Very first working version of app.

Lots of effort put in here by @danbernier:

https://github.com/danbernier/hacketyhack/blob/5f595199621cbc906edb4048d4abc76c6fe4c050/app/ui/lessons.rb\#L366

This became the basis for my renderer.

Author: steveklabnik

lib/hackety_hack/lessons/app.rb

@@ -0,0 +1,97 @@
+# encoding: utf-8
+Shoes.setup do
+  gem 'redcarpet'
+  gem 'hackety_hack-lessons', '1.1.1'
+end
+require 'redcarpet'
+require 'hackety_hack/lessons'
+
+class Renderer < Redcarpet::Render::Base
+  def initialize(app)
+    super()
+    @app = app
+    @args = []
+  end
+
+  def header(text, level)
+    case level
+    when 1
+      @app.instance_eval { para text, :size => "x-large" }
+    when 2
+      @app.instance_eval { para text, :size => "large" }
+    when 3
+      @app.instance_eval { para text }
+    end
+    ''
+  end
+
+  def image(path, title, alt_text)
+    on_click = if alt_text.nil? || alt_text.empty?
+                 Proc.new {}
+               else
+                 Proc.new { alert(alt_text) }
+               end
+
+    @app.instance_eval { image("http://hackety.com#{path}", {}, &on_click) }
+    ''
+  end
+
+
+  def emphasis(text)
+    store @app.em(text)
+  end
+
+  def double_emphasis(text)
+    store @app.strong(text)
+  end
+
+  def link(link, title, content)
+    store @app.link(content, :click => link)
+  end
+
+  def codespan(code)
+    store @app.code(code)
+  end
+
+  def store(shoes_bit)
+    @args << shoes_bit
+    '[-]'
+  end
+
+  def paragraph(text)
+    para_bits = interpolate(text, @args)
+
+    @app.instance_eval { para *para_bits, :font => "TakaoGothic" }
+    @args.clear
+    ''
+  end
+
+  # The markdown string "I'd _love_ a cupcake!" comes to us looking like this:
+  # "Hello, I'd [-] a cupcake!"
+  # ...and @args looks like this:
+  # [Shoes::Em]
+  # #interpolate turns them into this:
+  # ["Hello, I'd ", Shoes::Em, " a cupcake!"]
+  # These are the args that'll be passed to Shoes#para.
+  # It also turns "_I_ like _chocolate!_" into
+  # [Shoes::Em, " like ", Shoes::Em]
+  def interpolate(text, args)
+    results = []
+    while text.include?('[-]')
+      head, text = *text.split('[-]', 2)
+      results << head << args.shift
+    end
+    results << text 
+    results << args unless args.empty?
+
+    return results.compact
+  end
+end
+
+Shoes.app do
+  renderer = Renderer.new(self)
+  markdown = Redcarpet::Markdown.new(renderer, fenced_code_blocks: true)
+  stack do
+    markdown.render(File.read("../../../content/an-introduction-to-ruby-with-hackety-hack.md", :encoding => "utf-8"))
+  end
+end