module SinatraMore
  module OutputHelpers
    # Captures the html from a block of template code for erb or haml
    # capture_html(&block) => "...html..."
    def capture_html(*args, &block)
      if self.respond_to?(:is_haml?) && is_haml?
        block_is_haml?(block) ? capture_haml(*args, &block) : block.call
      elsif has_erb_buffer?
        result_text = capture_erb(*args, &block)
        result_text.present? ? result_text : (block_given? && block.call(*args))
      else # theres no template to capture, invoke the block directly
        block.call(*args)
      end
    end

    # Outputs the given text to the templates buffer directly
    # concat_content("This will be output to the template buffer in erb or haml")
    def concat_content(text="")
      if self.respond_to?(:is_haml?) && is_haml?
        haml_concat(text)
      elsif has_erb_buffer?
        erb_concat(text)
      else # theres no template to concat, return the text directly
        text
      end
    end

    # Returns true if the block is from an ERB or HAML template; false otherwise.
    # Used to determine if html should be returned or concatted to view
    # block_is_template?(block)
    def block_is_template?(block)
      block && (block_is_erb?(block) || (self.respond_to?(:block_is_haml?) && block_is_haml?(block)))
    end

    # Capture a block of content to be rendered at a later time.
    # Your blocks can also receive values, which are passed to them by <tt>yield_content</tt>
    # content_for(:name) { ...content... }
    # content_for(:name) { |name| ...content... }
    def content_for(key, &block)
      content_blocks[key.to_sym] << block
    end

    # Render the captured content blocks for a given key.
    # You can also pass values to the content blocks by passing them
    # as arguments after the key.
    # yield_content :include
    # yield_content :head, "param1", "param2"
    def yield_content(key, *args)
      blocks = content_blocks[key.to_sym]
      return nil if blocks.empty?
      blocks.map { |content|
        capture_html(*args, &content)
      }.join
    end

    protected

    # Retrieves content_blocks stored by content_for or within yield_content
    # content_blocks[:name] => ['...', '...']
    def content_blocks
      @content_blocks ||= Hash.new {|h,k| h[k] = [] }
    end

    # Used to capture the html from a block of erb code
    # capture_erb(&block) => '...html...'
    def capture_erb(*args, &block)
      erb_with_output_buffer { block_given? && block.call(*args) }
    end

    # Concats directly to an erb template
    # erb_concat("Direct to buffer")
    def erb_concat(text)
      @_out_buf << text if has_erb_buffer?
    end

    # Returns true if an erb buffer is detected
    # has_erb_buffer? => true
    def has_erb_buffer?
      !@_out_buf.nil?
    end

    # Used to determine if a block is called from ERB.
    # NOTE: This doesn't actually work yet because the variable __in_erb_template
    # hasn't been defined in ERB. We need to find a way to fix this.
    def block_is_erb?(block)
      has_erb_buffer? || block && eval('defined? __in_erb_template', block)
    end

    # Used to direct the buffer for the erb capture
    def erb_with_output_buffer(buf = '') #:nodoc:
      @_out_buf, old_buffer = buf, @_out_buf
      yield
      @_out_buf
    ensure
      @_out_buf = old_buffer
    end
  end
end
