xkcd2.heroku.com : Sinatra app to display xkcd comics so that the alt text can be seen

.gems

sinatra
haml

.gitignore

.rvmrc

README.md

xkcd mini

Just a small Sinatra app to show xkcd comics with the mouseover text visible at the bottom of the page. xkcd.heroku.com does the same thing but I find their images are too small sometimes.

config.ru

$: << '.'
require 'xkcd'
run Sinatra::Application

xkcd.rb

require 'net/http'
require 'uri'
require 'sinatra'
require 'json'
require 'haml'

# Blank route for the favicon to keep errors low
get '/favicon.ico' do
  nil
end

# Random gets a random comic
get '/random' do
  current = symbolize_keys(JSON::parse(get_comic_json(:current)))
  current = current[:num]
  random = rand(current) + 1
  # Make sure we don't hit 404, which is XKCD's actual 404 page.
  while random == 404
    random = rand(current) + 1
  end
  redirect "/#{random}"
end

# Index gets the current comic
get '/' do
  return do_comic(:current)
end

get '/:number' do |number|
  return do_comic(number)
end

def do_comic(number)
  begin
    # Get the JSON data
    current = symbolize_keys(JSON::parse(get_comic_json(:current)))
    @data   = symbolize_keys(JSON::parse(get_comic_json(number)))
  rescue
    @data = { :safe_title => "Not Found" }
    return haml :error
  end

  # Turn the "year", "month", and "day" properties into numbers
  [:year, :month, :day].each { |key| @data[key] = @data[key].to_i }
  # Calculate the "previous" and "next" comics, if any
  @data[:previous] = @data[:num] - 1 unless @data[:num] == 1 || @data[:num].nil?
  unless current[:num] == @data[:num]
    @data[:next] = @data[:num] + 1 unless @data[:num].nil?
  end

  # Make sure we don't hit 404, which is XKCD's actual 404 page.
  @data[:previous] -= 1 if @data[:previous] == 404
  @data[:next]     += 1 if @data[:next]     == 404

  # Render the page
  haml :comic
end

# If the comic number is 0, get today's comic
# Else get the given comic
def get_comic_json(number)
  if number == :current
    Net::HTTP.get(URI.parse("http://xkcd.com/info.0.json"))
  else
    Net::HTTP.get(URI.parse("http://xkcd.com/#{number}/info.0.json"))
  end
end

# change string keys into symbols
def symbolize_keys(arg)
  case arg
  when Array
    arg.map { |elem| symbolize_keys elem }
  when Hash
    Hash[
      arg.map { |key, value|
        k = key.is_a?(String) ? key.to_sym : key
        v = symbolize_keys value
        [k,v]
      }]
  else
    arg
  end
end

__END__

@@ layout
%html
  %head
    %title xkcd mini: #{@data[:safe_title]}
  %body
    = yield

@@ error
%h1 Not Found
%p
  That comic was not found.
%p
  %a{:href => "/"}Home

@@ comic
%h1= @data[:safe_title]
%p
  - unless @data[:previous].nil?
    %a{:href => "/1"}<
      &lt;&lt; First
    &nbsp;|&nbsp;
    %a{:href => "/#{@data[:previous]}"}<
      &lt; Previous
  - else
    &lt;&lt; First
    &nbsp;|&nbsp;
    &lt; Previous
  &nbsp;|&nbsp;
  %a{:href => "/random"}<
    Random
  &nbsp;|&nbsp;
  - unless @data[:next].nil?
    %a{:href => "/#{@data[:next]}"}<
      Next &gt;
    &nbsp;|&nbsp;
    %a{:href => "/"}<
      Last &gt;&gt;
  - else
    Next &gt;
    &nbsp;|&nbsp;
    Last &gt;&gt;
%p
  %img{:src => @data[:img]}
%p= @data[:alt]
%hr
%p
  Read this comic on
  %a{:href => "http://xkcd.com/#{@data[:num]}"}xkcd.com

Pretty slick! Ruby really is about minimal effort, isn't it? I had to look up the whole Sinatra thing...it's cool!

in the post END data there, I guess the "layout" and "comic" labels are magic for haml?

Magic for Sinatra, actually. Looks like Sinatra doesn't even depend on the DATA stream; it reads the file and then splits on __END__. https://github.com/sinatra/sinatra/blob/aa06ed/lib/sinatra/base.rb#L900-923

So I'm guessing sinatra defines the :comic symbol on line 39 when it parses the template and sees "@@ comic"? Sorry if my line number is off...there is a rendering bug in Firefox that causes the line number gutter to be vertically offset.

Yeah, it looks like it creates a hash, using symbols created from whatever's after @@ as the key and all the lines up to the next line that matches /^@@\s*(.*\S)\s*$/ as the value. The haml call just wraps a call to render and passes in :haml as the rendering engine to use. https://github.com/sinatra/sinatra/blob/aa06ed/lib/sinatra/base.rb#L377-379

Cool!