page.rb

require 'haml'
require 'time'

# base
class Base
  def initialize(opts)
    @opts = opts
    %w(title description).each do |var|
      eval "def #{var}=(v)\n @opts[:#{var}]=v\nend"
      eval "def #{var}\n @opts[:#{var}]\nend"
    end
  end

  def html
    hash = { lang: 'en' }
    hash['⚡'] = '' if @opts[:amp]
    hash
  end

  def css(name)
    if @opts[:amp]
      '<style amp-custom="amp-custom">' +
      File.read("target/css/#{name}") +
      '</style>'
    else
      "<link type='text/css'
        href='/css/#{name}?#{@opts[:revision]}'
        rel='stylesheet'/>"
    end
  end

  def youtube(id)
    if @opts[:amp]
      "<amp-youtube data-videoid='#{id}'
        layout='responsive' width='480' height='270'></amp-youtube>"
    else
      "<iframe class='video'
        src='https://www.youtube.com/embed/#{id}?controls=2'
        frameborder='0' allowfullscreen='yes'>&#8203;</iframe>"
    end
  end

  def input(path)
    Page.new(File.read(path), @opts).html
  end
end

# Page to render
class Page
  def initialize(haml, opts)
    @haml = haml
    @opts = opts
  end

  def html
    engine = Haml::Engine.new(
      @haml,
      format: :xhtml,
      style: :indented
    )
    @opts[:published] = Time.now unless @opts.key?(:published)
    engine.render(Base.new(@opts), @opts)
  end
end