module ActionView
  module Helpers
    module JavaScriptMacrosHelper

      # Adds LOCAL autocomplete functionality to the text input field with the DOM ID specified by +field_id+.
      # This DOES NOT query the server via AJAX - it returns results from a pre-fetched javascript array.
      #
      # <tt>field_id</tt>:: The text field to auto-complete. 
      # <tt>items</t>::     An array of objects that will be turned into a javascript array. These items will be 
      #                     mapped to an array of strings by calling item#field_id on each array item. To override,
      #                     specify the accessor method with the +:method+ option.
      #
      #                     Example: 
      #
      #                     <%= local_auto_complete_field('name',@labels) %> => @labels.map { |label| label.name }
      #                     <%= local_auto_complete_field('name',@labels, :method => 'description') %> => @labels.map { |label| label.description }
      #
      # +options+ are:
      #
      # <tt>:auto_complete_results_id</tt> :: The element id of the DOM element containing the auto-complete results. 
      # <tt>:method</tt> :: The method to call on +items+ to turn the array of +items+ into an array of strings.
      #
      # In addtion, options specific to the javascript functionality can be specified in +completion_options+. 
      def local_auto_complete_field(field_id, items, options = {}, completion_options = {})
        options = {:auto_complete_results_id => "#{field_id}_auto_complete",
                   :method => field_id}.merge(options)
  
        completion_options = {:fullSearch => true,
                              :frequency => 0,
                              :minChars => 1,
                              :skip_style => false}.merge(completion_options)
  
        html = (completion_options[:skip_style] ? "" : auto_complete_stylesheet)
        html << "<div class=\"auto_complete\" id=\"#{options[:auto_complete_results_id]}\"></div>"
        html << javascript_tag("new Autocompleter.Local( '#{field_id}' , '#{options[:auto_complete_results_id]}', 
                               #{ generate_javascript_array(items,options[:method])},
        											 #{completion_options.to_json}
        											);")
        return html
      end
      
      private

      # Called by +#local_auto_complete_field+ to turn +items+ into a javascript array of strings. 
      def generate_javascript_array(items,method)
        "[#{items.map { |item| item.send(method).gsub(/\A|\Z/, "'")  }.join(',')}]"
      end

    end
  end
end