div.doc-metadata > dl.doc-metadata-list')
    end

    def rating_container
      @cached[:ratings_container] ||= metadata_container.at_css('dd[itemprop="aggregateRating"]')
    end
  end
end

spec.rb

describe Play::App do
  describe ".search" do
    context "with invalid store identifier" do
      it "should throw exception" do
        expect {Play::App.search("com") }.to raise_error(Play::InvalidStoreId)
      end
    end
  
    context "with valid store identifier" do
      subject do
        identifier = "com.tapjoy.tapdefense"
        app = Play::App.search(identifier)
      end
      
      it { should be_an_instance_of(Play::App) }
      its(:title) { should eq "TapDefense" }
      its(:size) { should eq "6.1M" }
      its(:developer) { should eq "Tapjoy" }
      its(:updated) { should eq "December 5, 2012" }
      its(:rating) { should eq 3.5 } 
      its(:votes) { should eq 3455 }
      its(:price) { should eq 0 }
    end
  end
end