#!/System/Library/Frameworks/Ruby.framework/Versions/Current/usr/bin/ruby
# == 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)
$KCODE = 'U' if RUBY_VERSION < "1.9"

require 'optparse'
require 'erb'

def expand_tpl(str, binding)
  ERB.new(str, 0, '%-').result(binding)
end

def expand_tpl_file(path, binding)
  expand_tpl(File.read(path), binding)
end

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

def wrap_key_equivalents(src)
  src.gsub(/ `([^`]+⇥)` | \( ([⌃⌥⇧⌘↓↑←→]+) \) | ( [⎋⇥↩⌅⌫⌦] | [⌃⌥⇧⌘]+ ( (?=[ ]|-\w+) | F\d+ | . ) ) /x) do
    if $1
      "<kbd class='tabTrigger'>#$1</kbd>"
    elsif $2
      "(<kbd class='keyEquivalent'>#$2</kbd>)"
    else
      "<kbd class='keyEquivalent'>#$&</kbd>"
    end
  end
end

def wrap_authors(src)
  src.gsub(/ \*\[ (.+?) \]\* /x) do
    "<span class='credit'>#$1</span>"
  end
end

def wrap_in_article(html)
  html.gsub(/<h2\b.*>.*<\/h2>(?m:.*?)(?=\s*<h2|\z)/) do
    "<article>\n#$&\n</article>\n"
  end
end

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

OptionParser.new do |opts|
  opts.banner = "Usage: gen_html [options] [file]"
  opts.separator "Synopsis:"
  opts.separator "gen_html: generates HTML file from markdown and optional template(s)"
  opts.separator "Options:"

  opts.on("-?", "--help", "show help.") do |v|
    puts opts
    exit
  end

  opts.on("-h","--header FILE", "prepend «file» as header (erb)") do |arg|
    header = arg
  end

  opts.on("-f","--footer FILE", "append «file» as footer (erb)") do |arg|
    footer = arg
  end

  opts.on("-t","--title TITLE", "make «title» available to template (as `page_name`)") do |arg|
    title = arg
  end

  opts.on("-w","--warn", "enable warnings") do |arg|
    warn = true
  end
end.parse!

MARKDOWN_COMPILERS = %w[ multimarkdown ]

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

filters    = "|#{filter} --nosmart"

document   = ARGF.read
document   = wrap_authors(wrap_key_equivalents(document))
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_file(header, binding) unless header.nil?
STDOUT << open(filters, 'r+') { |io| io << body; io.close_write; wrap_in_article(expand_tpl(io.read, binding)) }
STDOUT << expand_tpl_file(footer, binding) unless footer.nil?