require 'nano/inflect'

# The default Tag implementation. A tag attaches semantics to
# a given object.
#--
# FIXME: use index and char() instead of String.
#++

class Tag
  property :name, String, :uniq => true
  property :count, Fixnum
  
  # An alias for count.
  
  alias_method :freq, :count
  alias_method :frequency, :count  
  
  def initialize(name = nil)
    @name = name
    @count = 0
  end
  
  #--
  # FIXME: use update_properties here!
  #++
  
  def tag(obj)
    send(obj.class.name.underscore.pluralize.to_sym) << obj
    @count += 1
    save!
  end

  # Return all tagged objects from all categories.
  
  def tagged
    # TODO.  
  end
  
  # Helper method
  
  def self.total_frequency(tags = Tag.all)
    tags.inject(1) { |total, t| total += t.count }
  end
  
  def to_s
    @name
  end
end

module Glue

# Add tagging methods to the target class.
# For more information on the algorithms used surf:
# http://www.pui.ch/phred/archives/2005/04/tags-database-schemas.html
#
# === Example
#
# class Article
#    include Taggable
#    ..
#  end
#
# article.tag('navel', 'gmosx', 'nitro')
# article.tags
# article.tag_names
# Article.find_with_tags('navel', 'gmosx')
# Article.find_with_any_tag('name', 'gmosx')
#
# Tag.find_by_name('ruby').articles

module Taggable
  # The tag string separator.
  
  setting :separator, :default => ' ', :doc => 'The tag string separator'

  include Og::EntityMixin
  
  many_to_many Tag
  
  # Add a tag for this object.
  
  def tag(the_tags, options = {})
    options = {
      :clear => true
    }.merge(options)
      
    self.tags.clear if options[:clear]
    
    for name in Taggable.tags_to_names(the_tags)
      Tag.find_or_create_by_name(name).tag(self) unless self.tagged_with?(name)
    end    
  end
  alias_method :tag!, :tag  

  # Return the names of the tags.
  
  def tag_names
    tags.collect { |t| t.name }
  end

  # Return the tag string
  
  def tag_string(separator = Taggable.separator)
    tags.collect { |t| t.name }.join(separator)    
  end

  # Checks to see if this object has been tagged 
  # with +tag_name+.
  
  def tagged_with?(tag_name)
    tag_names.include?(tag_name)
  end
  alias_method :tagged_by?, :tagged_with?      

  module ClassMethods
    # Find objects with all of the provided tags.
    # INTERSECTION (AND)
  
    def find_with_tags(*names)
      info = ogmanager.store.join_table_info(self, Tag)
      count = names.size
      names = names.map { |n| "'#{n}'" }.join(',')
      sql = %{        
        SELECT o.* 
        FROM 
          #{info[:first_table]} AS o, 
          #{info[:second_table]} as t, 
          #{info[:table]} as j  
        WHERE o.oid = j.#{info[:first_key]} 
          AND t.oid = j.#{info[:second_key]} 
          AND (t.name in (#{names}))
        GROUP BY o.oid
        HAVING COUNT(o.oid) = #{count};
      }
      return self.select(sql)
    end
    alias_method :find_with_tag, :find_with_tags
  
    # Find objects with any of the provided tags.
    # UNION (OR)
  
    def find_with_any_tag(*names)
      info = ogmanager.store.join_table_info(self, Tag)
      count = names.size
      names = names.map { |n| "'#{n}'" }.join(',')
      sql = %{        
        SELECT o.* 
        FROM 
          #{info[:first_table]} AS o, 
          #{info[:second_table]} as t, 
          #{info[:table]} as j  
        WHERE 
          o.oid = j.#{info[:first_key]} 
          AND t.oid = j.#{info[:second_key]} 
          AND (t.name in (#{names}))
        GROUP BY o.oid
      }
      return self.select(sql)
    end
  end
  
  def self.included(base)
    Tag.module_eval do
      many_to_many base
    end
    base.extend(ClassMethods)
    #--
    # FIXME: Og should handle this automatically.
    #++
    base.send :include, Aspects
    base.before 'tags.clear', :on => [:og_delete]
  end
  
  # Helper.
  
  def self.tags_to_names(the_tags, separator = Taggable.separator)
    if the_tags.is_a? Array
      names = the_tags 
    elsif the_tags.is_a? String
      names = the_tags.split(separator)
    end
    
    names = names.flatten.uniq.compact
    
    return names
  end    
end

end

# * George Moschovitis <gm@navel.gr>