module Slideshow
  module SlideFilter

# add slide directive before h1 (tells slideshow gem where to break slides)
#
# e.g. changes:
# <h1 id='optional' class='optional'>
#  to
# <!-- _S9SLIDE_ -->
# <h1 id='optional' class='optional'>

def add_slide_directive_before_h1( content )

  # mark h1 for getting wrapped into slide divs
  # note: use just <h1 since some processors add ids e.g. <h1 id='x'>

  slide_count = 0

  content.gsub!( /<h1/ ) do |match|
    slide_count += 1
    "\n<!-- _S9SLIDE_ -->\n#{Regexp.last_match(0)}"
  end
  
  puts "  Adding #{slide_count} slide breaks (using h1 rule)..."
  
  content
end

# add slide directive before div h1 (for pandoc-generated html)
#
# e.g. changes:
# <div id='header'>
# <h1 id='optional' class='optional'>
#  to
# <!-- _S9SLIDE_ -->
# <div id='header'>
# <h1 id='optional' class='optional'>


def add_slide_directive_before_div_h1( content )

  slide_count = 0

  content.gsub!( /<div[^>]*>\s*<h1/ ) do |match|
    slide_count += 1
    "\n<!-- _S9SLIDE_ -->\n#{Regexp.last_match(0)}" 
  end

  puts "  Adding #{slide_count} slide breaks (using div_h1 rule)..."

  content
end

  
end  # module SlideFilter
end # module Slideshow

class Slideshow::Gen
  include Slideshow::SlideFilter
end