query.rb

class Query
  include Frequency
  attr_accessor :freq

  def initialize(query)
    @query  = query
    @tokens = tokenize
  end

  def clean_text
    @query
  end

  def ids
    @ids ||= @tokens.reduce(Message.corpus.index @tokens.first) do |memo, it|
      memo & Message.corpus.index(it)
    end.flatten.uniq
  end

  def docs(page)
    mailings = Mailing.limited.paginate(:page => page, :per_page => 10).includes(:campaign).order('first_seen DESC').where('id in (?)', ids)

    docs = Message.doc_length

    scores = mailings.map do |m|
      max_word = keys.map {|k| freq[k] }.max

      score = @tokens.reduce(0.0) do |memo, tok|
        memo += (m.freq[tok] / max_word) * Math.log(docs / (1.0 + Message.corpus.docs(tok))) if !m.freq[tok].nil?
        memo
      end
      {:score => score, :mailing => m}
    end

    scores.sort_by {|s|
      (s[:score] / (s[:mailing].keys.length * s[:mailing].freq.values.reduce(&:+))) * -1.0
    }.map {|s| s[:mailing] }
  end
end