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require 'active_support/core_ext/array/wrap'

class Hash
  private
    # Returns a JSON string representing the hash.
    #
    # Without any +options+, the returned JSON string will include all
    # the hash keys. For example:
    #
    #   { :name => "Konata Izumi", 'age' => 16, 1 => 2 }.to_json
    #   # => {"name": "Konata Izumi", "1": 2, "age": 16}
    #
    # The keys in the JSON string are unordered due to the nature of hashes.
    #
    # The <tt>:only</tt> and <tt>:except</tt> options can be used to limit the
    # attributes included, and will accept 1 or more hash keys to include/exclude.
    #
    #   { :name => "Konata Izumi", 'age' => 16, 1 => 2 }.to_json(:only => [:name, 'age'])
    #   # => {"name": "Konata Izumi", "age": 16}
    #
    #   { :name => "Konata Izumi", 'age' => 16, 1 => 2 }.to_json(:except => 1)
    #   # => {"name": "Konata Izumi", "age": 16}
    #
    # The +options+ also filter down to any hash values. This is particularly
    # useful for converting hashes containing ActiveRecord objects or any object
    # that responds to options in their <tt>to_json</tt> method. For example:
    #
    #   users = User.find(:all)
    #   { :users => users, :count => users.size }.to_json(:include => :posts)
    #
    # would pass the <tt>:include => :posts</tt> option to <tt>users</tt>,
    # allowing the posts association in the User model to be converted to JSON
    # as well.
    def rails_to_json(options = nil, *args) #:nodoc:
      hash_keys = self.keys

      if options
        if except = options[:except]
          hash_keys = hash_keys - Array.wrap(except)
        elsif only = options[:only]
          hash_keys = hash_keys & Array.wrap(only)
        end
      end

      result = '{'
      result << hash_keys.map do |key|
        "#{ActiveSupport::JSON.encode(key.to_s)}:#{ActiveSupport::JSON.encode(self[key], options, *args)}"
      end * ','
      result << '}'
    end
end