require 'cgi'

module Jangle
  
  # This filter adds querystring variables to a request. If they are in the querystring
  # already, they are overwritten if @overwrite is set to true; otherwise
  # the original value is retained.
  class QuerystringAddingFilter
    attr_accessor :fields_to_add, :overwrite
    
    def initialize(fields_to_add={}, overwrite=false)
      @fields_to_add = fields_to_add
      @overwrite = overwrite
    end
      
    def filter(rack_request)
      LOGGER.debug "Original querystring before filtering: " + rack_request.query_string
      
      querystring_vars = rack_request.GET
      if @overwrite
        querystring_vars.merge!(@fields_to_add) { |_, _, new_val| new_val }
      else
        querystring_vars.merge!(@fields_to_add) { |_, old_val, _| old_val }
      end
      
      new_querystring = []
      querystring_vars.each do |key, value|
        new_querystring.push("#{key}=" + CGI.escape(value))
      end
      
      rack_request.env["rack.request.query_hash"] = querystring_vars
      rack_request.env["QUERY_STRING"] = new_querystring.join('&')
      
      LOGGER.debug "Querystring after filtering: " + rack_request.query_string
    end
    
  end
end