module FileMutate
  module InsertContent
    def insert *args, &block
      File.insert_into self.path, *args, &block
    end

    module ClassMethods
      # insert_into 'my_file.txt', :after => 'Blip', :content => 'Hello
      # insert_into 'my_file.txt', 'Hello', :after => 'Blip' 
      # insert_into 'my_file.txt', :after => 'Blip' do 
      #  'Hello'
      # end  
      def insert_into file_name, *args, &block
        options = last_option args
        content = insertion_content options, *args, &block

        # no content to insert?
        return nil if content.blank? 

        file = begin
                 get_file(file_name)
               rescue
                 return nil
               end

        # already inserted?
        return nil if !options[:repeat] && file.has_content?(content)

        # find where to insert
        place, marker = if options[:before] 
                          [ :before, options[:before] ]
                        elsif options[:before_last]
                          [ :before_last, options[:before_last] ]
                        else
                          [ :after, options[:after] ]
                        end 

        return nil if !file.has_content?(marker)

        # do mutation
        res = file.mutate marker, place do
          content
        end
        res
      end

      def insertion_content options = {}, *args, &block
        case args.first
        when String
          args.first
        when Hash
          options[:content] || (yield if block)      
        else
          return yield if block
          raise ArgumentError, "You must supply content to insert, either as a String before the options hash, a :content option or a block" 
        end     
      end
    end
  end
end