Added backlink lookups.

README.md

@@ -1,7 +1,15 @@
-# page_rankr
+# PageRankr
 
 Provides an easy way to retrieve Google Page Rank, Alexa Rank, and backlink counts.
 
+## Exampes
+
+### Backlinks
+Backlinks are the result of doing a search with a query like "link:www.google.com". The number of returned results indicates how many sites point to that url.
+
+`PageRankr.backlinks 'www.google.com', :google, :bing, :yahoo, :altavista, :alltheweb`
+`    #=> {:google=>161000, :bing=>208000000, :yahoo=>256300062, :altavista=>110000000, :alltheweb=>55700000}`
+
 ## Note on Patches/Pull Requests
 
 * Fork the project.
@@ -13,12 +21,12 @@ Provides an easy way to retrieve Google Page Rank, Alexa Rank, and backlink coun
 * Send me a pull request. Bonus points for topic branches.
 
 ## TODO
-* Get backlink counts for:
-  * Google
-  * Bing
-  * Yahoo!
-  * AltaVista
-  * AllTheWeb
+* <strike>Get backlink counts for:</strike>
+  * <strike>Google</strike>
+  * <strike>Bing</strike>
+  * <strike>Yahoo!</strike>
+  * <strike>AltaVista</strike>
+  * <strike>AllTheWeb</strike>
 * Get Google Page Rank
   * Implement Hashing Algorithm
 * Get Alexa ranking

lib/page_rankr.rb

@@ -0,0 +1,13 @@
+path = File.expand_path(File.dirname(__FILE__))
+require 'open-uri'
+require 'cgi'
+require 'hpricot'
+require path + '/page_rankr/backlinks'
+
+module PageRankr
+  class << self
+    def backlinks(site, *search_engines)
+      Backlinks.lookup site, *search_engines
+    end
+  end
+end

lib/page_rankr/backlinks.rb

@@ -0,0 +1,29 @@
+class Backlinks
+  SEARCH_ENGINE_URLS = {
+    :google    => "http://www.google.com/search?q=link%3A",
+    :bing      => "http://www.bing.com/search?q=link%3A",
+    :yahoo     => "http://siteexplorer.search.yahoo.com/search?p=",
+    :altavista => "http://www.altavista.com/web/results?q=link%3A",
+    :alltheweb => "http://www.alltheweb.com/search?q=link%3A"
+  }
+
+  SEARCH_EGNINE_PATHS = {
+    :google    => "//p[@id='resultStats']/b[3]/text()",
+    :bing      => "//span[@class='sb_count']/text()",
+    :yahoo     => "//ol[@id='results-tab']/li[2]/a/text()",
+    :altavista => "//a[@class='lbl']/text()",
+    :alltheweb => "//span[@class='ofSoMany']/text()"
+  }
+
+  def self.lookup(site, *search_engines)
+    backlinks = {}
+    search_engines.each do |engine|
+      next unless SEARCH_ENGINE_URLS[engine]
+      doc = open(SEARCH_ENGINE_URLS[engine] + CGI.escape(site)) {|results| Hpricot(results)}
+      count = doc.at(SEARCH_EGNINE_PATHS[engine]).to_s
+      count = count.gsub('1-10', '').gsub(/[a-zA-Z,\s\(\)]/, '')
+      backlinks[engine] = count.to_i
+    end
+    backlinks
+  end
+end