digger.rb

require 'index'

class Digger
  SEARCH_LIMIT = 19  
  
  def search(for_text)
    @search_params = for_text.words
    wrds = []
    @search_params.each { |param| wrds << "stem = '#{param}'" }
    word_sql = "select * from words where #{wrds.join(" or ")}"
    @search_words = repository(:default).adapter.query(word_sql)    
    tables, joins, ids = [], [], []
    @search_words.each_with_index { |w, index|
      tables << "locations loc#{index}"
      joins << "loc#{index}.page_id = loc#{index+1}.page_id"
      ids << "loc#{index}.word_id = #{w.id}"    
    }
    joins.pop        
    @common_select = "from #{tables.join(', ')} where #{(joins + ids).join(' and ')} group by loc0.page_id"    
    rank[0..SEARCH_LIMIT]
  end

  def rank
    merge_rankings(frequency_ranking, location_ranking, distance_ranking)
  end
    
  def frequency_ranking
    freq_sql= "select loc0.page_id, count(loc0.page_id) as count #{@common_select} order by count desc"
    list = repository(:default).adapter.query(freq_sql)
    rank = {}
    list.size.times { |i| rank[list[i].page_id] = list[i].count.to_f/list[0].count.to_f }  
    return rank
  end  
  
  def location_ranking
    total = []
    @search_words.each_with_index { |w, index| total << "loc#{index}.position + 1" }
    loc_sql = "select loc0.page_id, (#{total.join(' + ')}) as total #{@common_select} order by total asc" 
    list = repository(:default).adapter.query(loc_sql) 
    rank = {}
    list.size.times { |i| rank[list[i].page_id] = list[0].total.to_f/list[i].total.to_f }
    return rank
  end
  
  def distance_ranking
    return {} if @search_words.size == 1
    dist, total = [], []
    @search_words.each_with_index { |w, index| total << "loc#{index}.position" }    
    total.size.times { |index| dist << "abs(#{total[index]} - #{total[index + 1]})" unless index == total.size - 1 }    
    dist_sql = "select loc0.page_id, (#{dist.join(' + ')}) as dist #{@common_select} order by dist asc"  
    list = repository(:default).adapter.query(dist_sql) 
    rank = Hash.new
    list.size.times { |i| rank[list[i].page_id] = list[0].dist.to_f/list[i].dist.to_f }
    return rank
  end
  
  def merge_rankings(*rankings)
    r = {}
    rankings.each { |ranking| r.merge!(ranking) { |key, oldval, newval| oldval + newval} }
    r.sort {|a,b| b[1]<=>a[1]}    
  end
end