module GitHub::Markup

def can_render?(filename)
  !!renderer(filename)
end

def command(symbol, command, regexp, name, &block)
  if File.exist?(file = File.dirname(__FILE__) + "/commands/#{command}")
    command = file
  end
  markup_impl(symbol, CommandImplementation.new(regexp, command, name, &block))
end

def markup(symbol, file, pattern, opts = {}, &block)
  markup_impl(symbol, GemImplementation.new(pattern, file, &block))
end

def markup_impl(symbol, impl)
  if markups.has_key?(symbol)
    raise ArgumentError, "The '#{symbol}' symbol is already defined."
  end
  markups[symbol] = impl
end

def markup_impls
  markups.values
end

def markups
  @@markups
end

def preload!
  markup_impls.each do |markup|
    markup.load
  end
end

def render(filename, content = nil)
  content ||= File.read(filename)
  if impl = renderer(filename)
    impl.render(content)
  else
    content
  end
end

def render_s(symbol, content)
  if content.nil?
    raise ArgumentError, 'Can not render a nil.'
  elsif markups.has_key?(symbol)
    markups[symbol].render(content)
  else
    content
  end
end

def renderer(filename)
  markup_impls.find { |impl|
    impl.match?(filename)
  }
end