require 'MeCab'

module ActiveRecord
  module Acts
    module Mecabulltext
      def self.included(klass)
        klass.extend ClassMethods
      end

      module ClassMethods
        ALLOW_SEARCH_OPTIONS = [:conditions, :count, :order, :group, :limit, :offset, :include, :select, :readonly]

        def acts_as_mecabulltext(options = {})
          include ActiveRecord::Acts::Mecabulltext::PluginMethods

          cattr_accessor :fulltext_columns
          self.fulltext_columns = options[:fulltext_columns] || {}

          class_eval do
            before_create :update_fulltext_index
            before_update :update_fulltext_index
          end
        end

        def find_all_with_fulltext(query, options = {})
          options.reject{|opt,val|!ALLOW_SEARCH_OPTIONS.include? opt}

          with_scope(:find => {:conditions => options[:conditions]}) do
            options[:conditions] = [fulltext_condition, to_fulltext_query(query)]
            if options[:count]
              options.delete :count
              count(options)
            else
              find(:all, options)
            end
          end
        end

        def count_with_fulltext(query, options = {})
          find_all_with_fulltext(query, options.update({:count => true}))
        end

        def fulltext_condition
          columns   = self.fulltext_columns.values.map{|c|"#{table_name}.`#{c}`"}
          "MATCH(#{columns.join(',')}) AGAINST(? IN BOOLEAN MODE)"
        end

        def to_fulltext_index(content)
          mecab content
        end

        def to_fulltext_query(content)
          to_fulltext_index(content).split(' ').map{|chunk|"+#{chunk}"}.join(' ')
        end

        private
        def mecab(content)
          @@mecab ||= MeCab::Tagger.new('-Owakati')
          @@mecab.parse(content.delete("\r\n")).gsub(/^\s*|\s*$/, '')
        end
      end #ActiveRecord::Acts::Mecabulltext::ClassMethods

      module PluginMethods
        def update_fulltext_index
          return if self.class.fulltext_columns.empty?
          self.class.fulltext_columns.each do |field, index|
            __send__ "#{index}=", self.class.to_fulltext_index(__send__(field))
          end
        end
      end #ActiveRecord::Acts::Mecabulltext::PluginMethods
    end #ActiveRecord::Acts::Mecabulltext
  end # ActiveRecord::Acts
end # ActiveRecord

ActiveRecord::Base.send :include, ActiveRecord::Acts::Mecabulltext