require 'sax-machine'

# Class for parsing an atom entry out of a feedburner atom feed
class AtomEntry
  include SAXMachine
  element :title
  # the :as argument makes this available through atom_entry.author instead of .name
  element :name, :as => :author
  element "feedburner:origLink", :as => :url
  element :summary
  element :content
  element :published
end

# Class for parsing Atom feeds
class Atom
  include SAXMachine
  element :title
  # the :with argument means that you only match a link tag that has an attribute of :type => "text/html"
  # the :value argument means that instead of setting the value to the text between the tag,
  # it sets it to the attribute value of :href
  element :link, :value => :href, :as => :url, :with => {:type => "text/html"}
  element :link, :value => :href, :as => :feed_url, :with => {:type => "application/atom+xml"}
  elements :entry, :as => :entries, :class => AtomEntry
end

# you can then parse like this
feed = Atom.parse(xml_text)
# then you're ready to rock
feed.title # => whatever the title of the blog is
feed.url # => the main url of the blog
feed.feed_url # => goes to the feedburner feed

feed.entries.first.title # => title of the first entry
feed.entries.first.author # => the author of the first entry
feed.entries.first.url # => the permalink on the blog for this entry
# etc ...

# you can also use the elements method without specifying a class like so
class SomeServiceResponse
  elements :message, :as => :messages
end

response = SomeServiceResponse.parse("<response><message>hi</message><message>world</message></response>")
response.messages.first # => "hi"
response.messages.last  # => "world"