require 'iconv'
require 'record_moved'

# Thanks to Mephisto for the iconv character translation code
# and kain for spotting the nested resources issues
# and thanks to Obie Fernandez for blogging about overiding #to_param

module ActiveRecord #:nodoc:
  module Acts #:nodoc:
    
    # Use this act if you want your models to use more descriptive :id fields in URLs
    # A model using acts_as_friendly_param may have a RESTful URL such as:
    #
    # /posts/4-the-day-the-earth-stood-still
    #
    module FriendlyParam
      
      # ClassMethods inheritance hack
      #
      def self.included(base) # :nodoc:
        base.extend ClassMethods
      end
      
      module ClassMethods
        
        # macro for enabling this act
        # by default friendly-param will try and use a
        # method called #name to find the name of the record
        # but you may specify another ie.
        #
        # acts_as_friendly_param :title
        # 
        # other options are for customising iconv charmap translation
        # methods ie.
        #
        # acts_as_friendly_param :name, :translation_to => 'utf-16'
        #
        # 
        def acts_as_friendly_param(name_method=:name, options={})
          # set translation methods
          #
          conv_to = options.fetch(:translation_to, "ascii//ignore//translit")
          conv_from = options.fetch(:translation_from, 'utf-8')
          #
          # construct the to_param method
          #  
          define_method :to_param do
            param = id.to_s
            if respond_to?(name_method) && name = send(name_method)
              s = Iconv.new(conv_to, conv_from).iconv(name)
              s = s.gsub(/[^-_\s\w]/, '').downcase.squeeze(' ').tr(' ','-')
              param << "-#{s}" unless s.blank?
            end
            param
          end
          #
          # since the URLs are to be based on the #name_method
          # it seems logical that the #name_method should be required and validated
          # against by default?
          # 
          # do something?
          
          # 
          # by default a RecordMoved error will be raised if the ID is matched
          # but the title text doesnt. to disable this feature use 
          # 
          # acts_as_friendly_param :name, :strict => false
          #
          if options.fetch(:strict, true)
            #
            # overide the default [internal] #find_one method to check that
            # the requested URL title matches the current model.
            # this is important for SEO, where ranking can be adversly affected
            # by multiple URLs pointing to the same content
            #
            class_eval do
              def self.find_one(id, options)
                record = super(id, options)
                #
                # check title text if the id is a string and more than
                # just a string version of an integer.
                #  
                if id.kind_of?(String) && (id != record.to_param)
                  raise RecordMoved.new(record), "A record with id=#{id.to_i.to_s} was found but '#{id.gsub(/^[0-9\-]+/,'')}' did not match"
                end
                record
              end
            end
          end
          #
        end 
               
      end #ClassMethods
      
    end #FriendlyParam
    
  end
end