module Searchable
  def self.included(model)
    model.send(:extend, ClassMethods)
    model.class_eval do
      class_inheritable_accessor(:search_indexes)
      self.search_indexes = []
    end
  end

  module ClassMethods
    def search(query, options = {})
      conds = search_indexes.map{|idx| "#{idx}_search_index @@ plainto_tsquery(?)" }
      conds_array = [conds.join(" OR ")]
      search_indexes.size.times{ conds_array << escape_string(query) }
      all(options.merge(:conditions => conds_array))
    end

    private

    def escape_string(str)
      str.gsub(/([\0\n\r\032\'\"\\])/) do
        case $1
        when "\0" then "\\0"
        when "\n" then "\\n"
        when "\r" then "\\r"
        when "\032" then "\\Z"
        when "'"  then "''"
        else "\\"+$1
        end
      end
    end
  end
end