A crude script to convert Textile documents to AsciiDoc. Some of the replacements are specific to markup that I use, but hopefully still useful.

textile2asciidoc.rb

#!/usr/bin/env ruby

if ARGV[0].nil?
  $stderr.puts 'Must specify an input file'
  exit 1
end

source = IO.read(ARGV[0])

title = nil
author = nil

# map Awestruct and Jekyll front matter to AsciiDoc attribute entries
source.gsub!(/^---\n(.*?)\n^---/m) {
  fm = $1
  fm.gsub!(/^(\w+): (.*)/, ':\1: \2')
  fm.gsub!(/:title: "([^"]+)"\n/) { title = $1; '' }
  fm.gsub!(/:author: (.*)\n/) { author = $1; '' }
  "#{fm}\n"
}

# p(lead). text
source.gsub!(/^p\((.*?)\)\. /, "[role=\\1]\n")

# bq. text or p((. text
source.gsub!(/^(?:p\(\(|bq)\. (.*)/, "____\n\\1\n____")

# h2. text
source.gsub!(/^h2\. /, '== ')

# h3. text
source.gsub!(/^h3\. /, '=== ')

# h4{margin-top: -1em}. text (specific to my documents)
source.gsub!(/^h4{margin-top: -1em}\. /, "[discrete, role=byline]\n==== ")

# # text (numbered bullets)
source.gsub!(/^# /, '. ')

# - label := def
source.gsub!(/^- (.*?) := (.*)/, '\1:: \2')

# *NOTE*: text
source.gsub!(/^\*(NOTE|TIP):\* /, '\1: ')

# "target":uri
source.gsub!(/\[?"([^"]+)":(https?:\/\/[^\s,\)\]]+)\]?/) {
  suffix = ''
  text = $1
  url = $2
  if url.end_with?('.') || url.end_with?('!')
    suffix = "#{suffix}#{url[-1]}"
    url.chop!
  end

  "#{url}[#{text}]#{suffix}"
}

# @text@
source.gsub!(/@([^@]+)@/, '+\1+')

# !/images/image.png(alt text)! (alt text optional)
# p=. !/images/image.png(alt text)! (alt text optional)
source.gsub!(/(p=\. )?!(?:\((.*?)\))?\/images\/([^\(]+?)(?:\(([^\)]+)\))?!/) {
  block = $~.pre_match.end_with?("\n") && $~.post_match.start_with?("\n")
  pos = $1
  role = $2
  uri = $3
  text = $4
  buf = "image#{block ? '::' : ':'}#{uri}["
  if text
    buf = "#{buf}#{text}"
  end

  if !role && pos && pos.end_with?('.')
    if text
      buf = "#{buf}, "
    end
    buf = "#{buf}role=ctr"
  end

  if role
    if text
      buf = "#{buf}, "
    end
    buf = "#{buf}role=#{role}"
  end

  buf = "#{buf}]"
  buf
}

# bc. code
source.gsub!(/bc\. (.*?)^$/m, "....\n\\1....\n")

# p. text
source.gsub!(/p\. (.*)/, '\1')

# "text"
source.gsub!(/"([^"]+)"/, "``\\1''")

# <sup>text</sup>
source.gsub!(/<sup>(.*?)<\/sup>/, '^\1^')

# reverse order of _ and * around text
source.gsub!(/_\*([^\*]+)\*_/, '*_\1_*')

# output document
puts "= #{title}\n"
puts "#{author}\n"
puts source