#!/usr/bin/env ruby
  
  # This file is a part of an Information Retrieval oriented Ruby library
  #
  # Copyright (C) 2010-2011 Romain Deveaud <romain.deveaud@gmail.com>
  #
  # This program is free software: you can redistribute it and/or modify
  # it under the terms of the GNU General Public License as published by
  # the Free Software Foundation, either version 3 of the License, or
  # (at your option) any later version.
  #
  # This program is distributed in the hope that it will be useful,
  # but WITHOUT ANY WARRANTY; without even the implied warranty of
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  # GNU General Public License for more details.
  #
  # You should have received a copy of the GNU General Public License
  # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  
  # General module for many purposes related to Information Retrieval.

  module RIR

  
    # A Document is a bag of words and is constructed from a string.
    class Document
      attr_reader :words, :doc_content
  
      # Any non-word characters are removed from the words (see http://perldoc.perl.org/perlre.html
      # and the \\W special escape).
      # 
      # Protected function, only meant to by called at the initialization.                 
      def format_words
        wo = []
  
        @doc_content.split.each do |w|
          w.split(/\W/).each do |sw| 

            wo.push(sw.downcase) if sw =~ /[a-zA-Z]/ 

          end
        end
        
        wo
      end
  
      # Returns an Array containing the +n+-grams (words) from the current Document. 
      #
      #   ngrams(2) #=> ["the free", "free encyclopedia", "encyclopedia var", "var skin", ...]
      def ngrams(n)
        window       = []
        ngrams_array = []
  
        @words.each do |w|
          window.push(w)
          if window.size == n
            ngrams_array.push window.join(" ")
            window.delete_at(0)
          end
        end
  
        ngrams_array.uniq
      end
  
      # Returns a Hash containing the words and their associated counts in the current Document.
      #
      #   count_words #=> { "guitar"=>1, "bass"=>3, "album"=>20, ... } 
      def count_words
        counts = Hash.new { |h,k| h[k] = 0 }

        @words.each { |w| counts[w] += 1 }

  
        counts
      end
  
      # Computes the entropy of a given string +s+ inside the document.
      #
      # If the string parameter is composed of many words (i.e. tokens separated
      # by whitespace(s)), it is considered as an ngram.    
      #

      #   entropy("guitar") #=> 0.00432114812727959
      #   entropy("dillinger escape plan") #=> 0.265862076325102

      def entropy(s)
        en = 0.0
        counts = self.count_words
  
        s.split.each do |w|
          p_wi = counts[w].to_f/@words.count.to_f
          en += p_wi*Math.log2(p_wi)
        end
  
        en *= -1
        en
      end

      # Computes the term frequency of a given *word* +s+.
      #
      #   tf("guitar") #=> 0.000380372765310004
      def tf(s)
        self.count_words[s].to_f/@words.size.to_f
      end

  
  
      def initialize(content)
        @doc_content = content
        @words = format_words
      end
  
      protected :format_words
    end
  
    # A WebDocument is a Document with a +url+.
    class WebDocument < Document
      attr_reader :url
  
      # Returns the HTML text from the page of a given +url+.
      def self.get_content(url)
        require 'net/http'
        Net::HTTP.get(URI.parse(url))
      end
  
      # WebDocument constructor, the content of the Document is the HTML page
      # without the tags.
      def initialize(url)
        @url = url
        super WebDocument.get_content(url).strip_javascripts.strip_stylesheets.strip_xml_tags
      end
    end
  
    # A WikipediaPage is a WebDocument.
    class WikipediaPage < WebDocument

      require 'rexml/document'
      require 'net/http'
      require 'kconv'
  
  
      def self.search_wikipedia_titles(name)

        raise ArgumentError, "Bad encoding", name unless name.isutf8
  
        res = REXML::Document.new(Net::HTTP.get( URI.parse "http://en.wikipedia.org/w/api.php?action=query&list=search&srsearch=#{URI.escape name}&format=xml" ).toutf8).elements['api/query/search']

  
        res.collect { |e| e.attributes['title'] } unless res.nil?
      end
  
      def self.get_url(name)

        raise ArgumentError, "Bad encoding", name unless name.isutf8
  
        atts = REXML::Document.new(Net::HTTP.get( URI.parse "http://en.wikipedia.org/w/api.php?action=query&titles=#{URI.escape name}&inprop=url&prop=info&format=xml" ).toutf8).elements['api/query/pages/page'].attributes

  
        atts['fullurl'] if atts['missing'].nil?
      end
  
      def self.search_homepage(name)
        title = WikipediaPage.search_wikipedia_titles name

        WikipediaPage.new(WikipediaPage.get_url title[0]) unless title.nil? || title.empty?

      end
  
  #    def initialize(name)
  #      title = WikipediaPage.search_wikipedia_titles name
  #      raise ArgumentError, "No page found" if title.empty? 
  #      super WikipediaPage.get_url title[0]
  #    end

    end
  end