#!/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -wKU
# == Synopsis
#
# gen_html: generates HTML file from markdown and optional template(s)
#
# == Usage
#
# gen_html [OPTION] ... [FILE]
#
# --help:
#    show help
#
# -t/--title «title»
#    make «title» available to template (as `page_name`)
#
# -h/--header «file»
#    prepend «file» as header (erb)
#
# -f/--footer «file»
#    append «file» as footer (erb)
#
# FILE: The markdown document to read (defaults to stdin)

require 'getoptlong'
require 'rdoc/usage'
require 'erb'

def expand_tpl(path, binding)
  ERB.new(File.read(path), 0, '%-<>').result(binding)
end

def find_exe(cmd)
  dir = ENV['PATH'].split(':').find { |dir| File.executable? File.join(dir, cmd) }
  dir ? "#{dir}/#{cmd}" : nil
end

opts = GetoptLong.new(
  [ '--title',  '-t', GetoptLong::REQUIRED_ARGUMENT ],
  [ '--header', '-h', GetoptLong::REQUIRED_ARGUMENT ],
  [ '--footer', '-f', GetoptLong::REQUIRED_ARGUMENT ],
  [ '--help',         GetoptLong::NO_ARGUMENT       ]
)

title, header, footer = 'untitled', nil, nil

opts.each do |opt, arg|
  case opt
    when '--help'
      RDoc::usage
    when '--header'
      header = arg
    when '--footer'
      footer = arg
  end
end

MARKDOWN_COMPILERS = %w[ multimarkdown maruku Markdown.pl ]

filter = MARKDOWN_COMPILERS.find { |exe| find_exe exe }
abort "Unable to find a markdown compiler" if filter.nil?

filters    = "|#{filter}"

document   = ARGF.read
head, body = document.scan(/\A((?:^\w+:\s+.*$\n)*)\n?((?m:.*))\z/).flatten
tmp        = head.scan(/^(\w+):\s+(.*)$/).collect { |pair| [pair[0].downcase, pair[1].strip] }
headers    = Hash[*tmp.flatten]

page_title = headers['title'] || title
css_files  = headers['css'].to_s.split(/,\s*/)
js_files   = headers['js'].to_s.split(/,\s*/)
meta_data  = Hash[*headers['meta'].to_s.scan(/(.*?)="(.*?)"(?:,\s*)?/).flatten]

STDOUT << expand_tpl(header, binding) unless header.nil?
STDOUT << open(filters, 'r+') { |io| io << document; io.close_write; io.read }
STDOUT << expand_tpl(footer, binding) unless footer.nil?