module Merb

  module ErubisCaptureMixin
    # Capture allows you to extract a part of the template into an 
    # instance variable. You can use this instance variable anywhere
    # in your templates and even in your layout. 
    # 
    # Example of capture being used in a .herb page:
    # 
    #   <% @foo = capture do %>
    #     <p>Some Foo content!</p> 
    #   <% end %>
    def capture(*args, &block)
      # execute the block
      begin
        buffer = eval("_buf", block.binding)
      rescue
        buffer = nil
      end
      
      if buffer.nil?
        capture_block(*args, &block)
      else
        capture_erb_with_buffer(buffer, *args, &block)
      end
    end
    
    # Calling throw_content stores the block of markup for later use.
    # Subsequently, you can make calls to it by name with <tt>catch_content</tt>
    # in another template or in the layout. 
    # 
    # Example:
    # 
    #   <% throw_content :header do %>
    #     alert('hello world')
    #   <% end %>
    #
    # You can use catch_content :header anywhere in your templates.
    #
    #   <%= catch_content :header %>
    def throw_content(name, content = nil, &block)
      eval "@_#{name}_content = (@_#{name}_content || '') + capture(&block)"
    end
    
    # catch_content catches the thrown content from another template
    # So when you throw_content(:foo) {...} you can catch_content :foo
    # in another view or the layout.
    def catch_content(name)
      instance_variable_get("@_#{name}_content")
    end
    
    private
      def capture_block(*args, &block)
        block.call(*args)
      end
    
      def capture_erb(*args, &block)
        buffer = eval("_buf", block.binding)
        capture_erb_with_buffer(buffer, *args, &block)
      end
    
      def capture_erb_with_buffer(buffer, *args, &block)
        pos = buffer.length
        block.call(*args)
      
        # extract the block 
        data = buffer[pos..-1]
      
        # replace it in the original with empty string
        buffer[pos..-1] = ''
      
        data
      end
    
      def erb_content_for(name, &block)
        eval "@_#{name}_content = (@_#{name}_content|| '') + capture_erb(&block)"
      end
    
      def block_content_for(name, &block)
        eval "@_#{name}_content = (@_#{name}_content|| '') + capture_block(&block)"
      end
  end
  
end